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Prevention of early onset neonatal group B streptococcal infection

The Group B streptococcus (GBS) or Streptococcus agalactiae was first recognised as a major perinatal pathogen in the UK in the 1970s. Early onset Group B streptococcal (EOGBS) infection is now the commonest cause of neonatal sepsis in developed countries. Infants with group B streptococcal disease may present with sepsis, meningitis, or pneumonia. Group B streptococcus is a commensal of the gastrointestinal tract and vagina and can be recovered from 10–30% of pregnant women in the USA and the UK. Infection is acquired intrapartum and can be prevented by intrapartum antibiotic prophylaxis. Neonatal disease is either early onset or late onset, the former occurring within seven days of life. Late onset disease can also result from acquisition of the micro-organism in the hospital or community. In 1990 in the USA, the national incidence of EOGBS neonatal infection was estimated at 1.8 cases per 1000 live births resulting in 310 neonatal deaths. Maternal risk factors identified for neonatal GBS include spontaneous preterm onset of labour (<37 weeks gestation), prolonged rupture of membrane (>18 hours), maternal fever (>37.5oC) and a previous baby infected with GBS. 4 5 The incidence is highest in babies born preterm, and in the USA to young mothers (< 20 years), black and primiparous. Disease incidence in Australia is comparable with the USA in white Australians, but is even higher in Australian aboriginal babies. Despite a comparable level of maternal colonisation in the UK, the incidence of EOGBS infection is considered to be lower. However, there has been a marked lack of studies of the incidence and risk factors for EOGBS infection in the UK. The UK rate is quoted as 0.5–1.15 per 1000 live births. A major weakness of these published studies is that they have not included urban and deprived areas where the incidence may be expected to be higher. Significant eVorts have been expended in the USA to quantify and cost EOGBS infection, and in 1996 the Centers for Disease Control in Atlanta issued a document on prevention which was endorsed by the American College of Obstetricians and Gynaecologists and by the American Academy of Paediatricians. The guidelines proposed the use of one of two strategies to determine which women should receive intrapartum antibiotic prophylaxis (IAP). One strategy, based on rectal and vaginal cultures taken at 35–37 weeks of pregnancy recommends that IAP is given to all group B streptococcus carriers. In the other strategy, women are identified for treatment on the basis only of risk factors for neonatal sepsis with no pre-natal microbiological screening cultures. These recommendations were revised from early guidelines which were not agreed by paediatricians and obstetricians, and consequently were not widely implemented. The core recommendation in the 1996 document is the administration of intravenous penicillin G to women at the onset of labour to reduce the risk of neonatal EOGBS infection. Clindamycin is the alternative therapy for women allergic to penicillin. A recent review of the incidence of EOGBS disease during the 1990s in the USA has shown that there has been a decline by 65% from 1.7 to 0.6 cases per 1000 live births. Implementation of the recommended policies is considered a significant factor for the reduction in reported incidence. By 1999, approximately two thirds of hospitals and more than 90% of obstetricians in the USA had adopted these policies. After publication of the consensus guidelines in the USA, there was uncertainty as to whether such prevention strategies should be universally adopted in the UK especially in the light of the lack of information on disease incidence and risk factors. A number of ad hoc policies for prevention were developed in UK maternity units, some based on local surveillance studies and others based on the USA experience. In most units policies were not available. The Public Health Laboratory Service (PHLS) established a Group B Streptococcus Working Group in 1998. The membership includes a paediatrician, a neonatologist, an obstetrician, and a midwife, all nominated by the respective Royal Colleges, as well as microbiologists and public health specialists. There are also representatives of the Department of Health and the National Childbirth Trust. The remit of the Working Group is to measure incidence, risk factors, attributable morbidity and mortality, and the relevant economic data for early onset neonatal group B streptococcus infection in the UK and to formulate rational evidence based guidelines for prevention. In March 2001, a national surveillance study of neonatal group B streptococcal infection in the UK was completed. This study, through the PHLS and the British Paediatric Surveillance Unit (BPSU) was funded by the Meningitis Research Foundation (MRF). The Working Group has also initiated a case control study, also funded by MRF, to address risk factors and outcome. Data from these studies will go towards a health economics analysis which will identify the costs attributable to GBS in the UK and consider the costs of prevention using diVerent strategies. Carriage studies have been initiated in several UK hospitals, and an enhanced surveillance study of culture negative EOGBS in four major London hospitals is underway. Until evidence based guidelines can be produced, it is worthwhile considering in detail the potential implications of screening for prevention of EOGBS infection. Boyer and GotoV were the first to show that intrapartum antibiotics together with postpartum antibiotics for the neonate reduce or even prevent EOGBS infection. Subsequent meta-analysis of controlled trials has confirmed their findings with one study demonstrating a 30-fold reduction in GBS disease. Also, a systematic review published by the Cochrane Pregnancy and Childbirth Group concluded that “intrapartum antibiotic treatment of women colonised with Group B streptococcus appears to reduce neonatal infection”. However, the issue of which women should be selected for IAP is a diYcult one and two general J Med Screen 2001;8:170–172 170