Clostridioides difficile (C. difficile)-associated enterocolitis: clinical guidelines

List of Abbreviations

GI – gastrointestinal tract

SCFA – short-chain fatty acids

IBD – inflammatory bowel disease

NAP1/B1/027 (North American pulsed-field gel electrophoresis type 1, restriction endonuclease analysis type B1, polymerase chain reaction ribotype 027) – a hypervirulent strain of C. difficile, named after its typing method (North American pulsed-field gel electrophoresis type 1, restriction endonuclease analysis type B1, polymerase chain reaction ribotype 027)

IBS – irritable bowel syndrome

HIV – human immunodeficiency virus

GDH – glutamate dehydrogenase

PCR – polymerase chain reaction

IA — immunochromatographic assay

EIA – enzyme immunoassay

US – ultrasound examination

MSCT – multislice computed tomography

CMV — cytomegalovirus

FMT – fecal microbiota transplantation

RCT – randomized controlled trial

GIT – gastrointestinal bleeding

IL – interleukin

NF-κB – nuclear factor kappa B

OR – odds ratio

CI – confidence interval

AII – acute intestinal infection

Terms and Definitions

Disease – a disorder of body function, working capacity, and the ability to adapt to changing environmental and internal conditions arising from the impact of pathogenic factors, accompanied by a simultaneous alteration of the body's protective-compensatory and protective-adaptive reactions and mechanisms.

Instrumental diagnostics – diagnostics utilizing various devices, apparatus, and instruments for patient examination.

Disease outcomes – medical and biological consequences of a disease.

Clinical situation – a case requiring standardization of medical care regardless of the disease or syndrome.

Laboratory diagnostics – a set of methods aimed at analyzing test material using various specialized equipment.

Disease complication – the addition to a disease of a syndrome of impaired physiological processes; - impairment of the integrity of an organ or its wall; - bleeding; - developed acute or chronic failure of the function of an organ or organ system.

Primary disease is a disease that, by itself or through its complications, creates the primary need for medical care due to the greatest threat to working capacity, life, and health, or leads to disability, or causes death.

Disease relapse – the recurrence or return of clinical manifestations of a disease after their temporary remission or disappearance.

Symptom – any sign of a disease detectable regardless of the method used to determine it.

Syndrome – a condition developing as a consequence of a disease and defined by a set of clinical, laboratory, and instrumental diagnostic signs that allow it to be identified and classified into a group of conditions with diverse etiology but common pathogenesis, clinical manifestations, and general treatment approaches, which nevertheless depend on the underlying diseases of the syndrome.

Concomitant disease is a disease that has no causal relationship with the primary disease, is inferior to it in terms of the need for medical care, impact on working capacity, danger to life and health, and is not the cause of death.

Condition – changes in the body arising due to the impact of pathogenic and/or physiological factors and requiring medical care.

Severity of a disease or condition is a criterion determining the degree of damage to organs and (or) systems of the human body or impairment of their functions caused by a disease or condition or their complication.

Level of certainty of evidence – reflects the degree of confidence that the found effect of a medical intervention is true.

Level of recommendation certainty – reflects not only the degree of confidence in the validity of the intervention's effect, but also the degree of confidence that following the recommendations will bring more benefit than harm in a specific situation.

1. Brief information on the disease or condition

1.1 Definition of the disease or condition

Enterocolitis caused by Clostridioides difficile (C. difficile) – a disease developing with reduced intestinal microbiota diversity and excessive colonization by C. difficile, whose toxins cause damage to the mucosal-epithelial barrier followed by inflammation in the colon wall, with diarrhea being the characteristic clinical manifestation [1].

Pseudomembranous colitis – a severe nonspecific inflammatory disease of the colon resulting from epithelial damage and decreased blood flow to the mucosa, characterized by fibrinous deposits on the colonic mucosa [2, 3, 4, 5].

1.2 Etiology and pathogenesis of the disease or condition (group of diseases or conditions)

The main etiological factor of enterocolitis caused by C. difficile is Clostridioides difficile (C. difficile) – a Gram-positive, obligately anaerobic, spore-forming bacillus. In 2016, an official reclassification was performed, establishing the species Clostridioides difficile separately, which has taxonomic and phylogenetic differences from other members of the genus Clostridium [6, 7]. Both nontoxigenic and toxigenic strains of C. difficile have been described. Nontoxigenic strains belong to ribotypes 847 and 032 and do not cause colonic mucosal inflammation. Toxigenic strains can cause enterocolitis. Several toxigenic strains belong to ribotypes 014, 015, 078, 244, and 027. Among them, ribotypes 027 and 078 are the most clinically significant and associated with the development of severe forms of clostridial infection [8, 9, 10].

The life cycle of C. difficile includes spore germination into vegetative cells, multiplication followed by toxin production, and concludes with the reverse formation of spores, which are necessary for transmission between hosts and survival in the environment. Spores can survive for several months and are resistant to heat, systemic antibacterial drugs, and acidic gastric juice pH (5 and below). Vegetative forms of C. difficile can survive in gastric contents only at a pH of 5 or higher.

Spore maturation into vegetative forms occurs in the distal small intestine and colon due to the combined action of primary bile acid salts (cholate, taurocholate, glycocholate, deoxycholate) and L-glycine. Secondary bile acids (deoxycholic acid and lithocholic acid), conversely, inhibit spore maturation and toxin production. Calcium ions (in vivo) contribute to the activation of signaling pathways that trigger spore germination, while ineffective calcium absorption in the gut increases the risk of clostridial infection [11, 12].

The gastrointestinal tract (GIT) is the natural habitat for toxigenic and nontoxigenic strains of C. difficile in the majority of newborns (15–70%). Over time, as a stable microbiota composition is formed under the influence of natural factors, commensal microorganisms become predominant and provide a protective environment against toxigenic strains of C. difficile through nutrient competition, synthesis of short-chain fatty acids (SCFAs), bacteriocins, antimicrobial peptides, and secondary bile acids. Nevertheless, about 5% of the adult population is colonized by toxigenic strains of C. difficile [5, 11, 13].

However, colonization by C. difficile does not always lead to clinical symptoms or disease development and may remain asymptomatic. The composition of the intestinal microbiota in asymptomatic individuals is similar to that of healthy people. It is hypothesized that the daily risk of progression from asymptomatic colonization to C. difficile-associated enterocolitis decreases over time, which may be mediated by an adaptive immune response manifested by an increase in serum antibody titers against toxins A and B [1, 5].

Risk factors for clostridial infection may be due to the patient's condition (e.g., immune status, multimorbidity), the possibility of infection by C. difficile spores (hospitalization, stay in residential social care facilities), and disruption of the intestinal microbiota composition (use of systemic antibacterial drugs, other medications, surgical interventions).

Alteration of the intestinal microbiota composition, primarily during the administration of systemic antibacterial drugs, leads to colonic colonization by toxigenic strains of C. difficile, which is considered the first stage of the infection. Other risk factors associated with altered intestinal microbiota composition include age >65 years, use of proton pump inhibitors, and comorbidities (inflammatory bowel disease (IBD), diabetes mellitus, obesity) [5, 13]. The main changes in intestinal microbiota composition consist of decreased diversity, a reduction in Ruminococcaceae, Bifidobacterium, Faecalibacterium, and an increase in Proteobacteria, Bacteroidetes, and Clostridium spp., which increases the risk of C. difficile-associated enterocolitis by 10-fold [1]. The pathogen itself is non-invasive; its virulence is due to the production of toxin A (TcdA) and toxin B (TcdB), as well as enzymes such as collagenase, hyaluronidase, and chondroitin sulfatase [11]. Traditionally, toxin A was considered an "enterotoxin" playing a dominant role by disrupting the mucosal-epithelial barrier and allowing toxin B, a "cytotoxin," to enter enterocytes and the lamina propria to exert toxic effects. However, more recent data indicate that both toxins are capable of causing colonic wall damage through the direct destruction of epithelial cells and tight junctions.

Increased permeability of the mucosal-epithelial barrier promotes the activation of the innate immune response and the production of pro-inflammatory cytokines, followed by epithelial cell apoptosis and necrosis. Impairment of the intestinal barrier combined with immune system activation stimulates increased fluid secretion. It is hypothesized that toxin B possesses more potent pro-inflammatory activity and is capable of causing a more severe form of the disease than toxin A, but both toxins can induce symptoms independently of each other. The hypervirulent C. difficile NAP1/B1/027 strain is characterized by increased production of toxins A and B, and also produces a specific binary toxin, TcdC. The binary toxin is considered an "enterotoxin" and is capable of increasing the virulence of C. difficile in the presence of toxins A or B by inducing pathogen colonization, the production of pro-inflammatory cytokines, and suppressing the host's protective eosinophilic response. The production of this toxin in addition to C. difficile toxins A and B is associated with severe disease, higher mortality, and a risk of recurrence. Cases of severe Clostridioides infection caused by a strain producing only the binary toxin have been described [3, 5]. It is believed that an impaired immune response to C. difficile toxins, as well as new contact with spores, contributes to the development of disease recurrences [5, 8]. Strains of C. difficile associated with the development of hospital-acquired and community-acquired infection do not differ [14, 15].

Toxigenic C. difficile is also the most well-known etiological factor of pseudomembranous colitis, which develops during severe courses of clostridial infection. At the same time, C. difficile-induced enterocolitis and pseudomembranous colitis are not interchangeable terms. Possible etiological factors of pseudomembranous colitis can also include other infectious agents (Staphylococcus aureus, Escherichia coli, cytomegalovirus, cryptosporidia), medications (nonsteroidal anti-inflammatory and antirheumatic drugs, chemotherapeutic agents), certain large bowel diseases (microscopic colitis, inflammatory bowel disease (IBD), ischemic colitis), and systemic vasculitides (Behçet's disease). The disease develops as a result of reduced oxygenation, damage to the colonic epithelium, and impaired blood flow to the mucous membrane, followed by the formation of pseudomembranes on the mucosa consisting of necrotic epithelial cells, fibrin, mucus, and leukocytes [2, 3, 4, 5].

1.3 Epidemiology of the Disease or Condition

C. difficile is a major cause of diarrhea in hospitalized individuals. In the late 20th century, the incidence of clostridial infection increased in many countries worldwide, and currently, this disease is classified among the most significant nosocomial infections [5].

The source of C. difficile infection can be either patients or healthy bacterial carriers. The transmission mechanism is fecal-oral, realized via contact-household, waterborne, and less commonly foodborne routes. Transmission factors include patient care items, instruments, various nosocomial objects, and, most importantly, the hands of medical personnel and caregivers [1, 5, 10, 11].

