A 5-day-old preterm neonate (28 weeks gestation) in the NICU develops clinical signs of sepsis. Blood culture and CSF culture are sent. Which is the most common site of infection in late-onset neonatal sepsis (LONS)?

Explanation

## Most Common Site of Infection in Late-Onset Neonatal Sepsis (LONS) **Key Point:** Bacteremia without a localized focus (primary septicemia) is the most common presentation of LONS, occurring in approximately 60–70% of cases. ### Sites of Infection in LONS | Site | Frequency (%) | Organisms | Risk Factors | |------|---------------|-----------|---------------| | Bloodstream (primary) | 60–70 | CoNS, S. aureus, Candida | Central lines, prolonged hospitalization | | Meningitis | 5–10 | GBS, E. coli, Listeria | Hematogenous spread from primary focus | | Urinary tract | 5–8 | E. coli, Klebsiella | Indwelling urinary catheter | | Skin/soft tissue | 3–5 | S. aureus, CoNS | Invasive procedures, poor skin care | | Pneumonia | 5–10 | Gram-negatives, Candida | Ventilator-associated | **High-Yield:** LONS (onset >72 hours of life) is predominantly **nosocomial** in origin, acquired from: - Central venous catheters (umbilical lines, PICC lines) - Endotracheal tubes - Urinary catheters - Environmental contamination - Healthcare worker hands ### Clinical Pearl Coagulase-negative Staphylococci (CoNS) are the most common organisms in LONS, particularly in preterm neonates with central lines. They cause: - Catheter-related bloodstream infection (CRBSI) - Primary bacteremia in 70% of cases - Meningitis in only 1–2% of cases (unlike GBS in EONS) **Mnemonic: LONS Organisms = "SCAM"** - **S**taphylococcus aureus - **C**oagulase-negative Staphylococci (CoNS) - **A**naerobes (rare) - **M**old/Candida (fungal, especially in preterm <1000g) ### Why Meningitis is Less Common in LONS Unlike EONS where meningitis occurs in 20–40% of E. coli cases, LONS meningitis is rare (5–10%) because: - CoNS and S. aureus have lower CNS tropism - Neonatal meninges are less permeable to these organisms - Hematogenous seeding is less frequent from catheter-related infections **Warning:** Do NOT assume meningitis is the most common site just because it is a feared complication. Always perform LP in suspected LONS, but bacteremia without CNS involvement is far more common. [cite:Nelson Textbook of Pediatrics 21e Ch 121]