Neonatal Sepsis

Neonatal sepsis is a clinical syndrome of systemic illness in the first 28 days of life accompanied by bacteraemia. It remains a leading cause of neonatal mortality in India, and NEET PG loves it for vignettes that hinge on timing of onset, organism, and empirical antibiotic choice. Master the early- versus late-onset split and you have already answered most questions.

Definition & Classification

Neonatal sepsis = a clinical syndrome characterised by signs/symptoms of infection with or without accompanying bacteraemia in the first month of life. When a pathogen is isolated from a normally sterile site (blood, CSF, urine), it is culture-proven (confirmed) sepsis; when the clinical picture and sepsis screen are positive but cultures are sterile, it is clinical (probable) sepsis.

The single most examined classification is by age at onset:

Feature	Early-onset sepsis (EOS)	Late-onset sepsis (LOS)
Time of onset	≤72 h (classically ≤7 days; WHO ≤72 h)	>72 h to 28 days (and beyond in NICU)
Source / mode	Vertical — maternal genital tract, ascending or intrapartum	Horizontal — hospital (nosocomial), community, caregivers, equipment
Typical organisms (West)	GBS, E. coli, Listeria	Coagulase-negative Staph (CoNS), S. aureus, Klebsiella, Pseudomonas, Candida
Typical organisms (India)	Klebsiella, E. coli, Acinetobacter, S. aureus	Klebsiella, Acinetobacter, CoNS, Candida
Presentation	Pneumonia, fulminant multisystem, shock	Meningitis, focal infection, septic arthritis, UTI
Mortality	Higher, rapid	Lower but more meningitis

High-yield: In the West, the classic EOS triad is Group B Streptococcus (GBS), E. coli, and Listeria monocytogenes. In India (NNPD/DeNIS data), Gram-negative organisms — especially Klebsiella pneumoniae*, Acinetobacter, and *E. coli — dominate both EOS and LOS. Read the question stem's geography.

A third practical category is VLBW/NICU-acquired sepsis, dominated by CoNS (from central lines) and Candida.

Etiology & Risk Factors

EOS reflects vertical transmission; LOS reflects environmental acquisition and breaches of host defence (lines, ventilation).

Maternal/perinatal risk factors for EOS (mnemonic — the "5 P's of perinatal sepsis"):

1. Prolonged rupture of membranes — PROM ≥18 hours (a hard cut-off worth memorising).
2. Pyrexia — maternal intrapartum fever ≥38°C / clinical chorioamnionitis.
3. Preterm/low birth weight — the single strongest risk factor overall.
4. Positive GBS colonisation / GBS bacteriuria / previous GBS-affected baby.
5. Putrid/foul-smelling liquor (chorioamnionitis), and >3 unclean vaginal examinations during labour.

Additional Indian-relevant factors: home delivery in unhygienic conditions, dai handling, application of unsterile substances to the cord.

High-yield: Listeria causes a characteristic "granulomatosis infantiseptica" — disseminated micro-abscesses/granulomas (skin, liver, placenta) — and is associated with maternal consumption of unpasteurised dairy/soft cheese. It is one of the few organisms covered by ampicillin (cephalosporins do NOT cover Listeria).

Risk factors for LOS: prematurity/VLBW, central venous catheters, prolonged mechanical ventilation, prolonged TPN/parenteral nutrition, prior broad-spectrum antibiotics (selects for Candida and resistant Gram-negatives), prolonged NICU stay, and lack of breast feeding.

Pathophysiology

The neonate is functionally immunocompromised:

• Immature innate immunity — reduced neutrophil storage pool, impaired chemotaxis and opsonisation, low complement.
• Low transplacental IgG in preterms (most maternal IgG crosses in the third trimester) and absent IgM/IgA.
• Thin skin, immature gut barrier, indwelling devices providing portals of entry.

Bacteraemia → release of endotoxin/exotoxin → cytokine storm (TNF-α, IL-1, IL-6) → capillary leak, myocardial depression, microvascular thrombosis → septic shock, DIC, and multi-organ dysfunction. Because of immature blood–brain barrier and poor containment, meningitis frequently coexists (especially LOS) — hence the rule below.

High-yield: Always do a lumbar puncture in any neonate with suspected sepsis who is being worked up (especially LOS, positive blood culture, or any neurological sign). Up to 20–30% of culture-proven sepsis has concomitant meningitis that blood culture alone misses, and it changes antibiotic dose/duration.

Clinical Features

Signs are non-specific — "the baby is just not doing well." A change in feeding, activity, or temperature is often the earliest clue.