During the first days of hospitalization, the rate of C. difficile acquisition with the potential development of clinical symptoms ranges from 2.1% to 20% and increases with the duration of hospital stay. After one month in the hospital, the acquisition rate may increase up to 50%. However, only 25–30% of colonized patients develop diarrhea [5]. The prevalence of asymptomatic carriage among healthy individuals, hospitalized patients, and long-term care patients is < 2%, 3–26%, and 5–7%, respectively [10]. The probability of a non-colonized healthy person acquiring C. difficile in a healthcare facility is 2.3%, in long-term care facilities 0.37%, and outside a healthcare facility 0.12%. The probability of a healthy non-colonized person acquiring the infection from a patient with C. difficile-associated disease outside a healthcare facility is 0.1%, and from an asymptomatic colonized person, 0.05% [15].

The increase in morbidity, the development of more severe forms of C. difficile-associated disease, and mortality in the late 20th century were caused by the emergence of the epidemic hypervirulent strain NAP1/B1/027, whereas other strains were identified in asymptomatic carriers [10, 15]. The risk of infection recurrence is 10–35%, with a subsequent increase in the risk of repeated recurrences up to 65% after each episode. Up to 75–85% of cases of C. difficile-induced enterocolitis recurrence are associated with an overgrowth of colony-forming units (CFUs) of the same strain. Reinfection is caused by a new strain [10, 15, 17].

In the Russian Federation, C. difficile infection was detected in 34.4% of cases of antibiotic-associated diarrhea in patients at multidisciplinary hospitals in Saint Petersburg [18].

Overall, there is currently a slowdown and stabilization in the overall incidence of C. difficile-induced enterocolitis worldwide, which is explained by the rapidly declining prevalence of the hypervirulent strain NAP1/B1/027 against the background of improved diagnostic algorithms and treatment regimens, as well as the expansion of antimicrobial stewardship programs. The total number of clostridial infection cases globally decreased from 476,400 in 2011 to 462,100 in 2017. In the USA, 223,900 cases of C. difficile-induced enterocolitis and 12,800 deaths were registered in 2017. Nevertheless, overall mortality directly from clostridial infection is estimated at 5%, while mortality due to complications reaches 15–25%, and up to 34% in intensive care units [5, 13, 15]. The total number of C. difficile-induced enterocolitis recurrences has also decreased and remains stable. For instance, in the USA, this figure dropped from 93,400 to 69,800 between 2011 and 2017. However, over the past decade, there has been an increase in community-acquired C. difficile infection [8, 10, 19], which accounts for 10% to 43% of registered C. difficile infection cases [8, 10, 15]. According to recent data in the USA, the incidence of community-acquired clostridial infection increased from 52.88 per 100,000 population in 2012 to 65.93 per 100,000 population in 2017. In Canada, this figure increased from 6.09 to 9.56 per 100,000 population per year over the period 2005–2015 [15, 20]. Patients with community-acquired infection tend to be younger (mean age 50 years), have lower mortality rates (0.07%), and a significant proportion (36%) have no history of systemic antibacterial drug use [15].

Thus, the expansion of C. difficile infection risk groups among both patients and healthy individuals, the potential development of complications (including fatal ones), the persistent risk of recurrence and reinfection, fairly high morbidity and mortality rates, and the growth of community-acquired infection determine the high relevance of studying prevention and treatment measures for this disease [15, 16].

1.4 Features of Coding the Disease or Condition

A04.7 Enterocolitis due to Clostridium difficile

K52.8.0 – Pseudomembranous colitis

1.5 Classification of the disease or condition

There is no universally accepted classification for C. difficile-induced enterocolitis.

Depending on the association of symptom onset with medical care and/or hospitalization, community-acquired and hospital-acquired infections are distinguished. Hospital-acquired C. difficile infection is characterized by the onset of symptoms 48 hours or more after hospitalization. Community-acquired infection, accordingly, manifests as the onset of symptoms outside a hospital setting. The onset of symptoms within 12 weeks after hospital discharge is considered healthcare-associated C. difficile infection. The onset of symptoms within the first 48 hours after hospitalization or no less than 12 weeks after hospital discharge is considered a community-acquired C. difficile infection. Such a distinction emphasizes the risks of developing Clostridioides infection, which is important from an epidemiological perspective [8,10].

Depending on the presence of clinical symptoms, their severity, and complications, C. difficile asymptomatic carriage, mild/moderate, and severe/complicated courses of C. difficile-induced enterocolitis are distinguished [1, 5, 10, 21]. Currently, there are no validated criteria for assessing the severity of C. difficile-induced enterocolitis [10, 21]. Mild/moderate cases are generally characterized by diarrhea without signs of systemic infection [21]. A severe/complicated course is characterized by fever (> 38.5 °C), leukocytosis (> 15 × 10⁹ / L), and elevated creatinine levels (> 1.5 mg / dL) [10]. Table 1 summarizes the main signs that allow the classification of various severity degrees of clostridial infection.

Table 1. Manifestations of C. difficile-induced enterocolitis depending on severity [8, 10, 22, 23, 24, 25, 26]

*Watery diarrhea is absent in patients with ileus and toxic megacolon

** Summarizes additional symptoms that may occur in patients with varying severity of C. difficile-induced enterocolitis

Depending on the time of symptom onset and their relation to previous episodes of clostridial infection, primary episode, relapse, and reinfection are distinguished. The primary episode is characterized by the onset of symptoms combined with a positive diagnostic test for C. difficile toxins and the absence of signs of clostridial infection within the preceding 8 weeks [10]. Relapse is characterized by the recurrence of symptoms and a positive test result following temporary resolution of symptoms with standard treatment of the primary episode in the preceding 2–8 weeks, most commonly within the first week after treatment [10]. C. difficile reinfection is the onset of symptoms and a positive stool test for toxins during standard treatment of the primary episode, associated with infection by a new C. difficile strain. The time threshold for distinguishing between relapse and reinfection ranges from 8 to 20 weeks [8, 10, 15].

1.6 Clinical presentation of the disease or condition

The clinical presentation of C. difficile-induced enterocolitis can range from asymptomatic carriage, self-limiting mild or moderate diarrhea, to profuse watery diarrhea, pseudomembranous colitis, intestinal obstruction, toxic megacolon, bowel perforation, sepsis, and patient death [5, 15, 16, 21]. (see Table 1)

The main clinical symptom is considered to be diarrhea (≥ 3 episodes of loose stools per day) within 24 hours [8].

C. difficile can affect any part of the colon, but inflammation most frequently develops in the distal segments [5]. The incubation period can last more than one week (up to 28 days), averaging 2–3 days. In most patients, the main clinical symptom is mild diarrhea (up to 5 times per day), with spontaneous recovery occurring 5–10 days after the discontinuation of systemic antibiotics. Diarrhea most frequently occurs during or immediately after antibacterial therapy [8, 10, 25].

In addition to diarrhea, abdominal pain, fever, nausea and vomiting, weakness, and loss of appetite may occur. The fecal occult blood test is frequently positive, although active gastrointestinal bleeding is rare. In rare cases, signs of reactive arthritis may be present. In the most severe cases, symptoms such as dehydration, hypoalbuminemia with peripheral edema, and subsequent hypovolemic shock come to the forefront of the clinical picture. Severe complications of C. difficile-induced enterocolitis include toxic megacolon, colonic perforation, intestinal paresis, renal failure, systemic inflammatory response syndrome, septicemia, and death [5, 10].

The clinical presentation of pseudomembranous colitis is characterized by diarrhea, cramping abdominal pain, and fever. The disease may proceed with the development of complications such as electrolyte imbalances, ileus, megacolon, gastrointestinal bleeding, and colonic perforation [2, 4, 5].

It should be noted that colonized patients may also experience diarrhea unrelated to C. difficile-induced enterocolitis. Clinical features pointing toward an alternative diagnosis include lack of response to treatment in non-severe cases, atypical course (including chronic diarrhea), periodicity and lack of negative symptom dynamics without treatment, and a history of alternating diarrhea and constipation [27].

2. Diagnostics, medical indications and contraindications for diagnostic methods

Diagnosis of C. difficile-induced enterocolitis is based on the evaluation of the clinical presentation, medical history, physical examination of the patient, and laboratory testing of stool samples. Identifying target patient groups for clostridial infection diagnostics is important in preventing overdiagnosis and subsequent unwarranted treatment — testing for C. difficile should be performed only in patients with new-onset diarrhea within 24 hours (loose stools, Bristol type 6-7 scale , at least 3 times a day) with no other apparent cause of diarrhea. When intestinal obstruction is suspected, obtaining a rectal swab sample is acceptable. An important diagnostic sign is the presence of a proven risk factor (in particular, recent antibiotic therapy, advanced age, hospitalization). Disease severity is determined by clinical symptoms and laboratory findings. Additional diagnostic methods performed according to indications to help assess severity include colonoscopy and abdominal imaging methods. When diagnosing C. difficile-induced enterocolitis, it is necessary to assess not only the severity, but also whether the episode is primary, a relapse, or a reinfection [5, 8, 10, 21, 25, 27].

Criteria for establishing the diagnosis/condition: the diagnosis and severity of C. difficile-induced enterocolitis are established based on clinical, anamnestic, laboratory, and instrumental data.

2.1 Complaints and Anamnesis

Complaints typical for patients with C. difficile-induced enterocolitis are described in Table 1 (Section 1.5 "Classification") and Section 1.6 "Clinical Presentation".

