Infants are exposed to a wide range of potential pathogens from the birth canal. The risk of infection is increased if there has been:
i) prolonged rupture of the membranes (especially if chorioamnionitis has developed)
ii) if the mother develops a fever
iii) if the infant is preterm
Presentation is usually non-specific. If systemic infection is suspected, investigation and treatment must be started promptly. A CXR is performed if there is respiratory distress, together with a septic screen comprising a FBC to detect neutropenia, blood cultures and urine and CSF for microscopy and culture. CRP is also measured in many centres. Antibiotics are started immediately without waiting for culture results. IV antibiotics are given to cover group B streptococci, Listeria monocytogenes and other Gram-positive organisms (usually penicillin or amoxicillin), combined with cover of Gram-negative organisms (an aminoglycoside). If cultures are negative and the infant has recovered clinically, antibiotics can be stopped after 48h.
Neonatal meningitis, although uncommon, has a mortality of 20-50%, with 1/3 of survivors having serious sequelae. Presentation is the same as for other forms of neonatal sepsis. A bulging fontanelle and lying with the back hyperextended (opisthotonus) are late signs. If meningitis is thought likely, ampicillin or penicillin and a third-generation cephalosporin (e.g. cefotaxime) are given. Complications include cerebral abscess, ventriculitis, hydrocephalus, hearing loss and neurodevelopmental impairment.
Nosocomially acquired infections are an inherent risk in a neonatal unit or postnatal wall. All staff must adhere strictly to effective handwashing to prevent cross-infection. In intensive care, the other main sources of infection are indwelling catheters for parenteral nutrition or ABG sampling, tracheal tubes and invasive procedures which break the protective barrier of the skin. Infection of indwelling catheters usually develops after the 1st week of life. Coagulase-negative Staph epidermidis is the most common pathogen in this situation. Broad-spectrum antibiotics are used but should include flucloxacillin or vancomycin to cover the above.
Group B streptococcal infection:
- Up to 30% of pregnant women have faecal or vaginal carriage of group B streptococci. Up to 50% of the infants born to these mothers carry the organism on their skin but only 1% of them become ill.
- Early-onset disease typically presents on day 1-3 with pneumonia, septicaemia and occasionally meningitis. Mortality is up to 10%.
- Transmission from mother to infant occurs during delivery or by ascending infection shortly before birth.
- Late-onset disease, from 1 week to 3 months of age, is less common. It usually causes meningitis but may present with focal infections such asosteomyelitis or septic arthritis.
- Antibiotics can be given during labour to mothers whose infants are at increased risk of infection. They can be identified from maternal colonisation of group B Streptococcus on universal screening at 35-38 weeks’ gestation, as is practised widely in the USA. Alternatively, at-risk infants can be identified if risk factors are present such as pre-term delivery, intrapartum maternal fever >38°C, prolonged rupture of the membranes, chorioamnionitis or a previously affected infant.
Listeria monocytogenes infection:
- Perinatal and neonatal Listeria infection is uncommon but serious. It is transmitted to the mother in food, such as unpasteurised milk, soft cheeses andundercooked poultry.
- It can cause a mild, influenza-like illness in the mother, or there may be asymptomatic faecal and vaginal discharge.
- Infection in pregnancy may cause spontaneous abortion, preterm delivery or fetal infection. The fetus usually acquires infection transplacentally, but also by ascending infection from the genital tract or at delivery.
- A characteristic feature of Listeria infection, even in preterm infants, is meconium staining of the liquor, which is otherwise unusual at an early gestation. There may be placental abscesses from which the organism can be cultured.
- In early-onset disease, presentation is at delivery or within the first few hours of life with septicaemia and pneumonia, a widespread rash and meningitis. The mortality is 30%. In late-onset disease, presentation is at 1-8 weeks of age, most often with meningitis, and has a better prognosis.
- Sticky eyes are common in the neonatal period, starting on the 3rd or 4th day of life. Cleaning with saline or water is all that is required and the condition resolves spontaneously.
- A more troublesome discharge may be due to staphylococcal or streptococcal infection and can be treated with a topical antibiotic eye ointment, e.g.neomycin.
- Purulent discharge with swelling of the eyelids within the first 48h of life is most likely to be due to gonococcal infection. The discharge should be Gram-stained urgently as well as cultured and treatment started immediately. In countries such as the UK and US where penicillin resistance is a problem, a third-generation cephalosporin is given IV.
- Chlamydia trachomatis eye infection usually presents with a purulent discharge and swelling of the eyelids towards the end of the 1st week of life, but may also present shortly after birth. The organism can be identified with a monoclonal antibody test on the pus. Treatment is with topical tetracycline eye ointment and oral erythromycin, both for 2 weeks.
- Both gonococcal and chlamydial eye infections need to be treated vigorously to avoid damage to the eye. The mother and partner also need to be checked and treated.
- The umbilicus dries and separates during the first few days of life. If the skin surrounding the umbilicus becomes inflamed, systemic antibiotics are indicated.
- Sometimes the umbilicus continues to be sticky, as it is prevented from involuting by an umbilical granuloma. This can be removed by applying silver nitrate while protecting the surrounding skin.
- Neonatal HSV infection is uncommon. It is usually transmitted during passage through an infected birth canal or by ascending infection. Most infections are caused by HSV-2.
- The risk to an infant born to a mother with a primary genital infection is high, about 40%, while the risk from recurrent materrnal infection is <3%. In most infants who develop HSV infection, the condition is unexpected as the mother’s primary infection is asymptomatic or causes a non-specific illness.
- The infection is more common in preterm infants. Presentation is at any time up to 4 weeks of age, with localised herpetic lesions on the skin or eye, or with encephalitis or disseminated disease.
- If the mother is recognised as having primary disease or develops genital herpetic lesions at the time of delivery, elective caesarean section is indicated. Women with a history of recurrent vaginal infection can be delivered vaginally as the risk of neonatal infection is very low. Aciclovir can be given prophylactically to the baby during the at-risk period.
Hepatitis B infection:
- Infants of mothers who are Hep B surface-Ag positive should receive Hep B vaccination shortly after birth to prevent vertical transmission. The vaccination course needs to be completed during infancy and antibody response checked.
- Babies are at highest risk of becoming chronic carriers when their mothers are ‘e’ antigen-positive but have no ‘e’ antibodies. Infants of ‘e’ antigen-positive mothers should also be given passive immunisation with Hep B Ig within 24h of birth.