Serotypes and antimicrobial susceptibility of group B Streptococcus from pregnant women in Mexico.

Title: Serotypes and antimicrobial susceptibility of group B Streptococcus isolated from pregnant women in México

Background: Group B streptococci (SGB) are a leading cause of neonatal sepsis and meningitis. Women colonized might also develop pregnancy-associated infections including urinary tract infection, bacteremia and postpartum endometritis. There are nine different capsular types, and with the possibility of a GBS vaccine in the future; it is essential to understand which of these types are circulating. We determined the serotype distribution of isolated rectovaginal and urine GBS obtained from an obstetric population, and also their antibiotic sensitivity patterns.

Methods: A total of 101 strains were studied: SGB were confirmed by latex agglutination (Slidex Strepto-Kit bioMérieux), and the serotype was confirmed by latex agglutination (Pastorex Streptococcus B. Becton Dickinson, EUA). Antimicrobial susceptibility testing was performed by a Kirby-Bauer disk diffusion.

Results: All SGB were serologically typeable; 61.3% were type I, 25.7% were type II and only 12.8 were type III. All of them were 100% susceptible to beta lactam agents. Only 5.9% strains were resistant to erythromycin.

Conclusion: In the last years, no major changes have been observed in the distribution of serotypes of SGB in México, serotype I is still the most common. This makes us think of the possibility of a vaccine that includes serotypes I and II that represent close to 90% of the isolations.