Comments: first of all, the intake of laxatives during the preceding 48 hours after symptom onset should be ruled out. Other non-infectious causes of diarrhea include the use of chemotherapy, enteral nutrition, abdominal surgery, and concomitant diseases such as IBD and irritable bowel syndrome (IBS). At the same time, these conditions and diseases can themselves be risk factors for clostridial infection [8, 25]. Advanced age, hospital admission, and antibiotic therapy are considered the main risk factors for C. difficile-induced enterocolitis. The use of systemic antibacterial drugs is the most important modifiable risk factor that directly affects the composition of the gut microbiota. The prescription of almost all classes of systemic antibacterial drugs is associated with the development of C. difficile-induced enterocolitis, with the highest risk posed by clindamycin**, beta-lactam antibiotics, penicillins, third/fourth-generation cephalosporins, carbapenems, and fluoroquinolones, followed by macrolides, sulfonamides, and trimethoprim [16, 25]. It is believed that the disruption of the gut microbiota composition caused by systemic antibacterial drugs is long-lasting, and the risk of developing C. difficile-induced enterocolitis increases both during therapy and for up to 3 months after its completion. During therapy with systemic antibacterial drugs and within the first month after it, the risk of clostridial infection increases by 7–10 times, and by 3 times in the subsequent 2 months. The risk of clostridial infection is directly proportional to the duration of intake and the number of systemic antibacterial drugs. Nevertheless, even short-term exposure to a systemic antibacterial drug, for example, as a prophylactic measure in surgical interventions, increases the risk of C. difficile colonization and the development of symptoms in the patient [5, 8, 10, 13, 28]. Proven risk factors for C. difficile-induced enterocolitis also include: immunodeficiency states (IBD, HIV, cancer, post-organ transplantation states, and consequently, the use of immunosuppressive and chemotherapy drugs), gastrointestinal surgeries (especially bowel resection), tube feeding, concomitant comorbidities (renal failure, diabetes mellitus, cystic fibrosis, cardiovascular and respiratory diseases), and reduced gastric acidity (primarily due to proton pump inhibitors and H2-receptor antagonists) [5, 8, 10, 25]. It has been shown that long-term use of proton pump inhibitors reduces gut microbiota diversity and can double the risk of C. difficile infection. The incidence of C. difficile-induced enterocolitis in individuals receiving proton pump inhibitors is 65%–75% higher than in the general healthy population. However, this risk factor remains controversial. Firstly, diarrhea is a known side effect of proton pump inhibitors. Secondly, studies and systematic reviews demonstrating an increased incidence of clostridial infection in patients receiving proton pump inhibitors often failed to adjust for confounding factors such as advanced age, comorbidities, and the use of systemic antibacterial drugs, which may bias the results [27]. Risk factors for recurrence of C. difficile-induced enterocolitis include the prescription of systemic antibacterial drugs during or after treatment of the first episode, advanced age (≥ 65 years), female sex, a history of C. difficile-induced enterocolitis episodes (risk of recurrence after a primary episode is 20%, after two episodes is 40%, and after three is 65%), comorbidities (chronic kidney disease, IBD), immunosuppressive therapy, nasogastric tube feeding, and reduced gastric acidity (prolonged use of proton pump inhibitors or H2-receptor antagonists) [10, 15]. Prognostic risk factors for severe/complicated disease are detailed in Section 7 (Additional Information).

2.2 Physical Examination

Physical examination findings vary depending on the severity of enterocolitis caused by C. difficile (Table 1). In mild-to-moderate cases, patients may present with mucus or blood in the stool, low-grade fever, and mild abdominal tenderness. In severe/complicated cases, various clinical symptoms may be observed, including high-grade fever, diffuse abdominal pain, abdominal distension, and hypovolemia (dry skin and mucous membranes, decreased skin turgor). Abdominal inspection may reveal distension, palpation shows diffuse tenderness, and percussion reveals tympany. It is important to note that patients with severe C. difficile enterocolitis may develop paralytic ileus, which can delay diagnosis and, if the condition progresses, lead to toxic megacolon or colonic perforation. Patients with a complicated course of the disease are hemodynamically unstable, and signs of hypotension, shock, impaired consciousness, peritonitis, and systemic inflammatory response syndrome may be detected [21, 25, 26].

2.3 Laboratory Diagnostics

Comments: if a patient presents with diarrhea that cannot be fully explained by an underlying condition (IBD) or ongoing treatment (enteral tube feeding, chemotherapy, laxative use), it is advisable to perform laboratory testing for C. difficile. Testing is indicated if symptoms persist despite the discontinuation of therapy (e.g., chemotherapy drugs, laxatives) or enteral tube feeding [10, 25]. In patients with intestinal obstruction, rectal swab samples are recommended for testing [5, 27].

Comments: it is advisable to screen patients without diarrhea for clostridial infection, except for pre-admission testing in cancer hospitals or transplant units for infection control purposes [27].

Comments: culture, molecular genetic, and immunological tests are used to diagnose Clostridioides difficile infection by detecting C. difficile in stool through identification of the pathogen itself, its antigens, toxins, or the glutamate dehydrogenase (GDH) enzyme.

The culture method allows for the detection of C. difficile vegetative cells or spores, assessment of C. difficile cytotoxicity using a neutralization assay on cell culture, and determination of antimicrobial susceptibility. (Table 2).

Polymerase chain reaction (PCR) can detect the pathogen's DNA, genes encoding GDH, as well as toxins A, B, and binary toxin, thereby confirming the presence of a toxigenic C. difficile strain.

The immunochromatographic assay (ICA), an immunological method, is used to detect C. difficile toxin A and B antigens.

Table 2. Diagnostic methods for C. difficile [8, 10, 25, 26, 27, 29, 30].

Currently, it is considered that none of the available laboratory tests are suitable as a standalone diagnostic method for C. difficile-associated enterocolitis. Each has its own procedural and interpretive characteristics, as well as varying sensitivity, specificity, and consequently, predictive value (Table 3). The culture method is labor-intensive, time-consuming, can only be performed in well-equipped laboratories by qualified personnel, and despite its reliability, is rarely used in routine practice [8, 10]. PCR detection of Clostridioides difficile DNA in stool samples has high sensitivity and specificity. This test confirms the presence of C. difficile, but has limitations in use, specifically high cost and difficulties in result interpretation. This method is qualitative (positive or negative) and cannot characterize the bacterial load and viability of C. difficile. The detection of toxin-encoding genes does not always mean the strain is currently producing them. If the diarrhea has another etiology, detecting such a strain may mislead the clinician [5, 8, 27, 29]. Immunochromatographic stool testing for Clostridioides difficile toxins A and B is currently considered the most widespread method due to its low cost and ease of performance. Disadvantages include a high rate of false-positive results and inter-laboratory variability. ICA results for C. difficile toxins may be negative in early stages (due to low bacterial load) and in patients with a complicated disease course. When examining stool samples by immunological methods, transport and storage rules must be followed. Once obtained, a stool sample should be stored at +4 °C (in a refrigerator) and tested within the next 24 hours, because the toxin rapidly degrades at room temperature and becomes undetectable in the specimen after approximately 2 hours [5, 8, 10, 25, 27, 29]. Detecting GDH in stool is also possible using immunological methods, but it does not differentiate whether the patient harbors a toxigenic strain, as GDH is an enzyme produced by non-toxigenic strains as well. Therefore, this test is recommended only as a screening tool.

Commercial ICA test systems have been developed for rapid analysis in the form of plastic strips with wells for sample application, result reading, and control, allowing the detection of not only fecal GDH but also toxins A and B. These tests are easy to use, provide rapid results, and do not require specially trained medical personnel, but they are inferior in sensitivity to other immunoassay methods and lack clear criteria for data interpretation [5, 8, 10, 27, 30, 31]. Currently in Russia, according to the State Register of Medical Devices and Organizations (Individual Entrepreneurs) Engaged in the Production and Manufacture of Medical Devices (www.roszdravnadzor.gov.ru), there is 1 registered reagent kit (rapid test) for the detection of C. difficile GDH + toxin A + toxin B antigens in stool samples by ICA, 2 reagent kits (rapid tests) for the detection of toxin A + toxin B antigens in stool samples by ICA, 4 in vitro diagnostic reagent kits for toxins A and B by ELISA, and 1 in vitro diagnostic reagent kit for toxins A and B using a PCR analyzer. Culture media, supplements, and media components for the microbiological diagnosis of C. difficile are also registered.

Table 3. Characteristics of diagnostic methods used for C. difficile [8, 10, 26, 27, 29, 31].

Comments:

As a primary step/screening, it is recommended to detect C. difficile DNA (PCR) or, if available, GDH (ICA, EIA, PCR). In case of negative tests, clostridial infection is excluded, and further testing is discontinued. If a positive result is obtained, the next recommended step is a test to detect toxins A and B (ICA or EIA). A positive result of the second test confirms the presence of clostridial infection. In case of a negative result of the second test, a thorough clinical evaluation is necessary, as this laboratory picture may occur in three situations: C. difficile with a toxin level below the detection threshold, a false-negative ICA or EIA result for toxins A and B, or C. difficile carriage. Stool samples with a negative GDH result but a positive toxin result must be re-tested, as this result is invalid (see Appendix B) [5, 27].

Comments: re-testing within 7 days after the initial negative result is not recommended due to the high risk of false-positive results, very low diagnostic value (2%), and the likelihood of unnecessary treatment [5, 8, 10, 25]. Re-testing for C. difficile can be considered only in case of clinical deterioration in patients with a characteristic clinical picture and negative primary laboratory test results [10].

Comments: depending on the severity and presence of complications, the complete blood count may show an elevated leukocyte count (leukocytosis), while the general clinical biochemical blood analysis may show an elevated C-reactive protein level, hypoalbuminemia, and markers of acute kidney injury. In mild/moderate cases of C. difficile-induced enterocolitis, blood tests may show leukocytosis up to 15 × 10⁹ / L, and a creatinine level of no more than 1.5 mg/dL. In severe/complicated cases, the complete blood count may show signs of leukocytosis (more than 15 × 10⁹ / L), and the biochemical blood analysis may reveal signs of target organ dysfunction, namely an increase in creatinine of more than 1.5 mg/dL or more than 1.5 times the baseline level. Such patients may exhibit signs of electrolyte imbalance, hypovolemia, and signs of lactic acidosis. In the event of complications, markers of systemic inflammation (CRP) also increase, and hypoalbuminemia develops. If hypotension develops, signs of target organ dysfunction secondary to hypoperfusion, such as elevated liver enzymes, may be observed [10, 25, 27].

Comments: C. difficile is the most common healthcare-associated infection, characterized by an increased incidence of complications associated with blood coagulation disorders, such as deep vein thrombosis (DVT) and disseminated intravascular coagulation (DIC), as well as significant mortality associated with sepsis [34]

Comments: Molecular biological examination of feces for the presence of RNA/DNA of the leading spectrum of acute intestinal infection pathogens is characterized by high sensitivity (over 90%) and specificity (over 95%), and allows to significantly reduce the time required to establish the etiological diagnosis, determine etiological treatment tactics, and carry out anti-epidemic measures in the focus (in case of registered focal incidence). Since the clinical symptoms of infections caused by various enteropathogens largely overlap, it is difficult to differentiate the etiology of diarrhea in patients at the initial medical consultation stage. This problem also applies to the diagnosis of C. difficile infection, which can cause both mild diarrhea and severe pseudomembranous colitis. The results of examining diarrhea patients presenting to the emergency department using viral and bacterial enteric PCR panels and C. difficile PCR made it possible to identify, along with C. difficile (20% of patients), a whole spectrum of classic infectious diarrhea pathogens (Campylobacter spp., Salmonella spp., enterotoxigenic E. coli, Shigella spp., rotavirus, norovirus, etc.) [35].