• General: lethargy, refusal to feed, "not looking well," temperature instability (hypothermia is more common than fever in neonates/preterms).
• Respiratory: apnoea, tachypnoea, grunting, retractions, cyanosis — EOS often presents as pneumonia/respiratory distress.
• Cardiovascular: tachycardia, poor perfusion, prolonged capillary refill (>3 s), hypotension (a late sign in neonates).
• GI: abdominal distension, vomiting, feed intolerance, ileus; in preterms watch for necrotising enterocolitis (NEC).
• CNS: lethargy/irritability, seizures, bulging fontanelle, high-pitched cry, hypotonia.
• Haematological/skin: jaundice (sepsis is a cause of pathological jaundice), petechiae/bleeding (DIC), sclerema, poor weight gain.

High-yield: Hypothermia + sclerema + poor activity in a neonate is sepsis until proven otherwise — do NOT wait for fever. Apnoea in a previously stable term baby is also a red flag for sepsis.

Diagnosis & Investigation

Blood culture is the gold standard, but it is slow and often falsely negative; the sepsis screen guides early decisions.

Investigation of choice

• Gold standard / confirmatory: Blood culture — ideally 1 mL from a peripheral vein before antibiotics; positivity usually within 48–72 h.
• Investigation of choice for meningitis: CSF analysis (lumbar puncture).
• Best single acute-phase reactant tracked serially: CRP (rises by 6–12 h, peaks 2–3 days). A normal CRP repeated at 24–48 h has high negative predictive value and supports stopping antibiotics.
• Procalcitonin — rises earlier than CRP (within hours) but has a physiological surge in the first 48 h of life.

Sepsis screen (Indian NNF criteria)

Component	Abnormal value (suggests sepsis)
Total leucocyte count (TLC)	<5,000/mm³ (leucopenia more ominous than leucocytosis)
Absolute neutrophil count (ANC)	Low per Manroe (term) / Mouzinho (VLBW) charts
Immature-to-total neutrophil ratio (I:T)	≥0.2
Band count / immature cells	Raised
Micro-ESR	>15 mm in first hour (or > age in days + 3)
CRP	>10 mg/L (>1 mg/dL)
Platelets	<1,00,000/mm³ (thrombocytopenia)

Interpretation: the screen is considered positive if ≥2 parameters are abnormal. It is most useful for its high negative predictive value — a negative screen lets you withhold/stop antibiotics in a well baby.

High-yield: The I:T (immature-to-total neutrophil) ratio ≥0.2 is the most sensitive single haematological marker in the sepsis screen and is heavily tested. Neutropenia carries worse prognosis than neutrophilia in neonatal sepsis.

Other workup: chest X-ray (if respiratory signs), urine culture by suprapubic aspiration or catheter (NOT bag — bag contaminates) for LOS/UTI, and surface/gastric aspirate cultures only have limited value.

Diagnostic flow (suspected EOS):

Risk factors / clinical signs → sepsis screen + blood culture (± LP) → start empirical antibiotics → reassess at 48–72 h with culture + repeat CRP → de-escalate / stop if culture negative & baby well, or tailor to sensitivity if positive.

Management / Drug of Choice

Two principles: empirical broad-spectrum cover started immediately after cultures, then de-escalation by sensitivity. Choice depends on EOS vs LOS and local antibiogram.

Setting	First-line empirical regimen (NNF/standard)
EOS (community/labour-room)	Ampicillin (or penicillin) + an aminoglycoside (gentamicin/amikacin)
LOS / hospital-acquired	Depends on unit flora; commonly a β-lactam + aminoglycoside, escalating to piperacillin-tazobactam / cefotaxime ± aminoglycoside; vancomycin if CoNS/MRSA/line sepsis suspected
Meningitis	Add/switch to cefotaxime (good CSF penetration) + ampicillin; avoid ceftriaxone in neonates (displaces bilirubin → kernicterus; calcium precipitation)
Listeria cover	Ampicillin (+ gentamicin synergy)
Suspected fungal (Candida)	Amphotericin B (deoxycholate) is the agent of choice in neonates; fluconazole for prophylaxis

High-yield: Cefotaxime — NOT ceftriaxone — is the cephalosporin of choice in neonates. Ceftriaxone is avoided because it displaces bilirubin from albumin (kernicterus risk) and forms calcium-ceftriaxone precipitates (fatal in neonates receiving calcium-containing fluids).

High-yield: Aminoglycosides are first-line empiric partners, but the drug of choice for confirmed Pseudomonas is an antipseudomonal agent — piperacillin-tazobactam, ceftazidime, or cefepime ± aminoglycoside.

Duration: culture-proven sepsis without meningitis — 10–14 days; meningitis — Gram-positive 14 days, Gram-negative 21 days; clinical sepsis with negative culture but positive screen — usually 7–10 days. Stop at 48–72 h if culture negative, screen negative, and baby asymptomatic.

Supportive care (often the deciding factor in survival): thermoneutral environment, oxygen/respiratory support, fluids and inotropes (dopamine/dobutamine, adrenaline/noradrenaline for refractory shock) for septic shock, correction of hypoglycaemia and metabolic acidosis, fresh frozen plasma/platelets for DIC, and breast feeding/expressed breast milk which is protective.

