Conditions · Pediatrics and neonatology
Neonatal sepsis !
A serious bloodstream infection in a baby's first month. Signs can be vague, so it is treated fast whenever suspected.
Updated 2026-11-01
Structures involved
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Microorganisms that cause it
In embryology
In the clinical exam
Why it happens
- How septic shock develops
- Systemic effects of inflammation: fever, acute-phase proteins, leukocytosis, sepsis
- Necrotizing enterocolitis: why the premature gut is vulnerable
- Prematurity and fetal growth restriction
- Newborn physiology and fetal maturation
- Innate and adaptive immunity: overview
What it is
A systemic infection, usually bacterial, in an infant within the first 28 days of life, confirmed or suspected, that can involve the blood, lungs and meninges. It is divided into early onset (first 72 hours, or first week by some definitions) and late onset.
Who gets it
A major cause of neonatal death worldwide, with the heaviest burden in low- and middle-income countries. In Latin America, including Colombia, it is among the main causes of neonatal mortality and of antibiotic use in neonatal units, and very preterm and low-birth-weight infants carry the highest risk.
Causes
- Early onset: organisms from the maternal genital tract, mainly group B streptococcus and Escherichia coli; Listeria monocytogenes less often
- Late onset: hospital or community organisms, such as coagulase-negative staphylococci, Staphylococcus aureus, gram-negative bacilli and Candida
- Viral infections such as herpes simplex or enterovirus can mimic bacterial sepsis
Risk factors
- Maternal group B streptococcus colonisation without adequate intrapartum prophylaxis
- Prolonged rupture of membranes (18 hours or more)
- Maternal fever in labour or chorioamnionitis
- Prematurity and low birth weight
- Central lines, mechanical ventilation and prolonged hospital stay (late onset)
- Maternal urinary tract infection, previous infant with GBS disease
Pathophysiology
Organisms reach the fetus by ascending infection or during passage through the birth canal (early onset), or later from the environment, devices and caregivers' hands (late onset). The newborn's immature innate immunity, low immunoglobulin levels (especially in preterms) and thin skin let bacteria spread to the blood, lungs and meninges, triggering a systemic inflammatory response with poor perfusion and organ dysfunction.
Classification
- Early-onset sepsis: first 72 hours of life (some use the first 7 days), mostly vertical transmission
- Late-onset sepsis: after 72 hours to day 28 (or later in preterm infants still in hospital), mostly nosocomial or community acquired
Symptoms and signs
- Temperature instability: fever or, especially in preterms, hypothermia
- Poor feeding, lethargy or irritability, hypotonia
- Respiratory distress, apnoea or increased oxygen need
- Poor perfusion: pallor, mottling, prolonged capillary refill, tachycardia or bradycardia
- Vomiting, abdominal distension or feeding intolerance
- Jaundice or glucose instability (hypo- or hyperglycaemia)
Diagnosis
- Clinical
- Signs are non-specific, so suspicion is based on maternal risk factors plus any change in behaviour, feeding, breathing, temperature or perfusion; structured risk calculators or serial examinations guide who needs treatment.
- Tests
- Blood culture before antibiotics is the gold standard. Complete blood count (very low or high white cells, high immature-to-total neutrophil ratio, low platelets) and C-reactive protein or procalcitonin, ideally serial. Lumbar puncture for CSF analysis and culture; urine culture in late onset. Glucose, lactate and blood gases.
- Imaging
- Chest X-ray when there are respiratory signs; cranial ultrasound if meningitis is confirmed; abdominal X-ray if necrotising enterocolitis is suspected.
Differential diagnosis
- Neonatal respiratory distress syndrome or transient tachypnoea
- Congenital heart disease with low output (duct-dependent lesions)
- Inborn errors of metabolism
- Neonatal hypoglycaemia or hypothermia from other causes
- Congenital infections (TORCH) and neonatal herpes
Goal of treatment
Start effective antibiotics quickly after cultures, support breathing and circulation, find and treat the focus (especially meningitis), and stop antibiotics early when cultures are negative and the infant is well.
Treatment
- Medical
- Empirical intravenous antibiotics after cultures: for early onset, ampicillin plus an aminoglycoside is the classic combination (covers GBS, E. coli and Listeria); late-onset regimens add cover for staphylococci and resistant gram-negatives according to local data; adjusted once cultures return.
- Acute
- Supportive care: oxygen or ventilation, fluid boluses and vasoactive drugs for shock, correction of glucose, electrolytes and acidosis, and thermal support.
- Follow-up
- Nursing care: vital signs, temperature, perfusion, glucose and feeding tolerance; strict hand hygiene and central-line bundles to prevent late-onset infection; correct blood culture technique.
- Medical
- Antiviral therapy (acyclovir) when neonatal herpes is suspected; antifungals for invasive candidiasis.
Drugs for this condition
Complications
- Septic shock and multi-organ failure
- Meningitis with hydrocephalus, brain abscess, hearing loss or neurodevelopmental impairment
- Disseminated intravascular coagulation
- Death, highest in very preterm infants and gram-negative or fungal sepsis
Prognosis
Mortality has fallen with prompt treatment but remains significant, especially in preterm infants and in settings with limited intensive care; survivors of meningitis have a high rate of long-term neurological sequelae.
Prevention
- Universal antenatal screening for GBS (about 36–37 weeks) and intrapartum antibiotic prophylaxis for carriers
- Treatment of maternal chorioamnionitis and urinary infection
- Hand hygiene, central-line care and antibiotic stewardship in neonatal units
- Breast milk, especially colostrum, for preterm infants
Test yourself
Think of the answer, then tap the question to see it.
What are the two most common causes of early-onset neonatal sepsis?
Group B streptococcus and Escherichia coli.
What is the usual empirical antibiotic regimen for early-onset neonatal sepsis?
Ampicillin plus an aminoglycoside (such as gentamicin), covering GBS, E. coli and Listeria.
Which test is the gold standard for diagnosing neonatal sepsis?
Blood culture taken before antibiotics; CSF culture is added to rule out meningitis.
How is early-onset GBS disease prevented?
Antenatal GBS screening at about 36–37 weeks and intrapartum antibiotic prophylaxis for colonised mothers or those with risk factors.
Why may a septic preterm infant be hypothermic rather than febrile?
Immature thermoregulation; temperature instability, including hypothermia, is a classic sign of neonatal sepsis.
Related conditions
- Sepsis and septic shock
- Bacterial meningitis
- Prematurity and its complications
- Neonatal respiratory distress syndrome (hyaline membrane disease)
- Necrotising enterocolitis
- Urinary tract infection (acute cystitis)
- Neonatal hypoglycaemia (including infant of a diabetic mother)
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Neonatal sepsis (MedlinePlus (U.S. National Library of Medicine), 2024); Clinical Overview of Group B Strep Disease (Centers for Disease Control and Prevention (CDC), 2024).
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Representative model, for educational purposes only.
