Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry with Time-of-Flight Peak Analysis for Rapid and Accurate Detection of Group B Streptococcus in Pregnant Women.

Severe infections in neonates caused by Streptococcus agalactiae, Group B Streptococcus (GBS), are often associated with GBS transmission from their mothers during labor or birth. Hence, it is necessary to develop a universal method for screening vaginal-rectal GBS colonization in pregnant women worldwide. A subculture of vaginal-rectal swabs using a selective enrichment broth and an agar plate is conventionally recommended for GBS screening. However, infants born to mothers who are GBS negative on subculture sometimes contract GBS infections. Therefore, we developed another method with high sensitivity for GBS screening. A total of 178 vaginal-rectal swabs from pregnant women were inoculated into the enrichment broth, of which 126 were suspected of containing GBS due to the change in the color of the broth. The subculture results were positive for GBS in 34 (27.0%) swabs. Each broth was then analyzed using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Analysis of the TOF peaks specific to GBS revealed 45 (35.7%) swabs as GBS positive. Of the 11 GBS positive samples on TOF peak analysis but negative on subculture, S. agalactiae gene targets were detected through PCR in 4 samples. MALDI detection with analysis of peaks of TOF (MDAPT) can detect GBS directly from cultured broth with high sensitivity. MDAPT can be an alternative method for GBS screening in pregnant women and contribute to the prevention of severe GBS infectious diseases in neonates.