Recent Epidemiological Changes in Group B Streptococcus Among Pregnant Korean Women

Although group B (GBS) colonization rate among pregnant Korean women is lower than that among women from many Western countries, recent data show an upward trend. We investigated recent epidemiological changes in GBS among pregnant Korean women in terms of colonization rate, antimicrobial susceptibility, serotype, and resistance genotype. Vaginal and anorectal swab specimens from 379 pregnant Korean women were cultured on Strep B Carrot Broth with GBS Detect (Hardy Diagnostics, USA), selective Todd-Hewitt broth (Becton Dickinson, USA), and Granada agar plate medium (Becton Dickinson). The antimicrobial susceptibility, serotypes, and macrolide-lincosamide-streptogramin B (MLSB) resistance genes of the GBS isolates were tested. The GBS colonization rate among pregnant Korean women was 19.8% (75/379). Colonization rates using Strep B Carrot Broth with GBS Detect, selective Todd-Hewitt broth, and Granada agar plate medium cultures were 19.5%, 19.3%, and 15.0%, respectively. Six pregnant women were colonized by non-beta-hemolytic GBS and were detected only in Strep B Carrot Broth with GBS Detect. Resistance rates of GBS to clindamycin, erythromycin, and tetracycline were 16.0%, 28.0%, and 42.7%, respectively. The most common GBS serotypes were V (22.7%), VIII (20.0%), and III (20.0%). The frequency of MLSB resistance genes (B) and (TR) were 63.6% and 36.4%, respectively. The GBS colonization rate among pregnant Korean women has risen to levels observed in Western countries. To accurately evaluate GBS epidemiology among pregnant Korean women, periodic studies in multiple centers, including primary clinics, are necessary.