Group B Streptococcal Disease in Neonates Michael Addidle Clinical Microbiologist

Neonatal Group B Infection Bi-modal distribution Early onset – First 7 days, mean 12 hrs Late onset- 7days to 3 months, mean 3 weeks. Higher attack rates in premature babies 50% of babies born to colonised mothers acquire the organism. 1-2% of those will become ill from it.

Early Onset Group B Strep Disease Approx 1-2 per 1000 births Septicaemia 80% Pneumonia 10% Meningitis 10% Mortality 5-10%, inversely proportional to birthweight. Irritability, lethargy, tachypnoea, grunting, hypoxia, temp. instability, hypotension and poor perfusion. Fever is uncommon in first 24 hrs. WCC may be low, normal or high

Strategies to prevent Early Onset neonatal Group B Streptococcus Infection Universal based screening strategy. (US policy) Screen all pregnant women at 35-37 weeks gestation with a recto-vaginal swab, then giving all those positive for Group B Streps intra-partum antibiotics. Risk factor based approach. (UK and NZ policy) Previous infant with GBS disease GBS bacteriuria during this pregnancy Pre-term labour <37 weeks Prolonged rupture of membranes (>18hrs) Intra-partum fever >38C Funding and lack of evidence Compliance

Intra-partum antibiotics Note that antenatal antibiotics not shown to have benefit for vaginal colonisation with Group B streptococci. 1.2g IV Benzyl penicillin initially and then 0.6g 4 hrly during labour. If penicillin allergic (and no history of anaphylaxis), cephazolin 2g initially then 1g 8hrly If prior anaphylactic reaction to penicillin the either vancomycin 1g 12 hrly, or clindamycin 600mg 8hrly are indicated. (NZ guidelines recommend vancomycin but clindamycin is fine if Gp B strep isolated and known to be susceptible.) This will decrease incidence of invasive disease in newborn by approx 90%, most effective if abx started more than 4 hrs before delivery. If maternal chorio-amnionitis (intra-partum fever with two of the following signs: foetal tachycardia, uterine tenderness, offensive vaginal discharge or increased maternal WCC) then penicillin alone is insufficient. Broad spectrum abx required eg Amoxycillin clavulanate

Strategies to prevent neonatal Group B Streptococcus Infection Incidence of Group B neonatal disease slightly lower in screening based approach (0.33 v 0.59 per 1000 live births respectively) No discernible effect on mortality UK (and NZ) believe that screening approach is not cost-effective.

Strategies to prevent neonatal Group B Streptococcus Infection in New Zealand Grimwood K, Darlow BA, Gosling IA, et al. Early-onset neonatal group B streptococcal infections in New Zealand, 1998-1999. J Paediatr Child Health. 2002;38:272–7. 0.5 cases per 1000 live births. 60% of these cases had risk factors but had not received intra-partum antibiotics. Journal of the New Zealand Medical Association, 20-August-2004, Vol 117 No 1200 The prevention of early-onset neonatal group B streptococcus infection: technical report from the New Zealand GBS Consensus Working Party.

Downside of GBS prevention strategies Risk of serious anaphylactic reaction to penicillin is 1 in 10,000 and of a fatal reaction 1 in 100,000. Increased resistance to Group B streptococci. Anecdotal evidence for lincosamides in particular. Theoretical possibility of increased non-GBS infection eg E.coli has not been backed up by the majority of evidence however.

Summary Neonatal Group B streptococcal disease remains an important cause of morbidity and mortality. No strategy will prevent all early-onset neonatal GBS disease. Compliance is key to a risk factor based approach. Regular audit of above is recommended to ensure compliance. Audit of the 5 main risk factors is straightforward. Recognition of the signs of sepsis and early treatment of affected babies is just as important. Questions?