Clinical presentation depending on species and subspecies
The symptomatology and localization of the pathological process are determined by which specific microorganism caused the infection.
Classic Friedländer's bacillus (K. pneumoniae subsp. pneumoniae) It is one of the leading causative agents of healthcare-associated infections (HAIs), predominantly affecting the respiratory and urinary tracts. It exhibits pronounced multidrug resistance to antibacterial drugs.
- Causes non-specific respiratory tract infections (bronchitis, pneumonia).
- Affects the urinary system.
- Causes foodborne toxic infections.
- Responsible for purulent-septic complications: postpartum and neonatal complications (intestinal infections, pneumonia, and sepsis with high mortality in newborns).
Specific subspecies of K. pneumoniae
- K. pneumoniae subsp. ozaenae: localizes on the mucous membrane of the nose and paranasal sinuses. A characteristic clinical symptom is the discharge of foul-smelling secretions (a condition known as ozena).
- K. pneumoniae subsp. rhinoscleromatis: the causative agent of rhinoscleroma (affecting the upper respiratory tract). Pathomorphologically, the process manifests as the formation of granulomas followed by sclerotic tissue changes. The disease has a chronic course, which is associated with the microbe's ability to reside intracellularly.
Other significant species
- K. oxytoca: frequently causes healthcare-associated infections in urological practice.
- K. granulomatis: the causative agent of donovanosis (granuloma inguinale). The infection is endemic to tropical climates and is transmitted primarily sexually (less frequently through household contact). It manifests as ulceration of granulomatous lesions of the skin and subcutaneous tissue.
Features of the immune response
Immunity in Klebsiella infections has several specific features. The humoral response on its own does not possess protective activity. The body's primary defense mechanism is phagocytosis of the bacteria, but only after their preliminary opsonization by specific antibodies.
In chronic forms of infection, such as rhinoscleroma, the microbe resides inside host cells for a long time. Such intracellular persistence leads to the development of delayed-type hypersensitivity (DTH).
Microbiological diagnostics
The choice of diagnostic method directly depends on the clinical form of the disease and the suspected localization of the pathogen.
- Bacteriological method (primary). Material for examination may include sputum, urine, feces, blood, or pus. Inoculation is performed on lactose-containing differential nutrient media. The main goal is to isolate a pure culture of the pathogen and accurately identify it to the species or subspecies level.
- Serological method. Consists of performing the complement fixation test (CFT) using a specific O-antigen.
- Bacterioscopic method. Used specifically for the diagnosis of donovanosis. The studied material is a granuloma biopsy sample stained with Giemsa stain. The main diagnostic sign is the detection of Donovan bodies in smears.
Treatment and Prevention
Specific prophylaxis for Klebsiella infections has not currently been developed; vaccines against these pathogens do not exist.
To treat infections, Klebsiella bacteriophage and antibacterial drugs are used. Due to the presence of potent virulence factors in Klebsiella in the form of multiple drug resistance, the prescription of antibiotics must be carried out strictly based on the results of an antibiogram.
Briefly: answers to topical questions
What are the morphological and tintorial properties of Klebsiella (Gram stain, shape, presence of a capsule, motility)?
Klebsiella are small to medium Gram-negative bacilli that stain red with the Gram stain.
- Shape — rod-shaped (dimensions 1–5 $\times$ 0.4–0.8 µm).
- Gram stain — Gram-negative.
- Motility — may be non-motile.
- Capsule — capable of forming a capsule, do not form spores.
What pathogenicity (virulence) factors are distinguished in Klebsiella?
Several main pathogenicity factors are distinguished in Klebsiella that contribute to the development of infection and resistance to therapy.
- Multidrug resistance — multiple resistance to antibiotics.
- Adhesiveness — provided by fimbriae (pili) that allow attachment to uroepithelial cells.
- Antiphagocytic activity — caused by capsular K-antigens that block opsonization and phagocytosis.
- Hemolysin production — stimulates colony growth and increases resistance to antibiotic therapy.
On which specific differential diagnostic media is inoculation performed to isolate a pure culture of Klebsiella?
To isolate a pure culture of Klebsiella, inoculation is performed on lactose-containing differential media. These media include:
- Endo agar — used for Enterobacteriaceae.
- Levine's EMB agar — used for Enterobacteriaceae.
What antigens are distinguished in the antigenic structure of Klebsiella?
In the antigenic structure of Klebsiella, as typical representatives of the Enterobacteriaceae family, two main types of antigens are distinguished, which have important diagnostic and pathogenetic significance.
- O-antigen — a somatic thermostable antigen used in serological diagnosis (e.g., when performing the CFT).
- K-antigen — a capsular polysaccharide antigen that determines the antiphagocytic activity of the bacteria.
Ozena stinks, scleroma turns to stone: K. ozaenae causes a foul-smelling rhinitis (ozena), while K. rhinoscleromatis causes granulomas progressing to tissue sclerosis.
Class and exam questions
Can a Klebsiella infection be prevented with a vaccination?
No, specific prophylaxis has not been developed, and a vaccine does not exist.
Why is an antibiogram so important in the treatment of Klebsiella infections?
Because classic species of Klebsiella (especially K. pneumoniae) exhibit multiple drug resistance to antibiotics.
What else to study on this topic
- Mechanisms of multidrug resistance development in K. pneumoniae
- Pathomorphological features of rhinoscleroma at different stages
- The role of Klebsiella in the structure of healthcare-associated infections (HAIs)
- Pathogenesis of Donovan body formation in K. granulomatis infection
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