This study was performed to investigate the serotype distribution of group B streptococcus (GBS) isolated from pregnant Korean women using molecular methods.

The study materials included 42 GBS isolates obtained from the vagina and anorectum of pregnant women in Seoul, Korea between 2005 and 2006. Four clinical isolates with known serotypes (Ia, Ib, III, and V) were used for validation of molecular serotyping. We used serotype-specific primers for identification of the serotypes (Ia, Ib, III, V, and VI). To determine the ambiguous serotypes by serotype-specific PCR, sequence analysis of the PCR amplicons which had been amplified with GBS-common primers was used.

The serotypes determined by the molecular methods agreed with the previously known 4 serotypes (Ia, Ib, III, and V). The serotypes of all 42 isolates were successfully determined by molecular methods. The distribution of the GBS serotype was as follows in order of frequency: serotype III was found in 12 isolates (28.6%), serotype V was found in 11 isolates (26.2%), serotype Ia was found in 11 isolates (26.2%), serotype VI was found in 4 isolates (9.5%), serotype Ib was found in 2 isolates (4.8%), and serotype II was found in 2 isolates (4.8%).

Serotypes III, V, and Ia were the most frequently identified serotypes in pregnant Korean women. Molecular serotyping is useful for surveillance of the serotype distribution of GBS in colonized pregnant women and GBS diseases of neonates.