Early-Onset Neonatal Sepsis (EONNS)
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| eonns vs lonns |
Early-Onset Neonatal Sepsis refers to systemic infection occurring within the first 72 hours of life (some definitions extend up to 7 days in term neonates). It is a medical emergency characterized by a rapid progression from nonspecific signs to septic shock, multi-organ dysfunction, and death if not promptly treated.
The pathogenesis is primarily linked to vertical transmission of microorganisms from mother to infant, either intrauterine (transplacental hematogenous spread) or intrapartum (ascending infection from the genital tract during labor or delivery). Infection often develops after rupture of membranes, especially when prolonged (>18 hours), or in the setting of maternal fever, chorioamnionitis, or Group B Streptococcus (GBS) colonization.
Globally, EONNS remains a significant contributor to neonatal morbidity and mortality, particularly in low- and middle-income countries, where rates are higher due to limited access to intrapartum prophylaxis, delays in recognition, and suboptimal infection control during delivery. Mortality is highest in very low birth weight (VLBW) and preterm infants, where the immature immune system and compromised skin/mucosal barriers amplify vulnerability.
The microbiological profile varies by region. In high-income settings, GBS and Escherichia coli dominate, whereas in many developing countries, Gram-negative bacilli such as Klebsiella pneumoniae are increasingly prevalent. Importantly, EONNS often presents with respiratory distress, apnea, temperature instability, and lethargy, sometimes within minutes of birth.
Prompt diagnosis relies on high clinical suspicion, early blood cultures, and sepsis screening, followed by empiric antibiotic therapy (usually ampicillin plus gentamicin) while awaiting culture confirmation. Prevention strategies — especially maternal GBS screening and intrapartum antibiotic prophylaxis — have markedly reduced incidence in settings where implemented.
Late-Onset Neonatal Sepsis (LONNS)
Late-Onset Neonatal Sepsis refers to systemic infection occurring after 72 hours of life (or after 7 days in some term-based definitions) up to 28 days of age in term infants, and up to 44 weeks corrected gestational age in preterm infants. Unlike EONNS, its etiology is dominated by horizontal transmission of pathogens, often acquired in the hospital environment (nosocomial) or from community contacts after discharge.
LONNS frequently affects preterm and critically ill neonates in the neonatal intensive care unit (NICU), where prolonged hospitalization, mechanical ventilation, invasive procedures, and parenteral nutrition predispose to infection. Biofilm-forming organisms such as coagulase-negative staphylococci (CONS) exploit indwelling central venous catheters, while Gram-negative bacilli and fungi such as Candida spp. cause severe systemic illness, especially in extremely low birth weight (ELBW) infants.
Clinically, LONNS may have a more insidious onset than EONNS, often manifesting as apnea/bradycardia spells, feeding intolerance, abdominal distension, or subtle changes in behavior or perfusion. However, fulminant septic shock can occur, particularly in S. aureus, Klebsiella, or Pseudomonas infections. Meningitis is proportionally more common in LONNS due to delayed recognition and sustained bacteremia.
The microbial spectrum varies with hospital ecology, antibiotic use patterns, and infection control practices. In resource-limited settings, multidrug-resistant Gram-negative pathogens are a major concern, complicating empiric therapy. Common empiric regimens include vancomycin plus an aminoglycoside or ceftazidime/meropenem, tailored to local antibiograms.
Prevention of LONNS hinges on rigorous infection control measures: meticulous hand hygiene, bundle-based catheter care, minimizing unnecessary invasive devices, strict aseptic preparation of parenteral nutrition, and antimicrobial stewardship. While mortality in term infants is lower than in EONNS, LONNS remains a major cause of prolonged NICU stay, chronic lung disease, neurodevelopmental impairment, and death in preterm survivors.
