Abstract
Group B Streptococcus (GBS) is a causative bacterium for meningitis and sepsis in neonates, and GBS screening of all pregnant women at 35–37 weeks of gestation is recommended to prevent neonatal GBS infection. We have used a culture method employing a selective enrichment medium with subculture to a selective separation medium for GBS screening since 2015, to improve detection efficiency. However, GBS selectivity may be reduced by the overgrowth of other bacterial species other than GBS during the culture process. To investigate this possibility, the detection of GBS at various bacterial concentrations by coculturing of Escherichia coli (E. coli), Candida albicans (C. albicans), Enterococcus faecalis (E. faecalis) and Streptococcus pyogenes (S. pyogenes) was evaluated using three commercial sets of selective separation and enrichment media. Using < 3 × 101 colony forming unit (CFU)/mL of GBS, all three media sets detected GBS cocultured with E. coli, C. albicans, and S. pyogenes after 24 h, but at < 3 × 105 CFU/mL of GBS, colonization was not detected using the sets with cocultured E. faecalis after 24 or 48 h. These results show that the overgrowth of E. faecalis in the culture process reduces the sensitivity of these sets for GBS detection, indicating that although all three media sets are reliable and sensitive for GBS detection, additional culture may be necessary when E. faecalis contaminates vaginal and anorectal clinical specimens.
