A Multicenter Study on the Utility of Selective Enrichment Broth for Detection of Group B Streptococcus in Pregnant Women in Japan

Universal screening for Streptococcus agalactiae, Group B Streptococcus (GBS), in pregnant women is important for the prevention of severe infectious diseases in neonates. The subculture method using selective enrichment broth significantly improves GBS detection rates in the United States; however, this method is not widely utilized in Japan mainly because of the lack of large-scale validation. Therefore, we aimed to validate the utility of the subculture method in collaboration with multiple facilities. A total of 1957 vaginal-rectal swab specimens were obtained from pregnant women at 35-37 gestational weeks from March 1, 2020, to August 30, 2020, at Fukushima Medical University Hospital, Aiiku Hospital, Kitano Hospital, and the University of the Ryukyus Hospital. Conventional direct agar plating, subculture using selective enrichment broth, and direct latex agglutination (LA) testing with incubated broth were performed for GBS detection, and discrepant results were confirmed using real-time PCR. The GBS detection rates for direct agar plating, subculture, and direct LA testing were 18.2% (357/1957), 21.6% (423/1957), and 22.3% (437/1957), respectively. The use of selective enrichment broth showed promise for GBS detection with high sensitivity and is therefore recommended for GBS screening to prevent GBS-related infectious diseases in neonates in Japan.