Epidemiology and Resistance Mechanisms of Group B Streptococci in Late-pregnant Maternal Birth Canal

Objective To study the antibiotic-resistant rate of group B Streptococci (GBS) in obstetric canal of late-pregnant women, evaluate the antibiotic-resistant status and finally to support the GBS prevention and curing by proper antibiotics. Methods 31 pregnant women between 35 to 37 gestational weeks were included, for whom the antibiotic sensitivity as well as the drug (erythromycin and clindamycin) resistance genes of GBS in obstetric canal was analyzed. Results 12 (38.7%) strains of GBS were resistant to clindamycin, while 21 (67.7%) to erythromycin, within which 12 strains were intrinsic phenotype ——cMLS type-clindamycin resistance, other 9 were active efflux phenotype ——MS type-clindamycin sensitive and all of which were confirmed by Double disk diffusion method. Eleven strains were mef (A) positive, and 12 strains were erm (B) positive, in which 3 with erm (C). Conclusions In our research the GBS strains show a high erythromycin and clindamycin resistance rate. The resistance of our GBS strains are mainly caused by the ribosomal target changes induced by erm (B) and the increased efflux of clindamycin induced by mef (A).