2.4 Instrumental Diagnostics

Comments: abdominal imaging modalities (plain abdominal radiography, abdominal ultrasound (comprehensive), and contrast-enhanced CT of the abdomen with IV bolus injection) are not the methods of choice for diagnosing Clostridioides difficile infection. They play a significant role in diagnosing complications. Additional imaging modalities are not required in patients with mild-to-moderate C. difficile enterocolitis. When performed in such patients, these methods may reveal distended bowel loops and colonic wall thickening. Ultrasound imaging is particularly effective for monitoring the colonic luminal diameter. Plain abdominal radiography can detect dilation of small and large bowel loops, air-fluid levels within the bowel, and free intraperitoneal air. Oral and intravenous contrast-enhanced CT is effective in patients with severe clostridial infection to identify toxic megacolon, bowel perforation, or other complications requiring surgical intervention. The presence of colonic wall thickening on contrast-enhanced CT of the abdomen with IV bolus injection in patients with an indistinct clinical picture and inconclusive laboratory findings has a high predictive value.

Comments: colonoscopy is not indicated in patients with mild-to-moderate C. difficile enterocolitis confirmed by laboratory tests. This examination is indicated when there are diagnostic difficulties in C. difficile enterocolitis in the following clinical scenarios: presence of a typical clinical presentation of C. difficile enterocolitis with negative stool test results; lack of response to standard treatment; suspected alternative diagnosis when direct visualization and/or colonic mucosal biopsy is required. Colonoscopy can be performed upon rapid disease deterioration to determine the urgency of surgical intervention, for example, if bowel obstruction is suspected. In these settings, limited flexible sigmoidoscopy with minimal or no air insufflation is preferred to avoid perforation of the inflamed colon. Pseudomembranes detected during the procedure appear as raised white or yellow plaques, typically about 2 cm in diameter, which are unevenly distributed and separated by normal mucosa. They are not washed off when flushing the bowel walls. The distribution of pseudomembranes can vary, and their absence does not rule out C. difficile infection. Pseudomembranes are rarely seen in recurrent clostridial infection or in patients with inflammatory bowel disease. It should be kept in mind that pseudomembranous colitis can be a manifestation of Behçet's disease, microscopic colitis, IBD, ischemic colitis, or caused by other pathogens (cytomegalovirus, E. coli). Histological examination of the colonic mucosa is not an obligatory prerequisite for diagnosing C. difficile enterocolitis. This study may be useful in the differential diagnosis of diarrhea, specifically to rule out other causes (e.g., microscopic colitis or IBD). If both endoscopic and histopathological findings are normal, C. difficile colonization is unlikely to be the cause of diarrhea.

3. Treatment, including drug and non-drug therapies, diet therapy, and pain management

Treatment should be initiated in the presence of a characteristic clinical picture of C. difficile enterocolitis and positive laboratory stool test results. Patients with complicated clostridial infection must be managed in the intensive care unit. Empirical treatment can be initiated in patients with a characteristic clinical picture, including fulminant onset and symptom progression, despite negative laboratory test results for C. difficile [5, 8]. The choice of drug and regimen depends on the severity of the episode, the presence of complications, and whether the episode is primary, recurrent, or a reinfection (see Section 1.5 "Classification"). Previously, metronidazole** was the first-line drug of choice, and vancomycin** was second-line. However, there is now sufficient evidence supporting the efficacy of vancomycin** as a first-line agent for C. difficile enterocolitis [36]. In addition to lower efficacy in achieving clinical remission compared with vancomycin**, metronidazole** treatment often requires extending therapy up to 14 days due to delayed response, is associated with more frequent recurrences within 30 days post-treatment, and can cause various adverse effects, including neurotoxicity with repeated and prolonged use [8, 26]. In the Russian Federation, vancomycin** is registered as a powder for solution for infusion and oral solution. (according to the State Register of Medicines https://grls.rosminzdrav.ru/Default.aspx). When using the oral solution for C. difficile enterocolitis, a higher standard daily dose (1000 mg) is required [37]. The goal of treatment is clinical improvement, normalization of laboratory parameters, resolution of abnormal abdominal imaging findings (if previously present), restoration of endoscopic appearance (in pseudomembranous colitis), and prevention of disease recurrence.

3.1 Conservative Treatment

3.1.1. General recommendations

Comments: prompt discontinuation of systemic antibacterial drugs that have a causal and temporal relationship with the onset of clinical symptoms plays a pivotal role in the management of clostridial infection of any severity, as their continued use impairs clinical response to therapy and increases recurrence risk. Discontinuation of antibacterial therapy should be considered in all patients with clostridial infection, provided this does not compromise the management of other underlying conditions. Patients with mild diarrhea, normal WBC count, and normal serum creatinine levels who have no risk factors for severe/complicated disease (see Section 7) can be observed for several days to assess the need for additional treatment beyond antibacterial therapy discontinuation [26].

Comments: the decision to initiate empirical treatment for clostridial infection depends on disease severity and the availability of rapid laboratory testing. Empirical treatment can also be initiated in the presence of a characteristic clinical picture but negative initial laboratory test results [5]. In all other cases, antibacterial therapy for clostridial infection should be started only after laboratory confirmation of the diagnosis to prevent inappropriate use of systemic antibacterial agents and the associated emergence of multidrug-resistant strains [10].

Comments: The use of drugs that reduce colonic motility is not recommended due to the risk of complications such as colonic dilatation, perforation, and, consequently, increased mortality. Although several cohort studies have shown no significant increase in the risk of complications with these drugs, and prospective and randomized studies are lacking, international clinical guidelines do not recommend administering motility-lowering agents in patients with enterocolitis caused by C. difficile [38].

3.1.2 Mild-to-moderate C. difficile enterocolitis

Comments: Compared with #Metronidazole**, #Vancomycin** has minimal systemic absorption, making it suitable for pregnant and lactating women. For patients with IBD or immunodeficiencies, #Vancomycin** at a standard dose is recommended as the first-line drug. However, in IBD, the duration of therapy should be at least 14 days, and escalating the ongoing immunosuppressive therapy should be considered if there is no clinical response to clostridial infection treatment [27].

Comments: If #Vancomycin** is unavailable or contraindicated, #Metronidazole** may be used as an alternative only in mild disease without risk factors for severe disease (see Section 7).

Comments: Rifaximin has demonstrated in vitro antimicrobial activity against C. difficile, making it a potential alternative treatment option. Furthermore, it does not negatively impact the composition of the intestinal microbiota and promotes the growth of Lactobacillus. However, currently, there is insufficient evidence to recommend it as a first-line alternative drug for treating patients with mild-to-moderate clostridial infection. Data regarding its superiority over #Vancomycin** or #Metronidazole** are also lacking [8]. According to a cross-sectional study, Rifaximin showed efficacy in this patient group when there was no response to #Metronidazole** treatment [40]. Further high-quality studies are needed.

3.1.3 Severe enterocolitis caused by C. difficile

Comments: in patients with severe clostridial infection and impaired small bowel transit, intravenous #Metronidazole** may be administered, as the drug is metabolized in the liver and excreted via the biliary tract into the small intestine.

3.1.4 Complicated C. difficile enterocolitis

Comments: for a long time, high-dose oral #Vancomycin** has been the drug of choice in patients with complicated clostridial infection, but despite this, high-quality evidence is lacking [10]. This is primarily due to the lack of high-quality randomized trials, as complicated clostridial infection is rare [29].

Comments: #Vancomycin** enemas should be administered with caution due to the risk of colonic perforation [8]. It is also not fully understood whether a sufficient amount of the drug reaches beyond the left colon with this route of administration [10].

Comments: when administered intravenously, #Metronidazole** can achieve therapeutic concentrations in the inflamed colonic wall [10].

3.1.5 Recurrent enterocolitis caused by C. difficile

It is estimated that a quarter of patients will experience at least one more episode after treatment with #Metronidazole** or #Vancomycin**. Subsequent episodes may be caused by the previously treated strain (relapse) or colonization with a new strain (reinfection) in the presence of risk factors (see Section 2.1 "History"). Regardless of the strain, the treatment is the same [8, 26]. To determine the optimal treatment strategy, it is important to differentiate a first recurrence from recurrent disease with more than one episode [29].

Treatment of the first recurrence of C. difficile enterocolitis

Comments: the results of several studies have shown that pulse therapy and tapering of #Vancomycin** in patients with recurrent clostridial infection provide treatment efficacy of up to 74%, especially if the initial episode was treated with a standard 10-day course of standard doses of #Vancomycin** or #Metronidazole** [8, 41]. Prolonged #Vancomycin** therapy is intended to eradicate vegetative spores that remained dormant during the 10-day treatment course [8]. #Metronidazole** is not recommended for treating recurrent clostridial infection because initial and sustained response rates are lower than those for #Vancomycin** [10].

Treatment of subsequent recurrences of C. difficile enterocolitis

Comments: research results suggest that prescribing Rifaximin after the main course of treatment may be an effective measure to reduce recurrence rates. According to international guidelines, #Rifaximin should be prescribed after the main course of treatment at a dosage of 400 mg 3 times a day for 10 or 20 days. However, the question of its appropriateness, dosage, and duration remains controversial, especially among patients at high risk of recurrence [42]. In a small RCT, patients received #Rifaximin at a dose of 400 mg 3 times a day or placebo for 20 days immediately after completing standard therapy. Recurrence of diarrhea occurred in 7 of 33 (21%) patients receiving #Rifaximin and in 17 of 35 (49%) patients receiving placebo (p = 0.018). Recurrences of *Clostridioides difficile* infection occurred in 5 of 33 (15%) patients receiving #Rifaximin and in 11 of 35 (31%) patients receiving placebo (p = 0.11) [43]. In another study, a 4-week course of #Rifaximin (400 mg 3 times a day for 4 weeks, or 400 mg 3 times a day for the first 2 weeks followed by 200 mg 3 times a day for the subsequent 2 weeks) significantly reduced the risk of recurrence over the subsequent 12 weeks [42]. Further high-quality studies are needed. One of the potential concerns associated with the use of Rifaximin is the possibility of resistance development [10, 44].

3.2 Surgical Treatment

Comments: surgical intervention affects the prognosis of patients with complicated *Clostridioides difficile* infection. Indications for surgical treatment include toxic megacolon, ileus, colonic perforation, peritonitis, septic shock, and systemic inflammatory response syndrome. Additional factors associated with increased mortality that serve as markers of severity and indications for surgery include leukocytosis ≥25×10⁹/L and elevated lactate levels ≥5 mmol/L. Surgical treatment may be considered in cases of failure of all conservative methods of treatment [26]. A systematic review showed that the strongest predictors of postoperative mortality are preoperative intubation, acute renal failure, multiorgan failure, and shock requiring adrenergic and dopaminergic agents. Total colectomy with creation of an ileostomy was associated with the lowest rates of mortality and reoperation. However, less extensive surgical procedures may be considered for patients with early-stage disease [8].

