Active screening of group B Streptococci with reduced penicillin susceptibility and altered serotype distribution isolated from pregnant women in Kobe, Japan

Group B streptococcus (GBS; Streptococcus agalactiae) is a leading cause of neonatal invasive infections and was believed to be fully susceptible to penicillin. However, we recently identified several clinical GBS isolates with reduced penicillin susceptibility (PRGBS), which were mainly isolated from respiratory specimens of elderly people. An investigation of both the isolation rate of PRGBS and the serotype distribution among pregnant women is crucial to decisions regarding optimal prevention and strategies for GBS treatment in neonates. We collected 141 GBS isolates from vaginal specimens of 122 pregnant women in a hospital in Kobe, Japan, from 2007 to 2008. Of the 141 GBS isolates, 139 were subjected to antimicrobial susceptibility testing based on the results of screening for PRGBS by the disk diffusion method. All 139 isolates were susceptible to penicillin G, ampicillin, cefotaxime, cefepime, and meropenem; no PRGBS isolates were detected. However, the rates of erythromycin and clindamycin resistance in the isolates were 10.1z and 5.0z, respectively, which are much higher than the values previously reported in Japan. Serotypes VI and VIII accounted for 26z of GBS; a markedly decreased percentage from the rates observed around the year 2000. These findings suggested that penicillin remains an effective means of intrapartum antibiotic prophylaxis in Japan.