Serotype distribution and antimicrobial susceptibility profiles of group B streptococcus strains from pregnant women in Beijing, 1994-99

Objectives To investigate the serotype distribution among group B streptococcus (GBS) strains isolated in Beijing areas from 1994 to 1999 in order to determine the optimal components of future GBS vaccine; also, to assess the antimicrobial susceptibility profile of the strains. Methods A total of 155 CBS strains were isolated from 1994 to 1999. Serotyping was performed by double diffusion in agarose (Ouchterlony method). Susceptibility to ampicillin, penicillin G, oxacillin, erythromycin, clindamycin, cephazolin, cefuroxime, cefoperazone, gentamicin and amikacin was assessed by disc diffusion. Results Seven serotypes were identified. Type II (II/C; 36%), type III (III/R; 26%), type la (la/c; 18%) were the most common. All strains were susceptible or moderately susceptible to ampicillin, penicillin G, oxacillin, cephazolin, cefuroxime and cefoperazone. A dramatic increase in erythromycin and clindamycin resistance occurred when comparing the period 1994-97 and 1998-99. For serotype III/R, the proportion resistant to macrolides was 22.5%. Conclusion GBS serotypes la, II and III may be important components of a future multivalent GBS vaccine for use in Beijing areas. The susceptibility of the GBS strains to penicillin G and ampicillin supports continued use of either of these antibiotics for prevention of early-onset GBS disease. The use of erythromycin as a second-line agent can be questioned with regard to the increased bacterial resistance. Continuous surveillance for changes in susceptibility is of considerable clinical importance.