Perinatal Infection

Although infections can occur in utero, birth represents a move from a highly protected environment to exposure to a vast array of new and potentially infectious agents. Especially in the latter part of pregnancy, maternal antibody in the form of IgG crosses the placenta to give the baby some protection in early life. This process will be less complete in the premature baby, especially if markedly premature. The T-lymphocyte system is also immature in the newborn, and even more so if premature.

Neonatal infections may be classified as early if they occur within the first 6 days of life and late if they occur within 7 to 90 days of life. Of early onset sepsis, 85% presents in the first 24 hours, 5% between 24 and 48 hours, and the other 10% over the next 4 days.

Early onset presentation may result from transplacental infection or infection from the mother's genital tract, especially if there was prolonged or early rupture of membranes.

Skin infections with Staphylococcus aureus are common. Peri-umbilical skin infections present a special risk because of the possibility of bacteria passing up the umbilical vein, causing thrombophlebitis and even a hepatic abscess. Infection appears as:

• Pustules, appearing either singly or in multiples without associated redness almost anywhere on the skin. They can cause a problem in the axillae or groin but rarely spread. They should be treated with antiseptic powder to prevent cross-infection.
• Bullous impetigo is less common but potentially far more serious. This presents as large pus-filled blisters that burst to form scabs. Where large areas of skin are involved, the condition is known as scalded skin syndrome. Treatment is with flucloxacillin, IV if necessary, and fluid replacement.
• Paronychia is infection of the nail fold and often involves more than one finger. It may produce pus. Treatment is with an antistaphylococcal cream.
• Acute mastitis is strictly an infection of subcutaneous tissue presenting with swelling, inflammation and fever. Treatment is with flucloxacillin and drainage of the abscess if needed.

An increasing problem in hospitals, is staphylococci that are resistant to methicillin and flucloxacillin. The public is familiar with the abbreviation MRSA. MRSA is rare in the community but not uncommon in hospitals, although stringent steps are being taken to eliminate it. The antibiotic of choice is usually vancomycin if parenteral treatment is required but for topical therapy fusidic acid and mupirocin should both suffice.

Simple infective conjunctivitis is often caused by S. aureus, streptococci or E. coli. Swabs should be taken for culture before treatment with chloramphenicol ointment. Infections that fail to respond fully may be caused by Chlamydia trachomatis passed on from the mother during delivery. Treatment is with tetracycline ointment or oral erythromycin.¹ Occasionally infection is complicated by dacrocystitis with inflamed swelling between the eye and the nose. Pressing this causes small amount of pus to appear on the lower eyelid. Treatment is a combination of massaging out the pus in this way and use of chloramphenicol ointment and oral flucloxacillin.

Ophthalmia neonatorum is caused by infection with N. gonorrhoea acquired from the mother and is potentially sight-threatening. It presents with a purulent conjunctivitis and is diagnosed by microscopy of pus. Treatment is with frequent chloramphenicol drops plus IM benzylpenicillin. It is a notifiable disease.

Candida albicans is a common commensal, but infection may affect the tongue and the rest of the mouth. It can spread to the GI tract causing diarrhoea and vomiting. It presents as a large number of firmly adherent, small, white plaques that may interfere with feeding by making the mouth sore. If the lesions are scraped with a tongue spatula, they will readily shift if they are only milk curds but thrush will be adherent. Treatment is with a topical antifungal such as nystatin suspension.

The incidence of serious acute infections in neonates is around 2 per 1,000 live births but the figure rises to 8 to 9 per 1,000 in small babies weighing just 1,000 to 2,000 grams and 26 per 1,000 in those of less than 1,000 grams. As mentioned above, this is in keeping with the immature immune system and the poor transference of maternal IgG in premature babies.

Diagnosis is complicated by the lack of clear clinical features of infection and very poor localising features. The lack of an effective immune response in the neonate means that infection can spread rapidly causing significant damage to organs.

Signs and symptoms are often non-specific and investigation for possible infection should be started on minimum suspicion as early treatment is essential. The following are suggestive of infection:

These should include:

• FBC. White count is very non-specific and platelets are often low in infection.
• Blood culture from peripheral vein
• Urine culture
• Ear, nose and throat swabs
• Swabs from any obvious sites of infection
• Lumbar puncture should be used quite readily
• Chest X-ray with respiratory signs
• U&Es
• Blood gases

Meningitis may cause any or all of these features but, in addition, convulsions and reduced level of consciousness are often seen. Congenital abnormalities, including metabolic abnormalities or abnormalities of the cardiovascular and respiratory systems may present in a manner similar to infection whilst infection may upset metabolic parameters, including blood gases, and cause impairment of cardio-respiratory function.

