Characterization of group B streptococcus isolated from women in Saitama city, Japan

Streptococcus agalactiae (group B streptococcus; GBS) is a common cause of neonatal sepsis and meningitis. Intrapartum antibiotic prophylaxis is effective in reducing neonatal GBS disease. Penicillin is recommended for intrapartum antibiotic prophylaxis; however, other antibiotics are administered to pregnant women with penicillin allergy. Serotyping and antibiotic susceptibility testing were performed on 376 GBS isolates collected from vaginal swabs in Saitama City. Of the 376 isolates, 328 (87.2%) were obtained from obstetrics and gynecology clinics. Although approximately 80% of the isolates (299/376) were from women of reproductive age (age, 15-49 years), no definite information on their pregnancy status was obtained. The most frequent serotype was V (19.1%) followed by Ib (18.6%), III (16.2%), VI (14.9%), and Ia (14.6%). None of the isolates were resistant to penicillins and cephalosporins. Isolates that were resistant to erythromycin (12.8%), clindamycin (9.0%), ofloxacin (19.4%), levofloxacin (18.4%), and tetracycline (46.5%) were detected. There was a high prevalence of resistance to erythromycin (39.3%) and clindamycin (27.9%) in serotype III. In addition, almost all serotype Ib isolates were resistant to ofloxacin and levofloxacin (both, 91.4%). Pulsed-field gel electrophoresis analysis on certain GBS isolates (serotype Ib, III, and V) indicated that there was genetic diversity among the resistant isolates obtained from a limited area of Japan. In conclusion, present intrapartum antibiotic prophylaxis with penicillins would be effective in Japan; however, performing susceptibility testing before administering other antibiotics is important in order to ensure activity against the relevant isolate.