Vulnerability factors and ports of entry
Immediately after birth, the newborn is physiologically defenseless against massive microbial aggression. High levels of stress glucocorticoids suppress the immune response, skin and mucosal barriers are not yet fully formed, and the body is in a state of transient dysbiocenosis. The situation is further aggravated by the predominance of protein catabolism.
The localization of the primary focus (port of entry) determines the initial clinical picture:
- Gastrointestinal tract: presents with diarrhea or necrotizing enterocolitis. Often associated with the absence of enteral nutrition or nosocomial outbreaks.
- Respiratory system: manifests as ventilator-associated pneumonia in infants on mechanical ventilation.
- Skin and umbilical wound: omphalitis, pustular rashes, or abscesses.
- Vascular access: catheter-related bloodstream infections leading to phlebitis.
Early and late sepsis: what is the difference?
The disease is fundamentally divided into two forms depending on the time and conditions of infection.
Early-onset neonatal sepsis develops in the first days of life. Key risk factors are prematurity and premature rupture of membranes. The infant is infected intranatally (e.g., by aspirating amniotic fluid). Leading pathogens: Streptococcus agalactiae and Gram-negative flora, particularly Escherichia coli.
Late-onset neonatal sepsis is nosocomial in nature. Sources include incubators, catheters, formula feeds, or medical staff hands. The absolute leader among pathogens is Staphylococcus epidermidis; Staphylococcus aureus, Pseudomonas aeruginosa (Pseudomonas aeruginosa), and Klebsiella species are also common.
Clinical presentation variants
Depending on the rate of development of systemic inflammation, three clinical courses are distinguished:
- Fulminant (up to 7 days). Typical for early-onset sepsis in extremely low birth weight premature infants. Proceeds as septicemia (without purulent metastases). Septic shock develops with bradycardia, hypothermia, blood pressure drop, and oliguria. Prognosis is extremely grave.
- Acute (4–8 weeks). More common in late-onset sepsis. Manifests as septicopyemia—the formation of two or three purulent foci against the background of toxicosis. Characterized by thermoregulation disorders, gray-marbled skin, intestinal paresis, and respiratory distress. Mortality reaches 30–40%.
- Protracted (more than 8 weeks). Proceeds sluggishly, with blurred symptoms and a prolonged predominance of "minor" forms of infection. Trophic disorders, poor weight gain, hepatomegaly, and anemia come to the forefront. The most favorable variant with survival exceeding 70%.
Diagnostic workup
Bacteriological method is the gold standard. To confirm the diagnosis, the same pathogen must be isolated from at least two different sites (blood culture). However, the method is challenging: bacteremia is often transient (yield 20–60%), and asepsis violations can lead to sample contamination with skin flora.
When cultures are negative, laboratory markers are relied upon:
- Specific proteins and cytokines: elevated CRP, procalcitonin, interleukins (IL-6, IL-18), positive PCR.
- Complete blood count (CBC): leukocytosis, neutrophilia with a left shift, accelerated ESR, drop in hemoglobin and red blood cells.
- Biochemistry and urinalysis: elevated direct bilirubin, dysproteinemia, leukocyturia, and bacteriuria.
Principles of therapy
Treatment is carried out exclusively in the intensive care unit. The most important stage is nutritional support (priority given to breast milk or formulas with lactoflora to protect the intestine).
Initial antibiotic therapy is prescribed empirically intravenously, pending the antibiogram results:
- For early-onset sepsis, two drugs are combined (aminopenicillins, third-generation cephalosporins, aminoglycosides).
- For late-onset sepsis, guidance is based on the hospital's microbiological profile (most commonly carbapenems or third- to fourth-generation cephalosporins).
Concurrently, infusion therapy (correction of blood volume and DIC) and immunocorrection with immunoglobulin preparations enriched with the IgM fraction are performed.
To memorize the initial ports of entry of infection, use the mnemonic DRIP: Despiratory tract (pneumonia), Respiratory/GI (enterocolitis), Injections/catheters (phlebitis), Pumbral wound/Umbilicus (omphalitis).
Class and exam questions
How does sepsis clinically differ from generalized intrauterine infection (IUI)?
In sepsis, multiple organ dysfunction develops gradually, and the prognosis is relatively favorable (survival around 70%). In congenital intrauterine infection, which is more often viral in nature, MODS starts fulminantly, is accompanied by severe CNS damage, and mortality can reach 80%.
Why does exclusive parenteral nutrition negatively affect an infant with sepsis?
The absence of enteral nutrition leads to intestinal mucosal atrophy, a sharp decrease in protective secretory immunoglobulin A (sIgA) levels, and promotes colonization of the GI tract by pathogenic flora.
Is a single blood culture sufficient to rule out the diagnosis?
No. Due to the transient nature of bacteremia, the pathogen detection rate is no more than 20–60%. Repeat sampling from different sites is mandatory.
What else to study on this topic
- Pathogenesis and stages of DIC in newborns
- Principles of antibiogram interpretation and therapy adjustment
- Criteria for transferring a newborn to enteral nutrition
- Complications in surviving children: bronchopulmonary dysplasia and periventricular leukomalacia
- Mechanisms of catheter-related bloodstream infection (CRBSI) development
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