Primary carrier sites of group B streptococci in pregnant women correlated with serotype distributions and maternal parity.

Perianal, perineal, vulval, and vaginal swabs from women attending an antenatal clinic were quantitatively cultured for group B streptococci using Islam's medium. The isolation rates from the four sites were very similar with an overall carriage rate of 21%. The findings suggest that the type II strains, a faecal flora, probably colonise the perianal site from a faecal source, and that the type III strains colonise primarily the genital site and then spread to the perineoperianal region. The type I strains did not conform to any pattern, suggesting a possible secondary involvement of these sites from another source. The types I, R, X, and non-typable isolates were almost exclusively isolated from primigravidae and second gravidae; the type III strains were conspicuously absent in 47 primigravidae. The primigravidae and second gravidae women consistently had high colony counts.