A rapid MALDI Biotyper based approach for screening anovaginal colonization by Streptococcus agalactiae in pregnant...

Colonization of pregnant women with Streptococcus agalactiae is the main risk factor for vertical transmission to neonates and the occurrence of early onset neonatal disease. Screening for maternal carriage is used to guide the administration of intrapartum antibiotics and can significantly reduce disease occurrence. Thus, we propose and evaluate a new protocol for detecting maternal colonization by S. agalactiae using the MALDI-TOF platform directly from enrichment broth, referred to as the MALDI-Biotyper Rapid Group B Identification Assay (MBT-RBA).

The ability of the MBT-RBA protocol to detect S. agalactiae was evaluated in mixed cultures. Additionally, the performance of MBT-RBA in comparison with the standard culture method was evaluated in 137 anovaginal swabs obtained from pregnant women, and positive MBT-RBA samples were confirmed by amplification of the cfb gene using qPCR.

The MBT-RBA detected S. agalactiae growth in mixed cultures with high confidence and accuracy. The prevalence of maternal colonization was 17.5 %, and MBT-RBA showed a sensitivity of 75 %, specificity of 100 %, positive predictive value of 100 %, and negative predictive value of 94.9 %.

The proposed protocol can detect anovaginal colonization with high confidence after only 6 h of incubation. This is a feasible and rapid test, complementary to culture or molecular assays, for screening pregnant women with unknown colonization status.