Infection and Immunity

Maternal antibodies start transferring across to the fetus in the last trimester. When maternal antibody levels decline, infants can then become susceptible to viral infections.

– In addition to the normal vaccines, there are selective immunisation groups:

i) Hepatitis B –> gives to babies born to hep B infected mothers (3 shots)

ii) TB –> BCG vaccine is given to infants born in high-risk country or with parent from high-risk country. (1 shot) 

Neonatal Infections

Early Onset Infection

This describes an infection which occurs with an onset <72rs after birth

– The most common pathogen is Group B Streptococci, then E. Coli and Listeria

– The infection can originate in many sources, but the most common is an ascending infection from the birth tract

– Bacteria ascended from the birth canal and invaded the amniotic fluid

– The fetus is infected because the foetal lungs are in direct contact with infected amniotic fluid

– This leads to pneumonia and septicaemia

Risk factors:

– Prematurity, premature rupture of membranes, Chorioamnionitis

– IV antibiotics given to mother within 24 hours of delivery

– Infection in another baby if multiple pregnancies

Symptoms:

– Respiratory distress –> cyanosis, grunting, tachypnoea

– Shock

– Seizures

– Cyanosis and requiring mechanical ventilation

– Floppiness

– GI symptoms –> inability to feed, abdominal distension and vomiting

Management:

Start antibiotic treatment if any red flags or 2+ risk factors:

– Empirical antibiotics given before blood culture results –> IV benzylpenicillin + gentamicin

– If cultures + CRP are negative, and the infant is asymptomatic, antibiotics can be stopped after 36-48hrs 

Late Onset Infection

This describes an infection in neonates that occurs >72 hours after birth

– Unlike in early onset infection, the main source of infection is environmental (hospital or community)

– Most common is Coagulase-negative staphylococcus e.g., staph epidermidis

– Also due to community organisms S. Aureus and E. coli

Risk factors:

Prematurity, underlying cardio/respiratory disease, admission to NICU

Symptoms:

Similar to early onset infection

Tests:

Septic screen

Lumbar puncture

Management:

– 1st line –> empirical antibiotic treatment e.g., flucloxacillin and gentamicin

– If there is no improvement in symptoms –> can add antibiotics like vancomycin for coagulase-negative staphylococcus