Phenotypic traits and comparative detection methods of vaginal carriage of Group B streptococci and its associated micro-biota in term pregnant Saudi women

Abstract

Group B streptococcus (GBS) is a significant cause of serious infections in neonates and the composition of the vaginal micro-biota also affect neonatal outcome. To investigate vaginal carriage of Group B streptococcus in 217 term Saudi pregnant women, the direct antigen detection method in selective enrichment broth, Todd-Hewitt broth with 8 µg/ml gentamicin and 15 µg/ml nalidixic acid, using 2 commercial kits was used and compared to Centers for Disease Control and Prevention, CDC-gold standard method where following enrichment conventional means for identify­ing GBS is through isolation on subculture to blood agar plates, which requires 72 h before a final result is achieved. Phenotypic traits of Group B streptococcus serotypes distribution, antibiotic susceptibility patterns, biofilm formation and its associated vaginal micro-biota were also studied. The CDC-gold standard method positivity rate of Group B streptococcus was 23%, with no significant correlation with any of the studied demographic factors. In comparison, direct antigen detection method in boiled selective enrichment broth growth revealed 52.2 and 100% sensitivity and 100% specificity after growth amplification for 4 and 18 h incubation, respectively. Of 50 Group B streptococcus isolates, serotype II was the most predominant (42%), followed by serotype IV (16%). No resistance to ampicillin, cefepime, ceftriaxone or vancomycin was found, but 10, and 6%, of the strains were resistant to erythromycin and clindamycin, respectively. Overall 54% of Group B streptococcus strains were biofilm producers, but (100%) among serotype Ib, III, or V. Of several coexistent, Escherichia coli and Enterococcus feacalis were the most frequently Group B streptococcus -associated organisms, but with no statistical correlation. Key words: Group B Streptococcus, GBS-serotypes, antibiotics susceptibility, GBS-biofilm, vaginal micro-biota, Escherichia coli, Enterococcus feacalis.