PURPOSE: to determine the prevalence of group B Streptococcus (GBS) in pregnant women in the third trimester of pregnancy and explore the factors potentially associated with colonization. METHODS: a sample of 273 pregnant women in the third trimester of pregnancy, from the prenatal care center in Southern Brasil, was investigated. Vaginal and anorectal samples were collected and innoculated in Todd-Hewitt selective broth supplemented with 10 µg/mL colistin and 15 µg/mL nalidixic acid and afterwards cultured on defibrinated sheep blood agar plates. All suspected colonies were submitted to the agglutination test for detection of the specific group B antigen. The Camp test was used for GBS identification in non-hemolytic varieties. Demographic, socioeconomic, reproductive, and clinico-obstetric data were also analyzed. Prevalence ratio (PR) was used as risk measurement. Confidence interval was considered significant at the level of 95% (alpha=0.05). RESULTS: prevalence of Streptococcus (GBS) colonization amounted to 21.6% (59), 9.9% (27) of pregnant women showing positivity in both sites; vaginal site colonization was found in 6.95% (19) of the women and 4.75% (13) of the samples showed positivity only in the anal site. GBS prevalence was slightly higher in pregnant women under 20 years, in those with less schooling and in primiparae and was twice as high among those who did not reported spontaneous abortion, but with no statistical significance. No difference was found in GBS prevalence according to the history of sexually transmittted diseases and tabagism. When analyzed together, the factors detected as potentially associated with colonization by GBS were: primiparae over 30 years (PR=1.55) and women with more than one sexual partner and increased frequency of sexual activity (p<0.05) (55,6 vs 20.5%; p<0.05). No difference regarding prevalence was found to exist in relation to the history of sexually transmitted diseases, previous spontaneous abortion and tabagism. CONCLUSION: these results confirm the need for routine collection for GBS culture from both sites (vaginal and anal) in all pregnant women in the third trimester of pregnancy.
Streptococcus agalactiae; Pregnancy; Prevalence; Colonization
