A 5-day-old preterm neonate (32 weeks gestation) with respiratory distress syndrome is on mechanical ventilation and develops clinical signs of late-onset neonatal sepsis (LONS). Regarding the microbiology and risk factors of LONS, all of the following statements are true EXCEPT:

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Accepted Answer

D. Group B Streptococcus (GBS) is a more common cause of LONS than early-onset sepsis. ## Late-Onset Neonatal Sepsis (LONS): Microbiology & Risk Factors ### Definition & Timeline **Key Point:** Late-onset sepsis occurs after 72 hours of life (typically >7 days). It differs fundamentally from early-onset sepsis (EOS) in causative organisms and risk factors. ### Microbiology Comparison: EOS vs LONS | Pathogen | EOS (0–72 hrs) | LONS (>72 hrs) | Comment | |---|---|---|---| | **GBS** | Most common (40–50%) | Less common (10–15%) | Vertical transmission; maternal colonization | | **E. coli** | Second most common (20–30%) | Moderate (10–20%) | Environmental acquisition | | **CoNS** | Rare (<5%) | Most common (30–40%) | Skin flora; catheter-associated | | **Candida** | Rare | Significant (5–15% in ELBW) | Fungal; prolonged antibiotics | | **Listeria** | ~5% | Rare (<1%) | Maternal transmission | | **Enterococci** | Uncommon | Common (10–15%) | Environmental | ### Why GBS Is NOT More Common in LONS **High-Yield:** GBS causes **early-onset sepsis** (vertical transmission from mother during labor/delivery). By definition, LONS occurs after 72 hours when maternal transmission is no longer the primary route. GBS accounts for only 10–15% of LONS, making it a minor pathogen in late-onset disease. **Clinical Pearl:** The shift from GBS (EOS) to CoNS and environmental organisms (LONS) reflects the transition from vertical to horizontal/environmental transmission. ### Risk Factors for LONS 1. **Prematurity** — especially <32 weeks 2. **Invasive devices** — central venous catheters, endotracheal tubes, umbilical lines 3. **Prolonged hospitalization** — >7 days 4. **Broad-spectrum antibiotics** — disrupts normal flora, selects resistant organisms and fungi 5. **Immunosuppression** — immaturity of neonatal immune system ### The Correct Answer Option 2 ("GBS is more common in LONS than EOS") is **false**. GBS is a hallmark of early-onset sepsis, not late-onset sepsis.

Answer

A. Prolonged hospitalization, invasive procedures, and broad-spectrum antibiotic exposure are major risk factors for LONS

Answer

B. Candida species are significant pathogens in LONS, especially in extremely low birth weight (ELBW) infants receiving prolonged antibiotics

Answer

C. Coagulase-negative staphylococci (CoNS) are the most common causative organisms in LONS, particularly in preterm infants with central lines

A 5-day-old preterm neonate (32 weeks gestation) with respiratory distress syndrome is on mechanical ventilation and develops clinical signs of late-onset neonatal sepsis (LONS). Regarding the microbiology and risk factors of LONS, all of the following statements are true EXCEPT:

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