Strong Correspondence of the Vaginal and Rectal Load of Group B Streptococci in Pregnant Women

Background: To establish the potential role of the rectum as a reservoir for vaginal Streptococcus agalactiae (group B streptococci, GBS), both sites were sampled simultaneously and the bacterial loads of GBS were established by quantitative PCR (qPCR), for 100 pregnant women at 35 - 37 weeks of gestation. Methods: Vaginal and rectal occurrence of GBS was detected by qPCR, for 100 pregnant women at 35 - 37 weeks of gestation. DNA was extracted from vaginal (V), rectal (R) and vaginorectal (VR) swabs using the NucliSENS EasyMAG platform and cfb -qPCR, specific for GBS, was carried out for the quantification of GBS. Results: Ten women were found positive for both R and V swabs, 7 positive for R swabs only and 4 positive for V swabs only. Significant positive correlation was found between vaginal and rectal loads of GBS (r = 0.701 , P < 0.0001 ). In addition, the bacterial load of the 28 positive VR swabs (mean log10 cells/mL: 6.24, SD: 0.99; median: 5.82) was always higher than that of the V (mean: 5.72, SD: 0.87; median: 5.56) or R swabs (mean: 5.52, SD 0.72; median: 5.16) separately (P < 0.05). Conclusions: Using qPCR, significant correlation between quantities of vaginal and rectal GBS loads was established. Comparison of sampling methods indicates that VR swabbing yields higher GBS loads and 7 more positive women than separate V and R swabbing, and therefore is preferable for sample collection for GBS detection in pregnant women. doi: http://dx.doi.org/10.4021/jcgo185e