Comments: subtotal colectomy is a generally accepted method of surgical treatment in patients with megacolon, colonic perforation, acute abdomen, as well as in patients with septic shock and associated multiorgan failure, reducing the risk of mortality [10, 26]. Despite the significant scope of the procedure (removal of the greater part of the infected colon), this surgical method avoids an anastomosis with the remaining part of the rectum by creating an ileostomy, with the potential future possibility of closing the patient's stoma [27].

Comments: this alternative surgical method was proposed relatively recently, in 2011. It involves the creation of a diverting loop ileostomy with intraoperative antegrade colonic lavage followed by postoperative intraluminal administration of #Vancomycin** 500 mg in 500 mL of compound sodium lactate solution [potassium chloride + calcium chloride + sodium chloride + sodium lactate] every 8 hours through the ileostomy for 10 days [45]. This method preserves the colon and is less invasive (performed laparoscopically). Despite the advantages of this method and its efficacy, further studies are needed to confirm its effectiveness [10, 26, 45]. The results of a retrospective study including 3,201 patients with *Clostridioides difficile* infection were published, among whom 613 underwent loop ileostomy and 2,408 underwent subtotal colectomy. No significant differences in in-hospital mortality were found (25.96% and 31.18%, respectively, p = 0.28) [46]. The decision regarding the scope of surgical treatment is made by the surgeon.

3.3 Other Treatment

Over the past few decades, thanks to numerous studies, fecal microbiota transplantation (FMT) has gained popularity and is currently a rapidly developing therapeutic field [8]. The fundamental concept is the delivery of physiological fecal microbiota from the stool of a healthy donor into the intestine of a patient with *Clostridioides difficile* infection to correct gut microbiota dysbiosis. Since its first description in 1983, numerous systematic reviews and RCTs have demonstrated the efficacy and safety of this treatment method in patients with recurrent *Clostridioides difficile* infection. FMT was included in earlier international clinical guidelines for the treatment of recurrent Clostridioides difficile infection, and its efficacy is also suggested in patients with severe/complicated disease who do not respond to a standard course of therapy when surgical treatment is not feasible [10, 24, 27]. Several methods of delivering healthy donor samples have been studied: via a nasogastric/nasojejunal tube, colonoscopic infusion, enemas, and oral capsules containing frozen or lyophilized microbiota. All methods have been shown to have a good safety profile and similar efficacy rates (ranging from 82% to 95% after one or two transplantations in most studies) [8]. However, it remains unclear from published studies which route of administration is more effective due to the lack of randomized controlled trials. Each method has its own advantages and disadvantages. For example, tube administration offers low cost and no need for sedation, but precludes examination of the colonic mucosa; colonoscopy involves sedation and invasiveness, but allows visualization of the colonic mucosa and biopsy collection; enemas are simple and non-invasive, but fail to reach the left colon; and capsules are non-invasive and simple, but incur a high cost. As a rule, FMT is well tolerated by patients and has minimal short-term side effects, such as abdominal pain, bloating, diarrhea, and constipation. More severe complications associated with stool sample transfer have also been described, such as colonic microperforation, gastrointestinal bleeding (GIB), and peritonitis [47]. The long-term consequences of altering the gut microbiota via FMT are unknown. Given the diversity of donor stool sources, there may be an overgrowth of bacteria of currently unknown significance and uncultivable bacteria, which could lead to unforeseen consequences for the recipient's health. In 2012, a study involving 77 patients was conducted in which FMT recipients were monitored for 3 months. Four of them (5%) developed autoimmune or rheumatological diseases. However, there is no definitive evidence of a causal relationship between FMT and the development of these diseases, which requires further study [48]. The complexity of performing FMT lies in the lack of standardized protocols for screening and selecting stool samples, as well as standardized criteria for donor selection. Careful selection of a healthy donor is a critical step in preventing iatrogenic transmission of infections [8, 47]. Phase III clinical trials are currently underway to further investigate the efficacy and feasibility of using FMT as a first-line treatment for Clostridioides difficile infection [8].

Comments: there is compelling evidence to consider FMT for the treatment of patients with severe/complicated *Clostridioides difficile* infection who do not respond to a standard course of treatment (within 48–72 hours) and who are not candidates for surgery. FMT may contribute not only to increased treatment efficacy but also to a reduced risk of colectomy, sepsis, and mortality. A single FMT procedure may not be sufficient to achieve a sustained response, and multiple consecutive procedures in rapid succession (every 3–5 days) may be required. There is currently no clear protocol regarding FMT regimens. Clinical data exist on the possibility of resuming #Vancomycin** therapy between FMT procedures in this patient group to increase treatment effectiveness, or performing FMT early after diagnosis against the background of the main course of treatment [27].

Comments: clinical studies in patients with recurrent *Clostridioides difficile* infection have shown a significant disruption in gut microbiota diversity, as well as in the relative abundance of bacterial populations [10]. It has been shown that the efficacy of FMT surpasses standard antibacterial therapy in terms of clinical effectiveness and lower recurrence rates [8, 50, 51]. Furthermore, administering FMT after #Vancomycin** treatment is superior to #Vancomycin** monotherapy in patients with recurrent *Clostridioides difficile* infection [8, 51].

3.4 Assessment of treatment efficacy

Comments: depending on the severity of clostridial infection, evaluation of treatment efficacy includes assessing the dynamics of clinical symptoms (normalization of stool, relief of abdominal pain, normalization of body temperature, disappearance of signs of dehydration), laboratory parameters (in particular, normalization of leukocyte count in the complete blood count), and indicators from additional instrumental examinations (bowel wall thickness and lumen diameter according to comprehensive ultrasound examination of the abdominal organs, and computed tomography of the abdominal organs). Nonspecific fecal inflammatory markers (calprotectin, lactoferrin) are not suitable as a tool for evaluating treatment efficacy.

Comments: repeat testing as a test of cure is not recommended due to the high risk of false-positive results, very low diagnostic value (2%), and the likelihood of unnecessary prolonged treatment, since more than 60% of patients may have positive results even after treatment due to asymptomatic spore shedding for up to 6 weeks [5, 8, 10, 25]. Also, in approximately 25% of cases following treatment for clostridial infection, post-infectious irritable bowel syndrome, diarrheal or mixed subtype, may develop [27].

4. Medical Rehabilitation and Sanatorium-Resort Treatment

Medical rehabilitation measures are aimed at preventing complications and adverse consequences of surgical treatment.

In mild or moderate cases of the disease, treatment is carried out on an outpatient basis. Severe or complicated cases of the disease require hospitalization in a 24-hour inpatient facility with an intensive care unit.

In patients who required surgical treatment for enterocolitis caused by C. difficile, rehabilitation in three stages is possible.

Stage 1 – early rehabilitation, carried out immediately after surgical treatment from the 2nd to the 14th day. The main objective of stage 1 rehabilitation is to restore normal GI tract function after surgical intervention. It is at this stage that urinary disorders are most frequently detected and must be corrected. An important role is also assigned to homeostasis control, measures aimed at healing postoperative wounds, management of postoperative pain, and patient mobilization. During this period, monitoring of the complete blood count, blood biochemistry, coagulogram, and urinalysis is performed.

Stage 2 of rehabilitation begins after 15 days and continues as needed thereafter. It is aimed at the final healing of postoperative wounds with monitoring of the activity of the GI tract and other body systems. This stage can be carried out both on an outpatient basis and in a day or 24-hour inpatient setting.

Stage 3 of rehabilitation is carried out in the late rehabilitation period in patients prior to reconstructive surgery. The main objective at this stage is the compensation of GI tract function, and measures aimed at identifying and correcting the function of the anal sphincter apparatus.

5. Prevention and Dispensary Observation

Preventive measures include the prevention of enterocolitis caused by C. difficile (primary prevention) and disease recurrence (secondary prevention). Considering that C. difficile infection is the most frequent nosocomial infection, and C. difficile spores are highly contagious, preventive measures for spreading the infection within the hospital in established cases of the disease are also distinguished.

5.1 Prevention of the development of enterocolitis caused by C. difficile (primary prevention)

Comments: rational use of systemic antibacterial drugs, namely minimizing the frequency, duration, and number of drugs taken, is the main measure for preventing clostridial infection. The main aspects of such use of systemic antibacterial drugs include prescribing them for the treatment of bacterial rather than viral infections, strictly according to indications, intake of the systemic antibacterial drug by the patient exactly as prescribed by the attending physician, and preference for a systemic antibacterial drug active against a specific microorganism or group of microorganisms rather than broad-spectrum agents [53]. In particular, the intake of fluoroquinolones, clindamycin**, and cephalosporins should be limited [10]. It has also been shown that the incidence of clostridial infection increases in parallel with the increase in the number of systemic antibacterial drugs taken. It has been proven that the rational use of systemic antibacterial drugs is the most cost-effective method for significantly reducing the incidence of clostridial infection [8].

Comments: an earlier meta-analysis and systematic review showed a significant reduction in the risk of developing antibiotic-induced enterocolitis caused by C. difficile, especially in hospitalized patients, when using probiotic strains of Lactobacillus, Saccharomyces, and probiotic mixture strains [55]. A recent meta-analysis evaluated 19 RCTs involving 6,261 patients receiving Saccharomyces boulardii, Lactobacillus spp., Bifidobacterium spp., and Streptococcus spp, of which the probiotic strains Lactobacillus spp., Bifidobacterium spp., and Streptococcus spp. were used alone or in combination. The study showed promising results with a >50% reduction in the incidence of clostridial infection in patients receiving probiotics concomitantly with antibiotics (without specification of the probiotic strain). Furthermore, efficacy was higher when probiotics were administered closer to the first dose of the antibiotic [56].

A direct inhibitory effect on C. difficile toxins is exerted by Saccharomyces boulardii (Saccharomyces boulardii CNCM I-745). This probiotic strain has been shown to inhibit the adhesion of toxin A C. difficile to epithelial cells through the production of a protease that inactivates the receptor for C. difficile toxin A, prevents C. difficile biofilm formation (in vitro), and stimulates the production of antibodies against C. difficile toxin A. In addition, Saccharomyces boulardii CNCM I-745 promotes normalization of the intestinal microbiota composition, increased production of short-chain fatty acids (SCFAs), reduction of the inflammatory response by inhibiting production of the pro-inflammatory cytokine IL-8 and suppressing the nuclear transcription factor κB (NF-κB), as well as the formation of secondary bile acids capable of inhibiting vegetative forms of C. difficile [57, 58, 59, 60]. Saccharomyces boulardii is stable across a wide pH range, including low values, when exposed to bile salts and gastrointestinal enzymes, and is also resistant to antibacterial drugs, as it belongs to a fungal (yeast) species [61].

