Can you provide an overview of neonatal sepsis, including its definition, classification (early‑onset ≤72 hours and late‑onset >72 hours), risk factors, clinical signs, diagnostic workup, and recommended management?

Neonatal Sepsis Overview

Neonatal sepsis is a life-threatening bloodstream infection occurring in the first 28 days of life, accounting for approximately 22% of global neonatal deaths, with mortality rates of 11-19% in high-income countries and substantially higher in low- and middle-income countries. 1

Definition and Classification

Neonatal sepsis is categorized by timing of onset:

• Early-Onset Sepsis (EOS): Occurs within 72 hours of birth (some definitions extend to 7 days)

  • Traditionally acquired peripartum from maternal genital tract
  • Classic pathogens: Group B Streptococcus and enteric Gram-negative bacteria (E. coli, Klebsiella)
  • However, this distinction is increasingly blurred, particularly in LMICs where Gram-negative and hospital-associated infections predominate even in EOS 1

• Late-Onset Sepsis (LOS): Occurs after 72 hours up to 28 days of life

  • Typically hospital-acquired pathogens
  • Strong risk factors: very low birth weight, early gestational age
  • Coagulase-negative staphylococci historically most common, but Gram-negative organisms now comprise 40-50% of cases 2, 3

Epidemiology and Burden

The global incidence is approximately 2,200 cases per 100,000 live births in high- and middle-income countries, equating to 3 million annual cases worldwide. Critically, the incidence in middle-income countries is up to 40 times higher than in high-income countries 1. An alarming trend shows 214,000 neonatal sepsis deaths annually are attributable to resistant pathogens 1.

Emerging Pathogen Trends

A concerning resurgence of Gram-negative organisms is occurring globally, with Gram-negative bacteria now accounting for 60% of neonatal sepsis in LLMICs 1. Recent data shows E. coli-related EOS increased 173% in late preterm/term neonates and 10% in very low birth weight infants between 2004-2013 and 2014-2024 3. This shift is accompanied by alarming rates of multidrug resistance, particularly against WHO-recommended empirical antibiotics 1.

Risk Factors

Maternal Risk Factors:

• Prolonged rupture of membranes (>18 hours)
• Maternal fever/chorioamnionitis
• Group B Streptococcus colonization
• Urinary tract infection
• Multiple vaginal examinations

Neonatal Risk Factors:

• Prematurity (especially <28 weeks gestation)
• Very low birth weight (<1500g)
• Male sex
• Invasive procedures (central lines, mechanical ventilation)
• Prolonged hospitalization
• Total parenteral nutrition

Clinical Recognition

Shock should be clinically diagnosed BEFORE hypotension occurs 4. The American College of Critical Care Medicine emphasizes early recognition using clinical examination rather than biochemical tests, though this remains debated 4.

Key Clinical Signs:

Temperature instability:

• Hypothermia or hyperthermia

Cardiovascular signs:

• Altered mental status
• Peripheral vasodilation (warm shock) OR vasoconstriction with capillary refill >2 seconds (cold shock)
• Threshold heart rates associated with increased mortality:
  • Infants: <90 bpm or >160 bpm
  • Children: <70 bpm or >150 bpm 4

Progressive hemodynamic deterioration predicts mortality:

• Eucardia (1% mortality) < tachycardia/bradycardia (3%) < hypotension with capillary refill <3 seconds (5%) < normotension with capillary refill >3 seconds (7%) < hypotension with capillary refill >3 seconds (33% mortality) 4

Other manifestations:

• Respiratory distress (apnea, tachypnea, grunting)
• Poor feeding, lethargy
• Abdominal distension
• Jaundice
• Seizures

Diagnostic Workup

Blood culture remains the gold standard for definitive diagnosis, though "culture-negative" sepsis varies widely worldwide 5.

Essential Laboratory Tests:

• Blood culture (before antibiotics when possible)
• Complete blood count with differential
• C-reactive protein (CRP)
• Procalcitonin (emerging biomarker)
• Blood gas analysis
• Lumbar puncture if clinically stable (for suspected meningitis)

Adjunct Monitoring:

• Serum lactate (controversial in neonates; recommended in adult sepsis bundles but not universally adopted for neonatal diagnosis) 4
• Troponin (correlates with poor cardiac function and inotropic response) 4

Risk Assessment Tools:

The sepsis calculator has become useful for managing early-onset sepsis in term infants, though similar tools do not exist for preterm infants or late-onset sepsis 2.

Management Strategies

Hemodynamic Support

Emergency department therapies should target restoration of:

• Normal mental status
• Threshold heart rates (as above)
• Peripheral perfusion (capillary refill <3 seconds)
• Palpable distal pulses
• Normal blood pressure for age 4

Reversal of hemodynamic abnormalities using ACCM/PALS recommended therapy was associated with 40% reduction in mortality odds ratio regardless of presentation stage 4.

Special Considerations for Preterm Infants

Very low birth weight infants (<30 weeks gestation) require a more graded approach to volume resuscitation and vasopressor therapy due to:

• Risk of intraventricular hemorrhage with rapid blood pressure shifts
• Concern for periventricular leukomalacia from prolonged underperfusion
• Patent ductus arteriosus persistence (rapid fluid administration may increase left-to-right shunting causing pulmonary edema) 4

One randomized controlled trial showed improved outcomes with daily 6-hour pentoxifylline infusions in very premature infants with sepsis, though this requires multicenter validation 4.

Antibiotic Therapy: Critical Gap in Current Recommendations

The WHO empirical antibiotic recommendations (gentamicin with ampicillin or benzylpenicillin as first-line; ceftriaxone as second-line) are likely inadequate in many LLMICs due to high rates of resistance against these antibiotics in Gram-negative bacteria 1. Analysis of 10,458 Gram-negative isolates from 88 studies across 19 LLMICs revealed:

• 60% of neonatal sepsis is Gram-negative
• High resistance rates to WHO-recommended empirical antibiotics
• Regional variations in bacterial types and resistance patterns 1

Clinical Implications:

Antibiotic selection must be guided by local antimicrobial resistance surveillance data and regional antibiogram patterns 1. In the absence of local data, clinicians should maintain high suspicion for treatment failure with standard regimens and have low threshold for escalation to broader-spectrum antibiotics while awaiting culture results.

Common Pitfalls:

• Delaying antibiotic therapy while awaiting diagnostic confirmation (mortality increases with delayed treatment)
• Using WHO recommendations without considering local resistance patterns
• Inadequate antibiotic stewardship leading to further resistance
• Under-recognition of sepsis in preterm infants with subtle presentations
• Over-reliance on biochemical markers rather than clinical assessment for initial diagnosis

Key Takeaways for Practice

1. Recognize sepsis clinically before hypotension develops - focus on perfusion, mental status, and heart rate thresholds
2. Gram-negative organisms are resurgent - E. coli and Klebsiella now dominate in many regions
3. Standard WHO antibiotic recommendations may be inadequate - know your local resistance patterns
4. Preterm infants need cautious fluid resuscitation - balance perfusion needs against hemorrhage risk
5. Blood culture remains essential - obtain before antibiotics when feasible
6. Early aggressive hemodynamic support reduces mortality by 40% - don't wait for laboratory confirmation