Background: Group B Streptococcus (GBS ) has been described as an important pathogen in newborns and pregnant women. Maternal vaccination against GBS can reduce maternal GBS colonization and enhance antibody transfer to the fetus and also prevent the subsequent infections. Nine serotypes can be identified based on capsular polysaccharide: Ia, Ib, II-VIII. Due to the changes in serotypes' distribution pattern over time and also variation in different geographic areas, production of a universally optimal vaccine is impossible. This study aimed to evaluate the serotype distribution of GBS using the multiplex PCR among the pregnant women.

Materials and Methods: This study was performed on 382 pregnant women. Vaginal swab samples were placed in the LIM selective medium and incubated at 37°C for 24 h. Then the samples were cultured in blood Agar medium and the GBS was identified and confirmed using the standard tests and gene encoding dlts , respectively. Capsular typing was perform ed using the multiplex PCR method to identify the Ia,Ib,II-VIII serotypes.

Results: Thirty-six ( 9.4 % ) out of 382 pregnant women were carriers of GBS. The most common types were III (32.14%), V (21.43%), and IV (14.3%), respectively. Types II and VIII were not identified in this study.

Conclusion: Considering the high prevalence of III , V and IV serotypes in this study, they are potential sources for the production of multivalent GBS vaccines in near future.