Group B Streptococcus Carriers Among HIV-1-Infected Pregnant Women According to Gestational Age and Regional Site of Colonization: Rate of Recovery From Various Sites

Abstract

To the Editor: Today, women represent the population segment with the greatest increase in HIV infection.1 No data are available regarding rate and regional site of colonization by Streptococcus agalactiae in HIV-1-infected pregnant women at different periods during gestation. This study was conducted on 101 HIV-1-infected women selected prospectively at the Service of Infectious-Contagious Diseases in Obstetrics, School of Medicine of Ribeirão Preto, University of São Paulo. The samples for group B Streptococcus (GBS) analysis were obtained by double collection (a vaginal swab and an anal swab). The collections were performed between the 24th and 28th weeks and between the 35th and 37th weeks of pregnancy. The collected swabs were immersed in 2-mL tubes containing Todd Hewitt Broth, an enriched medium, to which 8 μg/mL of gentamicin and 15 μg/mL of nalidixic acid were added. The swabs were later sent to the microbiology section where 250 mcl sheep blood were added to each tube. The content was homogenized and left to stand at 35°C for 18 h. After this time, the samples were seeded onto blood-agar plates containing gentamicin and nalidixic acid at the concentrations specified above, incubated in an over at 35°C for 48 h and then analyzed for bacterial growth.When the growth of bacteria with a β-hemolytic pattern was detected, the samples were analyzed and the results were confirmed by latex agglutination using the Streptex typing kit.2 This study was approved by the Research Ethics Committee of the institution, and the women willing to participate in the study signed an informed consent form. The prevalence of GBS colonization observed between 24 and 28 weeks (16.8%) and between 35 and 37 weeks (19.8%) demonstrates that gestational age did not lead to higher rates of GBS colonization (χ2 = 0.30, P = 0.58). We observed that only 29% of HIV-1-infected patients colonized between 24 and 28 weeks continued to be colonized between 35 and 37 weeks. Regional positivity was significantly higher for the anal site, with a mean 40% increase in the diagnosis of GBS colonization when the anal site was added to the vaginal site (Fisher test: P = 0.037). In the present study, gestational age did not influence the rates of maternal colonization with GBS among HIV-1-infected women. The distribution of sites with positive cultures for GBS demonstrates that regional positivity was significantly higher for the anal site compared with the vaginal site. The study data do not enable us to select a small group of women with a high probability of colonization. These results highlight the need for routine anal screening for GBS colonization between 35 and 37 weeks in HIV-infected pregnant women. Patrícia El Beitune, MD, PhD Geraldo Duarte, MD, PhD Cláudia Maria Leite Maffei, MD, PhD School of Medicine of Ribeirão Preto University of São Paulo, Ribeirão Preto São Paulo, Brazil