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NEONATAL SOCIETY ABSTRACTS

Real time polymerase chain reaction for the rapid detection of group B streptococcus in colonised infants and maternal postnatal low vaginal swabs

Presented at the Neonatal Society 2009 Summer Meeting (programme).

Storey I1, Vickers A2, Efstratiou A2

1 Heart of England NHS Trust, Heartlands Hospital, Bordesley Green East, B9 5SS, UK
2 Health Protection Agency, Centre for Infections, 61 Colindale Avenue, London, NW9 5HT, UK

Aim: Group B Streptococcus (GBS) is the leading cause of neonatal sepsis. Rapid and effective identification of both colonised mothers and their babies in the immediate postnatal period would allow targeted treatment of infants at risk of GBS bacteraemia. It was hypothesised that the Polymerase Chain Reaction (PCR) would be able to identify postnatal mothers and babies colonised with GBS more rapidly and with a greater accuracy than conventional culture methods.

Methods: Subjects were recruited from a UK level 3 neonatal unit. Ethical approval was obtained prior to study commencement. All babies undergoing a septic screen in the first 72 hours of life were eligible for inclusion. A deep ear swab was taken from each baby and a low vaginal swab from each mother. The swabs were stored in serum tryptone glucose glycerol broth at -20C for PCR analysis. DNA extraction was performed using the Roche MagNA Pure DNA III kit and amplification using Lightcycler assays. The primers used targeted cylB gene which encodes a haemolysin specific to group B streptococcus. A second swab from both mother and baby was taken consecutively for culture using blood agar and Grenada agar culture techniques.

Results: 54 mother baby pairs were recruited and samples analysed. The rate of maternal GBS colonisation by PCR was 29% and 19% by culture. The rate of baby colonisation was 13% by PCR and 4% by culture. All culture positive mother and baby swabs were PCR positive.

Conclusions and Discussion: The appropriate use of antibiotic prophylaxis for GBS bacteraemia in the neonate remains a challenge. Without a nationwide GBS screening programme in the UK many women present at delivery with an unknown GBS status. The ability to rapidly identify maternal carriers and colonised infants in the immediate post natal period would target those who should be considered for treatment and limit unnecessary antibiotic use in those at low risk. It appears that PCR in this setting may be superior to culture based techniques. Importantly this is the first study to date to evaluate PCR in maternal postnatal GBS testing. These findings warrant further investigation and recruitment to this study continues.

Acknowledgements: ESPID, South West Midlands Neonatal Network, Eulie Peto Research Fund.

References
1. Rapid detection of group B streptococci in pregnant women at delivery. Bergeron et al. NEJM 2000 343:175 179
2. Real time Polymerase Chain Reaction for the rapid detection of Group B Streptococcal colonisation in neonates. Natarajan et al. Pediatrics 2006 118:14 22.

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