Objective: To compare whether the Group B streptococcal culture detection rate from vaginal anorectal cultures, vaginal, or anorectal are equivalent.
Material and Method: Cross-sectional descriptive study was performed on 320 pregnant women with a gestational age between 28-42 weeks presenting with labor pain, between October, 1 and 30, 2004 in Rajavithi Hospital. Anorectal and vaginal swab cultures were collected and cultured in Todd Hewitt broth with 15 μg/ml nalidixic acid and 8 μg/ml gentamicin.
Results: Forty-three (13.44%) and 33 cases (10.31%) were not significantly different in GBS detection rate in vaginal and anorectal culture, respectively (p = 0.154, McNemar). Combined vaginal-anorectal culture significantly improved the colonization GBS detection rate to 18.12% compared with either individual vaginal or anorectal culture l (p < 0.001, McNemar).
Conclusion: GBS detection rate from combined vaginal-anorectal was significantly higher than either individual vaginal or anorectal cultures.

Keywords: Group B streptococcous, Vaginal culture, Anorectal culture, GBS, Rajavithi Hospital