Detection of erythromycin and clindamycin resistance genes in Group B Streptococcal clinical isolates and cervicovaginal-rectal swabs.

A multiplex PCR assay was used to detect the erythromycin (EM) and clindamycin (CM) antibiotic resistance genes, ermB, ermTR, and mefA/E, in Group B Streptococcal (GBS) clinical isolates and in DNA extracted from the corresponding cervicovaginal-rectal (CVR) swabs. We compared these results to the standard EM/CM double disk diffusion assay of 46 isolates. Given that these genes are present in other CVR flora and are found on mobile genetic elements, the PCR assay was unable to predict GBS resistance directly from the swabs. Therefore, PCR can only accurately detect resistance genes and predict the resistance phenotype from purified GBS isolates.