Prevention of Neonatal Group B Streptococcal Sepsis: Is Routine Antenatal Screening Appropriate
Authors: Gilbert Gwendolyn L. , Isaacs David , Burgess Margaret A. , Garland Suzanne M. , Grimwood Keith , Hogg Geoffrey G. , Mclntyre Peter 
Published: February 2008

EDITORIAL COMMENT: This position paper has a senior team of authors from Departments of Microbiology and Infectious Diseases, Oncology and Paediatrics and carries the weight of the Paediatric Infectious Diseases Group of the Australasian Society for Infectious Diseases. This impressed but did not intimidate the editorial subcommittee and other reviewers of this article, who although recommending publication, wish to ask readers to consider the following points. Firstly, the authors do not include an obstetrician, and obstetricians do not favour routine screening for group B streptococcal carriage by vaginal and rectal swabbing because women do not like rectal swabbing. The result of introduction of routine vaginal and rectal swabbing at 26‐28 weeks' gestation in the hospital where the editor works in an antenatal clinic was that the policy failed because of the rectal swabbing, with the result that vaginal swabs are now performed in less than 50% of patients attending the clinic, although it remains hospital policy for routine swabbing to be performed. Secondly, recommendations need to be dogmatic and precise if clinicians are to follow the favoured regimen. This paper has no clear statement of what constitutes ‘an epidemiological risk factor for infection’ in the women for whom intrapartum prophylaxis is recommended, nor is there a statement of the antibiotic regimens favoured. Moreover, there is no recommendation about antibiotic therapy for the infant. Our third concern is that the calculations in this paper and its tables are based on the assumption that the perinatal mortality rate from neonatal sepsis due to group B streptococcus is 20% of the 2 per 1,000 with neonatal sepsis due to this organism ‐ if. a death rate of 1 in 2,500 births.

Table A shows the number of perinatal deaths in Victoria, 1984–1993, in which group B haemolytic streptococcus was identified. The rate was 1 in 6,283 births for the 10‐year interval and 1 in 19,566 births for the 3 years, 1991‐1993. These data include cases in which the organism was cultured but death was considered to be due to other causes. The extent to which the recent reduction in deaths from group B streptococcus is a result of 1 or more of the recommendations in this paper is not known. It should be noted that at least one third of the perinatal deaths associated with group B streptococcus identification in Victoria were stillbirths and so unlikely to have been prevented by intrapartum antibiotic therapy indicated by a risk factor or positive antenatal culture.

Reply from Authors: We are aware that many obstetricians and patients find rectal swabbing unacceptable and that it is therefore not often done. Since the data suggest that rectal as well as vaginal swabbing is required for optimal predictive values for screening, this is a serious disadvantage of strategy A and one reason why its full implementation is difficult. Strategy C is given at least equal weight in our recommendations because we believe it is a suitable alternative for individual practitioners and institutions who find antenatal screening for GBS carriage unacceptable or impracticable.

We agree that protocols must be dogmatic, precise and simple but may vary (legitimately) in different settings. Our intention was to provide a framework for development of detailed protocols based on general strategies.

Since the focus of our paper is prophylaxis, we felt that recommendations for antibiotic therapy in the infant were not appropriate. There should be no need for routine antibiotic therapy in otherwise healthy infants at risk, if prophylaxis has been given correctly. Management of infants and indications for antibiotic therapy do not differ from those in other infants, depending on clinical findings.

Epidemiological factors associated with a higher risk of GBS sepsis should have been clearly defined. They are: previous GBS infected infants, twins and GBS bacteriuria.

Our estimate of the incidence and mortality from GBS sepsis is based on published local and overseas data which vary considerably but are derived from reviews of cases of GBS sepsis diagnosed (usually during life) on the basis of defined criteria. The apparent fall in the incidence of GBS‐related perinatal mortality in Victoria does not reduce the need for cost‐effective preventative strategies.

We agree that the fact that intrapartum antibiotic prophylaxis cannot prevent intrauterine infection and its complications (including stillbirth and preterm delivery) is a major limitation of any currently available strategies, as acknowledged in the manuscript. Immunization is likely to be the only way this risk may be reduced in future, but is unlikely to be available for many years.

Summary: Four strategies for prevention of early onset neonatal group B streptococcal (GBS) sepsis were considered:

A: routine antenatal screening for GBS vaginal carriage at 26–28 weeks' gestation and intrapartum antibiotic prophylaxis for all carriers;

B: screening as above and prophylaxis only for carriers with risk factors for sepsis;

C: prophylaxis for all women with risk factors;

D: as for C plus screening at 37 weeks' gestation and prophylaxis for carriers.

The outcomes considered for each option were: the proportion of women given prophylaxis; the risk of anaphylaxis; cases of neonatal GBS sepsis and deaths prevented; costs of screening, prophylaxis and of acute care of remaining cases. Published local and overseas studies of neonatal GBS sepsis, effectiveness of antenatal screening and prophylaxis and estimated costs were evaluated.

Any of the proposed strategies can prevent a significant proportion of cases of neonatal GBS sepsis and a strategy for prevention of neonatal group B streptococcal sepsis should be part of routine obstetric practice. Strategy C is simple, effective, inexpensive and avoids unnecessary antibiotic use; it is recommended particularly when antenatal care is provided mainly in community or private practice. Strategy A (using vaginal and rectal swabs for screening) could prevent more cases, but at greater cost which could be justified only if protocols can be properly implemented and monitored.