Background

Group B Streptococcus (GBS) is a leading agent of early-onset neonatal disease, which is currently prevented by the intrapartum antibiotic prophylaxis (IAP). IAP is recommended to pregnant women who are colonized by GBS at 36-37 gestational weeks. However, GBS colonization can be transient or intermittent; thus, previously negative women can be positive at delivery, or vice-versa. Culture-based techniques have a long turnaround-time (TAT); thus, developing a cost-effective and fast screening method that could be applied closer to delivery can aid to antimicrobial stewardship. Here we present a MALDI-TOF-based protocol for GBS detection directly in pre-enriched clinical samples.

Methods

We analyzed 612 rectovaginal samples of pregnant women in Brazil by the gold-standard culture-based technique and by the new MALDI-based approach. In the last, direct detection of GBS from clinical samples was performed by pre-enriching samples for 18h and applying the resulting pellet onto the MALDI target after centrifuging and washing.

Results

Sixty-five samples were positive in culture (10.6%) and 50 (8.2%) in the alternative MALDI approach. Number of total agreements was 597 (97.55% of the observations). The sensitivity and specificity of the proposed method were high (81% and 100% respectively). The Kappa coefficient was 0.856 (95% CI). The mean TAT of culture was 48h, while the TAT of the alternative MALDI approach was 19h.

Conclusions

Detection of GBS directly in clinical samples using MALDI-TOF MS seems a suitable, fast, and reliable alternative for GBS screening among pregnant women that could be applied closer to the moment of birth.