Objectives

To determine risk factors for GBS colonisation in Gambian mothers and in their infants from birth to day 60–89 of age.

Methods

Swabs and breastmilk from mothers/infant pairs were collected and cultured on selective agar. Negative samples were analysed for GBS DNA via real-time PCR. Positive isolates were serotyped using multiplex PCR and gel-agarose electrophoresis.

Results

Seven hundred and fifty women/infant pairs were recruited. 253 women (33.7%) were GBS-colonised at delivery. The predominant serotypes were: V (55%), II (16%), III (10%), Ia (8%) and Ib (8%). 186 infants were colonised (24.8%) at birth, 181 (24.1%) at 6 days and 96 at three months of age (14%). Infants born before 34 weeks of gestation and to women with rectovaginal and breast milk colonisation at delivery had increased odds of GBS colonisation at birth. Season of birth was associated with increased odds of persistent infant GBS colonisation (dry season vs. wet season AOR 2.9; 95% CI 1.6–5.2).

Conclusion

GBS colonisation is common in Gambian women at delivery and in their infants to three months of age and is dominated by serotype V. In addition to maternal colonization, breastmilk and season of birth are important risk factors for infant GBS colonisation.