Use of GBS media for rapid detection of group B streptococci in vaginal and rectal swabs from women in labor.

In order to evaluate the differences in efficacy, three methods were used to detect group B streptococci (GBS) in women in labor. The recommended method for detecting GBS carriage in pregnant women is to culture vaginal and anorectal swabs in a selective broth medium and to subculture them onto blood agar. This method was compared with the use of GBS agar and GBS broth, both of which produce an orange pigment in response to GBS strains. A total of 319 women in labor were screened. Among the 638 specimens tested, 134 (21%) were positive in the selective Todd-Hewitt broth subcultured onto sheep blood agar, 133 (20.8%) were positive on the GBS agar and 126 (19.7%) were positive in the GBS broth. Altogether, 89 (27.9%) women in labor were found to be colonized with GBS; 87 (97.8%) of them were identified as carriers using the Todd-Hewitt broth, 87 (97.8%) with the GBS agar and 86 (96.6%) with the GBS broth. These results indicate that both GBS agar and GBS broth are reliable methods that can be used to screen for maternal and neonatal GBS colonization.