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, CDCgold 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.