Group B Streptococcus Genital Colonization patterns among Non-Pregnant Women of Reproductive Age at Kawempe National Referral Hospital
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Background; Maternal rectovaginal colonization with Group B streptococcus (GBS) is a prerequisite for neonatal disease. Maternal intrapartum antibiotic prophylaxis (IAP) as the current main mode of prevention has limitations. A maternal GBS vaccine could prevent GBS colonization and its complications. One model to test the GBS vaccine would be a controlled human infection model in non-pregnant women. To develop this, we need to understand how host immunity affects GBS colonization. This study aimed to investigate how GBS natural colonization varied over time among non-pregnant women at Kawempe National Referral Hospital (KNRH). Objective: To determine how colonization with GBS changes over time among non-pregnant women of reproductive age. Materials and Methods; This prospective cohort study was conducted in the Gynaecology clinics of KNRH. Participants were non-pregnant women of reproductive age that consented and were selected by consecutive sampling. Vaginal, rectal and blood samples were obtained over 12 weeks to monitor colonization with GBS over the same time period. Results; Of the 180 women screened, 90 eligible women were recruited (25 colonized with GBS at baseline and 65 not colonized with GBS at baseline). The GBS colonization rates ranged between 17.6% to 30.8%. The GBS rate of acquisition was 42.2% overall and 27.3% in persons living with HIV. The GBS rate of loss was very high at 95% overall, and 85.7% in persons living with HIV. Six GBS serotypes were isolated, the commonest being type. Conclusion; GBS colonization in non-pregnant women is very transient with very high rates of acquisition and loss. Non-colonization observed in healthy non-pregnant women in a three months period may be natural immunity dependent. All the six isolated GBS serotypes are vaccine included and no non-vaccine serotype was identified. Therefore the hexavalent vaccine undergoing clinical trials could be effective at reducing the burden of GBS disease in infants. Recommendation; Given the high burden of colonization and presence of all the GBS serotypes in the vaccine, maternal vaccination could prevent colonization in pregnancy. More studies are required to assess serotype-specific GBS antibody response at the mucosal (vaginal) and systemic levels for us to fully comprehend if natural immunity to GBS is serotype specific.