Group B Streptococcus colonization by HIV status in pregnant women: prevalence and risk factors

To examine the prevalence of and risk factors for group B Streptococcus (GBS) colonization in an HIV-infected and uninfected pregnant population.

We conducted a retrospective double cohort study comparing the prevalence of GBS colonization between 90 HIV-infected and 1947 uninfected women attending prenatal care at San Francisco General Hospital, an urban public hospital affiliated with the University of California, San Francisco. We investigated risk factors for GBS colonization, including age, ethnicity, obesity, diabetes, alcohol or illicit drug use, tobacco use, degree of immunosuppression, and infectious comorbidities.

In the multivariable analysis, HIV serostatus was not independently associated with GBS colonization (odds ratio [OR] 1.00, 95% confidence interval [CI] 0.62-1.62). Obesity (OR 1.53, 95% CI 1.13-2.07), white race (OR 1.89, 95% CI 1.30-2.75), and black race (OR 1.78, 95% CI 1.32-2.41) were independently associated with increased maternal GBS colonization. Among HIV-infected women, univariate analysis showed an association between GBS colonization and detectable HIV-1 plasma viral load at the time of rectovaginal culture (p<0.05). Mean CD4 lymphocyte count, infectious comorbidities, and HIV-1 plasma viral load at delivery were not associated with GBS colonization in HIV-infected pregnant women.

HIV-1 infection is not a risk factor for GBS colonization among an ethnically diverse pregnant population at San Francisco General Hospital, although our data suggest that among HIV-infected women, plasma HIV-1 viremia may be associated with GBS colonization. Interventions that diminish HIV-1 plasma viral load and, perhaps, genital tract shedding of HIV may be associated with a reduced risk of GBS colonization in future studies.