The results of a large meta-analysis confirm the positive effect of Saccharomyces boulardii in the prevention of the first episode of enterocolitis caused by C. difficile [62]. A recent large cohort study involving 8,763 hospitalized patients showed that patients who received Saccharomyces boulardii concurrently with antibiotic administration had a lower risk of developing clostridial infection (OR = 0.57, 95% CI 0.33–0.96) compared to patients who did not receive Saccharomyces boulardii (p = 0.035), with efficacy being significantly higher with early administration of Saccharomyces boulardii [63].

A probiotic containing the strain Saccharomyces boulardii CNCM I-745 is registered as a medicinal product in the Russian Federation (according to the State Register of Medicinal средств https://grls.rosminzdrav.ru/Default.aspx). It is included in the Practical Guidelines of the Scientific Society for the Promotion of Clinical Study of the Human Microbiome (SSPCM) and the Russian Gastroenterological Association (RGA) on the use of probiotics, prebiotics, synbiotics, and enriched functional foods for the treatment and prevention of gastroenterological diseases in children and adults as a medicinal product for the prevention of antibiotic-associated diarrhea and Clostridioides difficile infection [54]. The recommended dose of Saccharomyces boulardii CNCM I-745 is 5 × 10⁹ CFU twice daily. A limitation for the use of this probiotic is the potential for fungemia in immunocompromised patients, as well as in patients with a CVC (central venous catheter) [61].

Comments: despite clinical data indicating an increased risk of C. difficile-induced enterocolitis with the use of proton pump inhibitors, data heterogeneity, the role of confounding factors, the lack of a dose-response relationship, and other methodological considerations significantly limit their practical application. Like any other medicinal product, proton pump inhibitors should be prescribed strictly according to indications, especially in patients at high risk for Clostridioides difficile infection.

5.2 Prevention of recurrent C. difficile-induced enterocolitis (secondary prevention).

Comments: the use of additional systemic antibacterial drugs (other than those used to treat Clostridioides difficile infection) is associated with an increased risk of prolonged diarrhea and relapse of Clostridioides difficile infection and should therefore be discontinued. However, if such therapy is necessary, it is preferable to choose systemic antibacterial agents associated with a lower risk of Clostridioides difficile infection, such as macrolides, aminoglycosides, sulfonamides, vancomycin**, or tetracyclines.

Comments: patients who require further systemic antibacterial therapy immediately or shortly after treatment for Clostridioides difficile infection are at an increased risk of relapse and complications [10]. In such cases, extension of Vancomycin** treatment or empirical prescription of lower-dose #Vancomycin** (e.g., 125 mg daily) is suggested. However, studies are scarce and their data are contradictory. In one retrospective study, extending the Vancomycin** course beyond 10–14 days showed no positive results in reducing the risk of relapse [66]. Two retrospective cohort studies have been published investigating the risk of Clostridioides difficile infection relapse after successful treatment of a first episode in patients receiving subsequent systemic antibacterial therapy with or without Vancomycin** (with varying doses and regimens) versus no such treatment [67, 68]. Both studies showed a reduced risk of relapse with empirical #Vancomycin** administration during systemic antibacterial therapy for up to 90 days or upon rehospitalization within 1–22 months after treatment of an episode of C. difficile-induced enterocolitis. One study showed a risk reduction in patients with recurrent Clostridioides difficile infection, but not in patients with a single prior episode [68]. Currently, there are no prospective randomized trials on the secondary prevention of Clostridioides difficile infection that could serve as a basis for recommendations, but low-dose #Vancomycin** administration concurrently with systemic antibacterial therapy may be appropriate. Factors influencing the need for such prophylaxis may include the time interval between the treatment of a Clostridioides difficile infection episode and the need for systemic antibacterial therapy, the number and severity of previous episodes, and patient comorbidities [10].

Comments: According to systematic reviews and meta-analyses Saccharomyces boulardii CNCM I-745 has shown good results in preventing further recurrences in patients with recurrent *Clostridioides difficile* infection when added to the main course of treatment [49, 69, 70]. The recommended dose of Saccharomyces boulardii CNCM I-745 is 5 × 10⁹ CFU 2 times a day.

Comments: the recommended dose of oligofructose is 4 g 3 times a day.

Comments: Bezlotoxumab is a fully humanized monoclonal antibody that neutralizes *C. difficile* toxin B. The drug was approved by the FDA (Food and Drug Administration, USA) in 2016 to reduce the risk of recurrence in high-risk patients receiving treatment for *Clostridioides difficile* infection [8, 26]. It is also registered in the Russian Federation (according to the State Register of Medicines https://grls.rosminzdrav.ru/Default.aspx). Two multicenter, placebo-controlled phase III clinical trials showed that patients treated with bezlotoxumab experienced a significant reduction in the rate of *C. difficile*-induced enterocolitis recurrence after 12 weeks of treatment. Although most patients received the drug within 6 days of starting standard antibiotic therapy, there were no differences in the rate of *Clostridioides difficile* infection recurrence depending on the timing of bezlotoxumab infusion [71]. The drug is administered at a dose of 10 mg/kg as an intravenous infusion over 60 minutes without the need for dose adjustment in renal or hepatic impairment. Despite good tolerability, infusion-related reactions were noted in 10% of patients; the drug should be used with caution in patients with heart failure [8]. Research results have shown that the use of bezlotoxumab not only reduces the risk of recurrence, but also the need for FMT (fecal microbiota transplantation), helps reduce 30-day readmissions in patients with one or more risk factors for recurrence, and shortens hospital stays [72, 73]. The efficacy of this drug in reducing the risk of *Clostridioides difficile* infection recurrence does not depend on the choice of antibacterial drug in the standard treatment course, the time of diagnosis, or the time of infusion [74]. Despite the promising properties of the drug, further studies are needed to compare it with FMT and standard antibiotic therapy regarding efficacy, safety, and cost [8, 29].

Comments: patients with Clostridioides difficile infection should be evaluated for the appropriateness of antisecretory therapy. Therapy should be continued if there are corresponding indications.

5.3 Prevention of C. difficile spread in the hospital

Comments: in case of a limited number of single rooms with a dedicated toilet, preference should be given to patients with fecal incontinence. In addition, handwashing and shower facilities should be available to reduce the number of spores on the patient's skin. If placement in a single room is not possible, contact between patients should be avoided (e.g., sharing books/magazines, using the same phone), and the patient must have separate furniture.

Comments: wearing gloves combined with hand hygiene should reduce the concentration of C. difficile on the hands of medical personnel. Care should also be taken to prevent hand contamination when removing gloves. The use of gowns, preferably disposable, has been recommended due to potential contamination of medical staff work uniforms with C. difficile and the high quality of evidence showing a reduction in the transmission of other multidrug-resistant intestinal microorganisms.

Comments: hand hygiene is considered the primary measure for preventing the spread of infection and includes washing hands under running water with soap or an alcohol-based hand rub. However, C. difficile spores have high alcohol resistance; therefore, during a Clostridioides difficile outbreak or upon potential contact with patient stool samples, preference should be given to washing hands with soap and water before and after patient care. It has also been shown that antiseptics containing chlorhexidine** are more effective than soap in eliminating C. difficile spores from the hands of medical personnel, although high-quality clinical studies have not been conducted. It is believed that the degree of surface contamination with C. difficile spores in a medical facility correlates with the degree of hand contamination of medical personnel.

Comments: whenever possible, the use of disposable medical devices is recommended. Reusable medical equipment should be kept in the patient's room. Cleaning and disinfection of reusable equipment should be performed after each contact with a patient with Clostridioides difficile infection. For these purposes, it is preferable to use a sporicidal disinfectant compatible with the equipment used.

Comments: daily cleaning with a sporicidal agent should be considered in conjunction with other measures to prevent Clostridioides difficile infection during outbreaks or when there is evidence of recurrent cases in the same room. Chlorine-based solutions are generally recommended for environmental cleaning, with a chlorine concentration of 1,000 ppm being effective and 5,000 ppm being the optimal choice. After discharge, the patient's room must be thoroughly disinfected.

6. Organization of Medical Care

Medical care for patients with C. difficile-induced enterocolitis is provided in the form of:

• primary health care;

• emergency medical care, including specialized emergency medical care;

• specialized medical care, including high-tech medical care.

For patients with mild C. difficile-induced enterocolitis or suspected disease, medical care is provided as primary outpatient health care by general practitioners, family physicians, gastroenterologists, and infectious disease specialists, who carry out a set of diagnostic and treatment measures, including those aimed at identifying the causative agent and implementing initial anti-epidemic measures carried out by medical personnel of the medical organization.

Specialized care for patients with C. difficile-induced enterocolitis is provided in medical organizations or their structural subdivisions providing specialized medical care (therapeutic, gastroenterological, surgical, and infectious disease departments).

Indications for inpatient hospitalization: due to the acute nature of the disease, emergency hospitalization in a 24-hour inpatient facility is performed in the presence of the following clinical situations:

1) intolerance to oral treatment medications

2) dehydration

3) presence of risk factors for a severe/complicated course of C. difficile-induced enterocolitis.

4) hospitalization or transfer to an intensive care unit is indicated in case of severe disease or development of complications (septic shock, sepsis, toxic megacolon, peritonitis, severe dehydration with hypotension and target organ dysfunction)

Indications for patient discharge from the hospital:

1) Reduction in the severity of clinical symptoms (normalization of stool, body temperature, relief of abdominal pain)

2) Normalization of laboratory parameters

3) Normalization of instrumental examination results, including abdominal imaging (colonic wall thickness) and endoscopic examination (disappearance of pseudomembranes according to colonoscopy in pseudomembranous colitis)

4) Normalization of the function of other organs and systems involved in the pathological process during a complicated course of the disease (e.g., kidneys in the development of renal failure, etc.)

5) Refusal of the patient or their legal representative to receive medical care in a 24-hour inpatient facility

6) Need to transfer the patient to another medical organization of the appropriate medical profile. The conclusion on the feasibility of transferring the patient to a specialized medical organization is made after a preliminary consultation based on provided medical documents and/or a preliminary examination of the patient by medical specialists of the target medical organization.

7. Additional Information

Prognostic factors for a severe/complicated course of C. difficile-induced enterocolitis include: advanced age (≥ 65 years), leukocytosis (> 15 × 10⁹ / L), hypoalbuminemia (serum albumin < 30 g/L), elevated serum creatinine (> 1.5 mg/dL or more than 1.5 times baseline creatinine, or a 25% decrease in glomerular filtration rate compared to baseline), and infection with the hypervirulent NAP1/B1/027 strain. It is important to note that in patients with malignant neoplasms and hematological diseases, leukocyte counts and creatinine levels may tend to decrease. Therefore, not all of the above factors may apply to this group of patients, and a personalized approach is required [10, 29].