In early life, the commonest organisms are E. coli and group B β-haemolytic streptococci whilst after a few weeks the main organism is coagulase-negative staphylococcus (frequently methicillin-resistant). Blind treatment is with a penicillin plus gentamicin or cefotaxime/cefuroxime. Vancomycin plus gentamicin is used in late-onset sepsis if MRSA is found or suspected.

The signs of meningitis in an older child or adult are not present in a small infant. There may possibly be a bulging fontanelle but this is unreliable and such features as Kernig's sign and neck stiffness are of no value. There may possibly be depression of consciousness or convulsions. If there is any doubt a lumbar puncture should be performed as failure to treat meningitis has such serious consequences. The implicated organisms are totally different in the neonate from older patients. Group B haemolytic streptococcus and E coli are responsible for around two thirds of cases.

Pneumonia may be acquired through aspiration of the microorganisms during the delivery process. Infection causes pulmonary changes with infiltration, and destruction of bronchopulmonary tissue. Fibrinous exudation into the alveoli leads to inhibition of pulmonary surfactant function and respiratory failure with a presentation very similar to respiratory distress syndrome. Differentiating RDS from infection in a premature baby can be very difficult. Even segmental or lobar atelectasis, seen on chest x-ray, may occur in both.

Symptoms are similar to the non-specific ones of serious acute infections, including feeding difficulties and vomiting with fever and jaundice as variably present. Diagnosis is by examination of a urine sample, if necessary obtained by suprapubic bladder aspiration. Treatment should start immediately in the ill child, purely on clinical suspicion. Use IV cefotaxime or an aminoglycoside with careful monitoring of blood levels. After successful treatment, the urinary tract should be checked for congenital abnormalities.

Symptoms of diarrhoea and vomiting can cause dehydration and electrolyte disturbance. The infant is isolated and treatment is rehydration. If this cannot be achieved by the oral route, intravenous rehydration is required. Antibiotics are used only if there is suspicion of septicaemia.

Tuberculosis can be acquired from the mother very early in life and may present around 6 weeks of life with unwillingness to feed, excessive weight loss, slight fever and hepatosplenomegaly. Chest x-ray is required. Obtaining samples such as sputum is impractical in babies. Remember this possibility in those from high risk groups. Treatment is with standard anti-tuberculous drugs. As described in Immunisation And Immunisation Schedules, if there has been tuberculosis in the family in the past 6 months, BCG is given at 3 days.

HIV

Congenital HIV infection and its prevention is discussed elsewhere. Maternal HIV should be diagnosed before delivery that should be by LSCS to reduced the risk of infection of the infant and it is a contraindication to breast feeding.³ Neonatal infection presents within 24 months with opportunistic infections.

Hepatitis B or hepatitis C

The baby can acquire hepatitis B or hepatitis C infection from the mother but symptoms usually appear much later. If the mother is known to be HBsAg positive, hepatitis B vaccine is started at 3 days.⁴ There is no hepatitis C vaccine.

Herpes simplex

Herpes simplex infection is acquired from the mother during vaginal delivery and mainly infects the eye, skin or mouth. It can also cause a systemic infection producing meningo-encephalitis with jaundice and hepatosplenomegaly, and sometimes bleeding.⁵ Diagnosis is by viral culture and treatment is with IV aciclovir.

Congenital rubella

Infection is acquired early from the mother and can cause significant fetal damage in the first trimester. Infants remain infectious for a long time after delivery and need to be separated from those at risk of infection.

Coxsackie B

Coxsackie infection of type B appears as sporadic outbreaks in maternity unit with meningo-encephalitis and acute myocarditis. No treatment is available.⁶

Echovirus

Echovirus infection often presents with gastroenteritis but can affect any system with symptoms that range from slight illness to severe sepsis. Usually no treatment is required but immunoglobulins can be used in severe cases.

Serious neonatal infection has a bad prognostic implication for neuro-development and delay is common.⁷ This is especially so if the infant is premature. The inflammatory mediators may have an important role in neurotoxicity. There may also have been hypoxia. Oxygen therapy has to be monitored very carefully in infants, especially if premature as excessive oxygen can cause retrolental fibroplasia. Any baby that has received an aminoglycoside should have hearing assessed. Premature babies and their problems are discussed elsewhere.