Comparison Table – EONNS vs LONNS
| Feature | Early-Onset Neonatal Sepsis (EONNS) | Late-Onset Neonatal Sepsis (LONNS) |
|---|---|---|
| Definition | Sepsis occurring within ≤72 hours of birth (some use ≤7 days in term, ≤72h in preterm) | Sepsis occurring after 72 hours (some use >7 days in term, >72h in preterm) |
| Primary Source of Infection | Vertical transmission from mother (intrauterine or intrapartum) | Horizontal transmission from environment, caregivers, or nosocomial sources |
| Mode of Transmission | Ascending infection after rupture of membranes, transplacental spread, exposure during passage through birth canal | Direct contact with infected personnel, contaminated equipment, invasive procedures |
| Common Risk Factors | – Maternal chorioamnionitis- Prolonged rupture of membranes (>18 h)- Maternal fever during labor- Preterm birth- GBS colonization- Low Apgar score | – Prolonged NICU stay- Indwelling central lines- Mechanical ventilation- Total parenteral nutrition (TPN)- Surgery- Cross-infection in NICU |
| Typical Pathogens | Term: Group B Streptococcus (GBS), E. coli, Listeria monocytogenes, Klebsiella, EnterococcusPreterm/NICU: Gram-negative bacilli (GNB), GBS | Gram-positive: Coagulase-negative staphylococci (CONS), S. aureusGram-negative: Klebsiella, E. coli, Pseudomonas, EnterobacterFungal: Candida spp. (esp. in VLBW on TPN) |
| Clinical Presentation | Rapid onset within first hours–days: respiratory distress, apnea, temperature instability, poor perfusion, hypotension, lethargy, seizures | More indolent onset: apnea/bradycardia spells, feeding intolerance, abdominal distension, lethargy, temperature instability, sepsis signs |
| CSF Findings (if meningitis) | Often presents concurrently with sepsis; E. coli, GBS common | More frequent with CONS, S. aureus, Candida; may follow prolonged bacteremia |
| Diagnosis | Blood culture before antibiotics, CBC, CRP/PCT, chest X-ray, LP (if stable) | Same work-up; consider line cultures, urine culture (rare in EONNS but important in LONNS) |
| Empiric Antibiotics | Ampicillin + Gentamicin (covers GBS, Listeria, Gram-negatives) | Vancomycin (for MRSA/CONS) + Gentamicin or Ceftazidime/Meropenem (GNB coverage; local antibiogram guided) |
| Prognosis | High mortality & morbidity if not promptly treated; increased risk of neurodevelopmental impairment in survivors | Lower acute mortality in term babies but significant morbidity in preterm/VLBW; risk of prolonged hospitalization |
| Prevention | – Maternal GBS screening & intrapartum prophylaxis- Aseptic delivery- Prompt management of PROM & maternal infections | – Strict hand hygiene- Minimal handling- Limiting invasive procedures- Bundle care for central lines & ventilation |
Notes on Early & Late Onset Neonatal Sepsis
1. Definition
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Neonatal sepsis: Clinical syndrome of systemic illness accompanied by bacteremia in the first 28 days of life.
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EONNS: ≤72 hours (some guidelines use ≤7 days in term).
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LONNS: >72 hours (or >7 days in term) up to 28 days (in preterm, up to 44 weeks corrected age).
2. Pathophysiology
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EONNS:
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Infection is acquired intrauterine (transplacental hematogenous spread) or intrapartum (ascending infection from vagina after rupture of membranes).
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Pathogens invade amniotic fluid → fetus aspirates/swallow infected fluid → hematogenous spread.
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LONNS:
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Mainly nosocomial or community-acquired after birth.
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Immature neonatal immune system + invasive devices = high susceptibility.
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Biofilm-forming organisms (e.g., CONS) on catheters are key in pathogenesis.
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3. Risk Factors
EONNS:
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PROM >18 hrs
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Maternal fever during labor (>38°C)
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Chorioamnionitis
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GBS colonization without prophylaxis
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Preterm (<37 wks)
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Meconium-stained liquor
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Low Apgar (<6 at 5 min)
LONNS:
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Prolonged NICU stay
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Invasive devices: ET tubes, central lines
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Surgery, necrotizing enterocolitis
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Poor infection control
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Broad-spectrum antibiotic exposure
4. Microbiology
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EONNS (classic teaching):
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GBS (Streptococcus agalactiae) – most common in term
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E. coli – more common in preterm, high mortality
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Listeria monocytogenes – rare but important in unpasteurized dairy exposure
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Others: Klebsiella, Enterococcus
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LONNS:
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CONS – esp. in VLBW with catheters
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S. aureus (MRSA possible)
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Gram-negatives: Klebsiella, Pseudomonas, Acinetobacter
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Candida albicans / C. parapsilosis
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5. Clinical Features
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Non-specific signs — must have high suspicion.
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EONNS often presents with:
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Respiratory distress (pneumonia common)
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Apnea, cyanosis
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Poor feeding, lethargy
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Hypotension, poor perfusion
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Seizures
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LONNS:
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Feeding intolerance, abdominal distension
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Apnea/bradycardia spells
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Temperature instability
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Signs of meningitis or NEC
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6. Investigations
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Blood culture (gold standard)
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CBC: leukopenia/leukocytosis, thrombocytopenia
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CRP, procalcitonin (serial trends helpful)
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CSF analysis & culture (unless unstable)
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Chest X-ray if respiratory distress
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In LONNS: line tip cultures, urine cultures
7. Management
Empirical therapy:
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EONNS: Ampicillin + Gentamicin
(Cefotaxime can replace gentamicin if meningitis suspected & renal issues, but avoid routine use due to resistance) -
LONNS: Vancomycin + Aminoglycoside / Antipseudomonal β-lactam
(Meropenem in multi-drug resistant GNB suspicion; guided by antibiogram)
Supportive care:
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Maintain oxygenation & perfusion
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Correct hypoglycemia
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Treat coagulopathy
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Restrict fluid in shock
8. Prognosis
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EONNS mortality: 5–50% (higher in preterm, GNB infections)
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LONNS: Mortality lower in term, but significant in VLBW; survivors risk bronchopulmonary dysplasia, neurodevelopmental delay.
9. Prevention
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EONNS: Maternal GBS screening (35–37 weeks), intrapartum antibiotics, clean delivery, timely rupture-to-delivery interval.
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LONNS: Hand hygiene, equipment sterilization, catheter bundles, antimicrobial stewardship.