Criteria for Evaluating the Quality of Medical Care

References

Appendix A1. Working Group Composition

1. Vladimir T. Ivashkin, Academician of the Russian Academy of Sciences, Professor, Doctor of Medical Sciences, Chief Freelance Gastroenterologist of the Russian Ministry of Health, Head of the Department of Propaedeutics of Internal Diseases, Gastroenterology and Hepatology, Director of the V.H. Vasilenko Clinic of Propaedeutics of Internal Diseases, Gastroenterology and Hepatology, Sechenov First Moscow State Medical University of the Russian Ministry of Health (Sechenov University). President of the Scientific Society for the Promotion of Clinical Research of the Human Microbiome (SSPCRHM), President of the Russian Gastroenterological Association.

2. Nikolay I. Briko, Academician of the Russian Academy of Sciences, Doctor of Medical Sciences, Professor, Chairman of the National Association of Specialists in Healthcare-Associated Infections (NASCI), Head of the Department of Epidemiology and Evidence-Based Medicine, Sechenov First Moscow State Medical University of the Russian Ministry of Health (Sechenov University)

3. Alexander V. Gorelov, Doctor of Medical Sciences, Professor, Academician of the Russian Academy of Sciences, Deputy Director for Research, Central Research Institute of Epidemiology of Rospotrebnadzor

4. Oksana M. Drapkina, Doctor of Medical Sciences, Professor, Academician of the Russian Academy of Sciences, Chief Freelance Specialist in Therapy and General Medical Practice of the Russian Ministry of Health, Director of the National Medical Research Center for Therapy and Preventive Medicine of the Russian Ministry of Health

5. Igor V. Maev, Academician of the Russian Academy of Sciences, Doctor of Medical Sciences, Professor, Vice-Rector for Academic Affairs, First Vice-Rector, Head of the Department of Propaedeutics of Internal Diseases and Gastroenterology, Russian University of Medicine of the Russian Ministry of Health.

6. Yury A. Shelygin, Doctor of Medical Sciences, Professor, Academician of the Russian Academy of Sciences, Honored Doctor of Russia, two-time laureate of the Russian Government Prize in

Science and Technology, Chief Freelance Coloproctologist

of the Russian Ministry of Health, Scientific Advisor of the A.N. Ryzhikh National Medical Research Center of Coloproctology of the Russian Ministry of Health

7. Olga P. Alekseeva, Doctor of Medical Sciences, Professor, Chief Gastroenterologist of the Privolzhsky Federal District. Director of the Regional Gastroenterological Center at the N.A. Semashko Nizhny Novgorod Regional Clinical Hospital.

8. Sergey A. Alekseenko, Doctor of Medical Sciences, Professor, Chief Gastroenterologist of the Far Eastern Federal District. Head of the Department of Hospital Therapy, Far Eastern State Medical University of the Russian Ministry of Health.

9. Dmitry N. Andreev, Candidate of Medical Sciences, Associate Professor at the Department of Propaedeutics of Internal Diseases and Gastroenterology, Russian University of Medicine of the Russian Ministry of Health.

10. Vladimir A. Anokhin, Doctor of Medical Sciences, Professor, Head of the Department of Pediatric Infections, Kazan State Medical University of the Russian Ministry of Health

11. Sergey I. Achkasov, Doctor of Medical Sciences, Professor, Corresponding Member of the Russian Academy of Sciences, Director of the A.N. Ryzhikh National Medical Research Center of Coloproctology of the Russian Ministry of Health

12. Andrey Yu. Baranovsky, Doctor of Medical Sciences, Professor, Chief Freelance Gastroenterologist of the North-West Federal District of the Russian Federation. Head of the Scientific, Clinical and Educational Center of Gastroenterology and Hepatology of Saint Petersburg State University, Chairman of the Saint Petersburg Scientific Society of Gastroenterologists, Hepatologists, and Nutritionists.

13. Oleg V. Goloshchapov, Candidate of Medical Sciences, Head of the ICU No. 3 at the R.M. Gorbacheva Research Institute of Pediatric Oncology, Hematology and Transplantology, Assistant at the Department of Anesthesiology and Intensive Care, Pavlov First Saint Petersburg State Medical University.

14. Alexander A. Derinov, Candidate of Medical Sciences, Associate Professor at the Department of Surgery of the Institute of Clinical Medicine, Head of the Oncological Coloproctology Department at the Clinic of Coloproctology and Minimally Invasive Surgery, Sechenov First Moscow State Medical University of the Russian Ministry of Health.

15. Natalia V. Zheleznova, Chief Freelance Gastroenterologist of the Kursk Region Healthcare Committee, Head of the Gastroenterological Department of the Kursk Regional Clinical Hospital.

16. Oksana Yu. Zolnikova, Doctor of Medical Sciences, Chief Freelance Gastroenterologist of the Central Federal District of the Russian Federation, Professor at the Department of Propaedeutics of Internal Diseases, Gastroenterology and Hepatology, Sechenov First Moscow State Medical University of the Russian Ministry of Health.

17. Vladimir N. Kashnikov, Doctor of Medical Sciences, Deputy Director for Innovative Development, A.N. Ryzhikh National Medical Research Center of Coloproctology of the Russian Ministry of Health

18. Irina L. Klyaritskaya, Doctor of Medical Sciences, Professor, Chief Freelance Gastroenterologist of the Republic of Crimea.

19. Natalia V. Korochanskaya, Doctor of Medical Sciences, Professor, Chief Freelance Gastroenterologist of Krasnodar Krai and the Southern Federal District. Head of the Gastroenterology Center at the Regional Clinical Hospital No. 2 of the Ministry of Health of Krasnodar Krai.

20. Dmitry A. Lioznov, Doctor of Medical Sciences, Professor, Director of the Smorodintsev Research Institute of Influenza of the Russian Ministry of Health

21. Olga S. Lyashenko, Physician at the Gastroenterology Department of the V.H. Vasilenko Clinic of Propaedeutics of Internal Diseases, Gastroenterology and Hepatology, University Clinical Hospital No. 2, Sechenov First Moscow State Medical University of the Russian Ministry of Health.

22. Lyudmila N. Mazankova, Doctor of Medical Sciences, Professor, Head of the Department of Pediatric Infectious Diseases of the Russian Medical Academy of Continuous Professional Education (RMAPO), Chief Freelance Specialist in Pediatric Infectious Diseases of Moscow

23. Roman V. Maslennikov, Candidate of Medical Sciences, Associate Professor at the Department of Propaedeutics of Internal Diseases, Gastroenterology and Hepatology, Sechenov First Moscow State Medical University of the Russian Ministry of Health.

24. Gulnara Kh. Murtazina, Candidate of Medical Sciences, Associate Professor at the Department of Infectious Diseases, Kazan State Medical University of the Russian Ministry of Health

25. Roman G. Myazin, Candidate of Medical Sciences, Associate Professor at the Department of Internal Diseases, Volgograd State Medical University of the Russian Ministry of Health.

26. Irina V. Nikolaeva, Doctor of Medical Sciences, Professor, Head of the Department of Infectious Diseases, Kazan State Medical University of the Russian Ministry of Health

27. Ksenia E. Novak, Candidate of Medical Sciences, Associate Professor at the Department of Adult Infectious Diseases and Epidemiology, Saint Petersburg State Pediatric Medical University of the Russian Ministry of Health

28. Pavel V. Pavlov, Candidate of Medical Sciences, Head of the Department of Diagnostic and Therapeutic Endoscopy at the V.H. Vasilenko Clinic of Propaedeutics of Internal Diseases, Gastroenterology and Hepatology, University Clinical Hospital No. 2, Sechenov First Moscow State Medical University of the Russian Ministry of Health.

29. Marina V. Perekalina, Candidate of Medical Sciences, Chief Freelance Gastroenterologist of Stavropol Krai.

30. Nikita A. Pisarenko, Endoscopist, Gastroenterologist, A.S. Lukashevsky Kamchatka Regional Hospital, Petropavlovsk-Kamchatsky.

31. Anastasia V. Povotreiko, Chief Pulmonologist of the Pskov Region. Chief Physician of the Pskov Regional Infectious Diseases Hospital.

32. Polibin Roman Vladimirovich, Candidate of Medical Sciences, Associate Professor, Executive Director of the National Association of Specialists in Healthcare-Associated Infections (NASCI), Chief freelance specialist epidemiologist of the Russian Ministry of Health, Deputy Director for Research at the F.F. Erisman Institute of Public Health, Sechenov First Moscow State Medical University (Sechenov University).

33. Poluektova Elena Alexandrovna, Doctor of Medical Sciences, Professor at the Department of Propedeutics of Internal Diseases, Gastroenterology and Hepatology, Sechenov First Moscow State Medical University of the Russian Ministry of Health. Vice President of the Scientific Society for the Promotion of Clinical Study of the Human Microbiome (SSCHM).

34. Sekretareva Lada Anatolyevna, Chief Gastroenterologist of the Republic of Mari El, Head of the Gastroenterological Department of the Medical Unit No. 1

35. Sukhina Marina Alekseevna, Candidate of Biological Sciences, Head of the Department of Microbiological and Immunological Research, A.N. Ryzhikh National Medical Research Center of Coloproctology of the Russian Ministry of Health, Leading Researcher at the Laboratory of Microbiology and Parasitology, Center for Strategic Planning and Management of Biomedical Health Risks of the Federal Medical-Biological Agency (FMBA of Russia)

36. Tkachev Alexander Vasilyevich, Doctor of Medical Sciences, Professor, Head of the Department of Propedeutics of Internal Diseases, Rostov State Medical University of the Russian Ministry of Health.

37. Troshkina Yulia Mikhailovna, Chief freelance gastroenterologist of the Tula Region, Head of the Gastroenterological Department of the Tula Regional Clinical Hospital.

38. Trukhmanov Alexander Sergeevich, Doctor of Medical Sciences, Professor, Professor at the Department of Propedeutics of Internal Diseases, Gastroenterology and Hepatology, Sechenov First Moscow State Medical University of the Russian Ministry of Health.

39. Tulina Inna Andreevna, Candidate of Medical Sciences, Associate Professor at the Department of Surgery, Institute of Clinical Medicine, Sechenov First Moscow State Medical University of the Russian Ministry of Health.

40. Ulyanin Anatoly Igorevich, gastroenterologist at the Department of Chronic Intestinal and Pancreatic Diseases, V.Kh. Vasilenko Clinic of Propedeutics of Internal Diseases, Gastroenterology and Hepatology, University Clinical Hospital No. 2, Sechenov First Moscow State Medical University of the Russian Ministry of Health.