Adjuncts (know the evidence): IVIG — not routinely recommended (INIS trial showed no mortality benefit). G-CSF/GM-CSF — only for documented severe neutropenia, not routine. Probiotics reduce NEC and LOS in preterms in some trials.

Prevention

• Intrapartum antibiotic prophylaxis (IAP) with intravenous penicillin G (or ampicillin) to GBS-colonised mothers (screen at 35–37 weeks) — the cornerstone that has slashed GBS EOS in the West.
• Hand hygiene (the single most effective NICU measure), aseptic line care, minimal/early removal of catheters, KMC (Kangaroo Mother Care) and exclusive breast feeding, antenatal care, clean delivery practices.

Complications

• Septic shock and multi-organ dysfunction — leading cause of death.
• Meningitis → hydrocephalus, ventriculitis, neurodevelopmental sequelae, hearing loss, seizures.
• DIC with bleeding.
• Necrotising enterocolitis (NEC) — pneumatosis intestinalis, bowel perforation.
• Persistent pulmonary hypertension (PPHN) complicating GBS pneumonia.
• Septic arthritis / osteomyelitis (especially S. aureus in LOS).
• SIADH, renal failure, cholestatic jaundice.
• Death — neonatal sepsis is among the top three causes of neonatal mortality in India.

Key Differentials

The non-specific presentation overlaps with many neonatal conditions; the screen and cultures discriminate.

• Respiratory distress causes: transient tachypnoea of the newborn (TTN), respiratory distress syndrome (RDS/HMD), meconium aspiration — vs sepsis-related pneumonia.
• Metabolic: hypoglycaemia, inborn errors of metabolism (presenting with lethargy/acidosis/poor feeding), hypocalcaemia.
• Cardiac: duct-dependent congenital heart disease presenting with shock/collapse around day 3–7 (do hyperoxia test; check femoral pulses).
• CNS: hypoxic-ischaemic encephalopathy, intracranial haemorrhage, neonatal seizures of other cause.
• GI: NEC vs sepsis with ileus; surgical abdomen.
• Haematological: isoimmune haemolysis / TORCH infections (CMV, toxoplasma, rubella, syphilis) presenting with jaundice, petechiae, hepatosplenomegaly — a classic mimic, so consider TORCH in EOS with growth restriction and rash.

Recently asked / exam angle

NEET PG and INI-CET have repeatedly tested:

• Most common organism causing neonatal sepsis in India → Klebsiella (Gram-negatives overall), contrasting with GBS in the West — the geography flip is the favourite trap.
• Cefotaxime over ceftriaxone in neonates — reason: bilirubin displacement (kernicterus) and calcium precipitation.
• PROM ≥18 h and maternal fever/chorioamnionitis as the key EOS risk factors.
• I:T ratio ≥0.2, micro-ESR >15 mm, and CRP values in the sepsis screen; "which is most sensitive" → I:T ratio; "neutropenia vs neutrophilia prognosis."
• Empirical regimen = ampicillin + gentamicin; Listeria covered by ampicillin not cephalosporins.
• IVIG not beneficial (INIS trial) — a frequent "true/false adjunct" MCQ.
• Vignette of maternal unpasteurised cheese + neonatal granulomatous skin lesions → Listeria (granulomatosis infantiseptica).
• Amphotericin B as antifungal of choice for neonatal candidiasis in VLBW with prolonged antibiotics/lines.
• GBS prophylaxis: screen at 35–37 weeks; intrapartum IV penicillin.

Rapid revision

1. EOS ≤72 h, vertical, pneumonia/shock; LOS >72 h, horizontal, meningitis.
2. West triad: GBS + E. coli + Listeria; India: Klebsiella/E. coli/Acinetobacter dominate.
3. PROM ≥18 h = key EOS risk; prematurity/VLBW is the strongest overall.
4. Hypothermia, not fever, is the common temperature sign in neonates.
5. Blood culture = gold standard; CRP best serial marker; I:T ratio ≥0.2 most sensitive screen item.
6. Sepsis screen positive if ≥2 of: TLC <5000, I:T ≥0.2, micro-ESR >15 mm, CRP >10 mg/L, low platelets.
7. Always consider LP — meningitis coexists in up to 30% of culture-proven sepsis.
8. Empirical EOS: ampicillin + gentamicin. Listeria → ampicillin (cephalosporins don't cover it).
9. Cefotaxime, not ceftriaxone, in neonates (kernicterus + calcium precipitation).
10. Pseudomonas → piperacillin-tazobactam/ceftazidime/cefepime; Candida → amphotericin B.
11. IVIG not routine (INIS trial); G-CSF only for documented neutropenia; breast feeding + hand hygiene + KMC are protective.
12. GBS prevention: screen at 35–37 weeks, give intrapartum IV penicillin; duration of therapy — sepsis 10–14 d, GN meningitis 21 d.