Maternal colonisation with Streptococcus agalactiae, and associated stillbirth and neonatal disease in coastal Kenya
Seale AC., Koech AC., Sheppard AE., Barsosio HC., Langat J., Anyango E., Mwarumba S., Makio S., Morpeth SC., Anampiu K., Vaughan A., Giess A., Mogeni P., Walusuna L., Mwangudzah H., Mwanzui D., Salim M., Kemp B., Jones C., Mturi N., Tsofa B., Mumbo E., Mulewa D., Bandika V., Soita M., Owiti M., Onzere N., Walker AS., Schrag SJ., Kennedy SH., Fegan G., Crook DW., Berkley JA.
Streptococcus agalactiae (Group B Streptococcus, GBS) causes neonatal disease and stillbirth, but its burden in sub-Saharan Africa is uncertain. We assessed maternal recto-vaginal GBS colonisation (7967 women), stillbirth and neonatal disease. Whole genome sequencing was used to determine serotypes, sequence types (ST), and phylogeny. We found low maternal GBS colonisation prevalence (934/7967, 12%), but comparatively high incidence of GBS associated stillbirth and early onset neonatal disease (EOD) in hospital (0.91(0.25-2.3)/1000 births; 0.76(0.25-1.77)/1000 live-births respectively). However, using a population denominator, EOD incidence was considerably reduced (0.13(0.07-0.21)/1000 live-births). Treated cases of EOD had very high case fatality (17/36, 47%), especially within 24 hours of birth, making under ascertainment of community-born cases highly likely, both here and in similar facility-based studies. Maternal GBS colonisation was less common in women with low socio-economic status, HIV infection and undernutrition, but when GBS-colonised, they were more likely colonised by the most virulent clone, CC17. CC17 accounted for 267/915(29%) of maternal colonising (265/267(99%) serotype III, 2/267(0.7%) serotype IV), and 51/73(70%) of neonatal disease cases (all serotype III). Trivalent (Ia/II/III) and pentavalent (Ia/Ib/II/III/V) vaccines would cover 71/73(97%) and 72/73(99%) of disease-causing serotypes respectively. Serotype IV should be considered for inclusion, with evidence of capsular switching in CC17 strains.