Colonization Rate of Group B Streptococcus (GBS) in Pregnant Women Using GBS Agar Medium

Group B streptococci (GBS) or Streptococcus agalactiae are members of the normal flora of the female genital tract. GBS normally colonizes the vagina in many women asymptomatically. During labor this organism may infect the newborn, leading to neonatal sepsis and meningitis. This study aimed to investigate the prevalence of group B streptococcus in pregnant women by a rapid and easy culture method. It seems that in cases in which GBS carriage is not suspected until the time of labor, using such a quick and specific culture method would be valuable. A total of 330 vaginal swabs were collected from women attending delivery room at Hedayat hospital, Tehran, Iran, from April through July 2008. Cotton swabs contaminated with vaginal fluid were placed into Amies transport medium and transported to the Avicenna laboratory daily. Vaginal specimens were cultured on selective GBS Agar Base medium (ISLAM) for isolation and detection of group B streptococcus. The plates were incubated at 35-37°C under anaerobic condition for 24 hours. Incubated S.agalactiae developed orange/red pigmented colonies in GBS agar plates. Among the 330 women, the results of the culture were positive for GBS in 68 women (20.6%). Statistical analyses showed no significant relationship between demographics, reproductive histories and obstetric characteristics of subjects with the test results. Solely the antibiotic therapy was associated with GBS colonization. The results are indicating that the relatively high maternal GBS colonization rate in pregnant women warrants a routine screening and prophylactic treatment of the infected women. Colonization with group B streptococcus can be identified directly by GBS agar medium and decrease the time to detection of GBS.