Group B Streptococcus (GBS) is the leading cause of neonatal sepsis in the developed world. Little is known about the epidemiology and microbiological characteristics of the involved strains in the developing countries, where the majority of deaths from neonatal infections occur. The goals of this study were to assess the prevalence of recto-vaginal colonization with Group B Streptococcus (GBS) in pregnant women going into labor; to determine the capsular serotype of the recovered strains; and evaluate the performance of a commercial qualitative polymerase chain reaction (PCR) assay as a screening test. Between April and November 2012 we studied 87 pregnant women who delivered at the ‘Dr. Manuel Quintela University Hospital’. Recto-vaginal samples were processed by standard microbiological procedures as well as commercial PCR assay for GBS direct detection. Antimicrobial susceptibility tests on the recovered GBS strains were performed by disk-diffusion to penicillin, erythromycin and clindamycin. GBS isolates were serotyped by a previously described PCR procedure which identifies the following serotypes: Ia, Ib, II, III, IV, V, VI, VII and VIII. We recovered GBS in 9 out of 87 women (10.3%; 95% CI: 3.9-16.7). All the recovered GBS were susceptible to the antibiotics tested. The serotype distribution was as follows: serotype III, 3 isolates; serotypes Ia, Ib, IV and V, one isolate of each. The performance values of the commercial PCR assay applied directly to samples were: sensitivity 100%, specificity 97%, positive predictive value 82%, and negative predictive value 100%. If we take all PCR results as true positives, the performance of this PCR assay would be even better than standard culture method. In this case, the prevalence of GBS carriage in this population rises up to 13.2%. Although results are ready in 45 minutes, PCR assay requires the use of sophisticated laboratory equipment and does not allow the determination of the antimicrobial susceptibility pattern or the determination of the capsular serotype of the involved strains.
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