Usefulness of enrichment culture for GBS screening based on a multicenter study

Abstract

Group B streptococci (GBS) are the most common causative pathogen of neonatal meningitis and sepsis through vertical transmission. The current CDC guidelines for the prevention of perinatal GBS (“Prevention of Perinatal Group B Streptococcal Disease-Revised Guidelines from CDC, 2010”) recommends screening of all pregnant women for GBS colonization at 35–37 weeks’ gestation using enrichment cultures. We compared the enrichment medium for GBS used at six centers and discuss their usefulness. In addition, a direct latex agglutination test was introduced to identify non-hemolytic GBS that may be missed by usual procedures, and thus the GBS detection was performed using three methods: one direct culture and two enrichment cultures (subculture and direct latex agglutination). In a comparison between the direct and enrichment culture methods using the enrichment culture at five of the six centers, we found a 1.0- to 2.0-fold increase in the positivity rate of GBS with an average of 1.4-fold. An additional study was conducted at our hospital for one year, but the number increased 1.6-fold, which however was not significantly different from those from other centers. The results of the subculture and direct latex agglutination methods did not deviate from the GBS identification results in all centers, suggesting that the subculture method can be omitted. The enrichment culture method has a higher rate of detection of infection and seems to be useful in improving the accuracy of perinatal GBS screening.