Evaluation of liquid biphasic Granada medium and instant liquid biphasic Granada medium for group B streptococcus detection

Abstract

Introduction: Group B streptococci (GBS) are transmitted from the mother to the newborn. Prevention of neonatal infection is achieved by intrapartum prophylaxis given to mothers colonized with GBS at 35 to 37 weeks of pregnancy.

Materials and methods: Liquid biphasic Granada medium (LB) and instant liquid biphasic Granada medium (ILB) were evaluated for GBS detection. Vaginal swabs obtained from 300 women were inoculated onto LB or ILB, or onto Todd-Hewitt broth and analyzed with the ATB system (comparison method).

Results: Prevalence of GBS was 20% (61/300). LB and Todd-Hewitt with ATB detected GBS in 20% of women, and ILB in 19% of women. No growth was observed at four hours in any of the media studied. At 10 h and 14 h, identification of GBS was possible in 43/300 (14%) and 53/300 (18%) of ILB cultures, respectively, and in 32/300 (11%) and 46/300 (15%) of LB cultures.

Conclusion: All the media used are suitable for GBS detection. The majority of GBS were identified in ILB and LB cultures at 10 h and 14 h.