41. Usenko Denis Valerievich – Doctor of Medical Sciences, Associate Professor, Leading Researcher at the Clinical Department of Infectious Pathology, Central Research Institute of Epidemiology of Rospotrebnadzor

42. Filatova Svetlana Grigorievna, Chief freelance gastroenterologist of the Tambov Region, Head of the Gastroenterological Department of the V.D. Babenko Tambov Regional Clinical Hospital.

43. Frolov Sergey Alekseevich – Doctor of Medical Sciences, Deputy Director for Research, A.N. Ryzhikh National Medical Research Center of Coloproctology of the Russian Ministry of Health

44. Khaliullina Svetlana Viktorovna – Doctor of Medical Sciences, Professor at the Department of Pediatric Infections, Kazan State Medical University of the Russian Ministry of Health

45. Tsarkov Petr Vladimirovich, Doctor of Medical Sciences, Professor, Head of the Department of Surgery, Institute of Clinical Medicine, Director of the Clinic of Coloproctology and Minimally Invasive Surgery, Sechenov First Moscow State Medical University of the Russian Ministry of Health.

46. Tsukanov Vladislav Vladimirovich, Doctor of Medical Sciences, Professor, Chief freelance gastroenterologist of the Siberian Federal District. Head of the Clinical Department of Digestive System Pathology in Adults, Research Institute of Medical Problems of the North, Federal Research Center "Krasnoyarsk Science Center of the Siberian Branch of the Russian Academy of Sciences".

47. Chulanov Vladimir Petrovich, Doctor of Medical Sciences, Professor at the Department of Infectious Diseases, Faculty of Preventive Medicine, Sechenov First Moscow State Medical University of the Russian Ministry of Health, Deputy Director for Research and Innovative Development, National Medical Research Center for Phthisiopulmonology and Infectious Diseases of the Ministry of Health of the Russian Federation

48. Sheptulina Anna Farokhovna, Candidate of Medical Sciences, Head of the Laboratory of Preventive and Experimental Gastroenterology, Leading Researcher, National Medical Research Center for Therapy and Preventive Medicine of the Russian Ministry of Health, Associate Professor at the Department of Therapy and Preventive Medicine, Russian University of Medicine of the Russian Ministry of Health.

49. Shifrin Oleg Samuilovich, Doctor of Medical Sciences, Professor at the Department of Propedeutics of Internal Diseases, Gastroenterology and Hepatology, Head of the Department of Chronic Intestinal and Pancreatic Diseases, V.Kh. Vasilenko Clinic of Propedeutics of Internal Diseases, Gastroenterology and Hepatology, University Clinical Hospital No. 2, Sechenov First Moscow State Medical University of the Russian Ministry of Health.

50. Esaulenko Elena Vladimirovna, Doctor of Medical Sciences, Professor, Head of the Department of Adult Infectious Diseases and Epidemiology, Saint Petersburg State Pediatric Medical University of the Russian Ministry of Health

Appendix A2. Methodology for Developing Clinical Guidelines

These guidelines aim to provide practitioners with modern concepts regarding the etiology and pathogenesis of C. difficile-associated disease, and to introduce current algorithms for diagnosis, severity assessment, prevention, and treatment

Target audience for these clinical guidelines:

1. gastroenterologists

2. internists

3. infectious disease specialists

4. general practitioners (family physicians)

5. coloproctologists

6. surgeons

7. endoscopists

In these clinical guidelines, all information is ranked by level of reliability (evidence) based on the quantity and quality of studies on the given disease

Table 1.Levels of Evidence (LoE) grading scale for diagnostic methods (diagnostic interventions)

Table 2.Levels of Evidence (LoE) grading scale for prevention, treatment and rehabilitation methods (preventive, therapeutic, and rehabilitative interventions)

Table 3.Grades of Recommendation (GoR) for prevention, diagnostic, treatment and rehabilitation methods (preventive, diagnostic, therapeutic, and rehabilitative interventions)

Procedure for updating clinical guidelines.

The mechanism for updating clinical guidelines provides for their systematic revision at least once every three years, as well as upon the emergence of new evidence-based medicine data on the diagnosis, treatment, prevention, and rehabilitation of specific diseases, or in the presence of justified additions/comments to previously approved clinical guidelines, but no more frequently than once every 6 months.

Appendix A3. Reference Materials

These clinical guidelines were developed taking into account the following regulatory legal documents

1. Federal Law No. 323-FZ of November 21, 2011 (as amended on August 8, 2024) "On the Fundamentals of Protecting the Health of Citizens in the Russian Federation" (with rev. and add., effective from September 1, 2024)

2. Federal Law No. 326-FZ of November 29, 2010 (as amended on December 25, 2023) "On Compulsory Medical Insurance in the Russian Federation"

3. Order of the Ministry of Health and Social Development of Russia No. 541n of July 23, 2010 (as amended on April 9, 2018) "On Approval of the Unified Qualification Reference Book of Posts of Managers, Specialists and Employees, Section 'Qualification Characteristics of Employee Positions in Healthcare'"

4. Order of the Ministry of Health and Social Development of Russia No. 69n of January 31, 2012 "On Approval of the Procedure for Providing Medical Care to Adult Patients with Infectious Diseases"

5. Order of the Ministry of Health of the Russian Federation No. 906n of November 12, 2012 "On Approval ofงาม the Procedure for Providing Medical Care to the Population Profiled in 'Gastroenterology'"

6. Order of the Ministry of Health of the Russian Federation No. 804n of October 13, 2017 "On Approval of the Nomenclature of Medical Services" (as amended on September 24, 2020, with rev. of October 26, 2022)

7. Order of the Ministry of Health of Russia No. 205n of May 2, 2023 "On Approval of the Nomenclature of Positions of Medical Workers and Pharmaceutical Workers"

8. Order of the Ministry of Health of Russia No. 700n of October 7, 2015 "On the Nomenclature of Specialties of Specialists with Higher Medical and Pharmaceutical Education"

9. Order of the Ministry of Health of Russia No. 203n of May 10, 2017 "On Approval of Criteria for Assessing the Quality of Medical Care"

10. Sanitary Rules and Norms (SanPiN) 3.3686-21 "Sanitary and Epidemiological Requirements for the Prevention of Infectious Diseases" No. 4

11. International Classification of Diseases, Injuries and Causes of Death (ICD-10)

12. Methodological Guidelines MU 4.2.2039-05. 4.2. Control Methods. Biological and microbiological factors. Technique for collection and transportation of biological materials to microbiological laboratories. Methodological guidelines (approved by Rospotrebnadzor on December 23, 2005).

13. Methodological Guidelines MUK 4.2.2746-10. 4.2. Control Methods. Biological and microbiological factors. Procedure for applying molecular genetic methods in the investigation of outbreaks of acute intestinal infections with group morbidity. Methodological guidelines (approved by Rospotrebnadzor on September 30, 2010).

14. Methodological Guidelines MU 1.3.2569-09. 1.3. Epidemiology. Organization of work of laboratories using nucleic acid amplification methods when working with material containing microorganisms of pathogenicity groups I-IV. Methodological guidelines (approved by Rospotrebnadzor on December 22, 2009).

15. Clinical guidelines of the National Association of Specialists in Control of Healthcare-Associated Infections and the All-Russian Public Non-Profit Organization "Association of Coloproctologists of Russia" on the diagnosis, treatment, and prevention of Clostridium difficile-associated diarrhea (CDI), 2017.

16. Ivashkin V.T., Lyashenko O.S., Drapkina O.M., Alekseeva O.P., Alekseenko S.A., Andreev D.N., Baranovsky A.Yu., Goloshchapov O.V., Zheleznova N.V., Zolnikova O.Yu., Klyaritskaya I.L., Korochanskaya N.V., Lapina T.L., Maev I.V., Maslennikov R.V., Myazin R.G., Pavlov P.V., Perekalina M.V., Pisarenko N.A., Povotreiko A.V., Poluektova E.A., Sekretareva L.A., Tkachev A.V., Troshkina Yu.M., Trukhmanov A.S., Ulyanin A.I., Filatova S.G., Tsukanov V.V., Shifrin O.S. [Practical guidelines of the Scientific Community for the Promotion of Clinical Studies of the Human Microbiome, the Russian Gastroenterological Association, and the Russian Society for the Prevention of Non-Communicable Diseases on the diagnosis and treatment of Clostridioides difficile (C. difficile)-associated disease in adults]. Rossiyskiy Zhurnal Gastroenterologii, Gepatologii, Koloproktologii. 2023;33(3):85-119. (In Russ.) https://doi.org/10.22416/1382-4376-2023-33-3-85-119

Appendix B. Physician Action Algorithms

Appendix C. Patient Information

Dear patient! C. difficile can inhabit the intestine of a healthy person in small amounts as part of the normal microbiota. Spores of this bacterium can be present on any surface and enter the gastrointestinal tract through ingestion. Therefore, one of the preventive measures is adherence to hygiene rules (e.g., washing hands before meals, especially after visiting medical institutions, and avoiding unwashed food). However, even the presence of the bacterium in the gut or the entry of its spores into the gastrointestinal tract will not lead to disease development in the absence of factors promoting its overgrowth. The primary factor altering the normal composition of the microbiota is the use of systemic antibacterial drugs. It is extremely important to take systemic antibacterial drugs only when truly necessary and strictly as prescribed by a physician, just like any other medications. If you develop diarrhea, you should consult a doctor to determine the need for further evaluation and to receive treatment recommendations. Do not self-medicate. Timely and correct treatment allows for a complete cure and helps avoid complications.

Appendix G. Assessment Scales, Questionnaires, and Other Evaluation Tools

Russian title: Bristol Stool Form Scale

Original title: Bristol Stool Form Scale

Sources: Lewis SJ, Heaton KW. Stool form scale as a useful guide to intestinal transit time. Scand J Gastroenterol. 1997 Sep;32(9):920-4. doi: 10.3109/00365529709011203. PMID: 9299672.; Brian E. Lacy, Fermín Mearin, Lin Chang, William D. Chey, Anthony J. Lembo, Magnus Simren, Robin Spiller. Bowel Disorders. Gastroenterology. Volume 150, Issue 6, 2016, Pages 1393-1407.e5, https://doi.org/10.1053/j.gastro.2016.02.031.

Type (underline):

— rating scale

— index

— questionnaire

— other (please specify):

Purpose: monitoring changes in bowel function and intestinal transit

Content (template):

Key (interpretation):

Types 1 and 2 characterize constipation

Types 3, 4, and 5 characterize normal stool

Types 6 and 7 characterize diarrhea

Notes: the scale is used along with the assessment of defecation frequency and the presence of intestinal symptoms (pain during defecation, feeling of incomplete bowel evacuation)