BACKGROUND Group B Streptococcus (GBS) is a normal component of the gastrointestinal and genital microbiota in humans and can lead to important infections in newborns. AIM To compare GBS isolation and identification methods as well as to assess the antibiotic susceptibility and to identify resistance genes in GBS strains from pregnant women attended in healthcare services from the city of Vitória da Conquista, in Bahia State, Brazil. METHODS From January 2017 to February 2018, vaginorectal swabs were obtained from 186 participants and the samples were seeded onto chromogenic agar for GBS before and after inoculation in selective broth. Confirmatory identification using 3 CAMP and latex tests was performed in samples with GBS-suggestive colonies. Then, disk diffusion antibiograms were performed in GBS-positive samples, and the detection of the resistance genes erm B, erm TR, mef A, and lin B in the clindamycin and/or erythromycin-resistant samples was carried out. RESULTS Thirty-two samples (17.2%) were GBS-positive. The culture in chromogenic agar after sample incubation in selective broth was the most sensitive method (96.9%) for GBS detection. All isolates were susceptible to penicillin, ampicillin, cefotaxime, and vancomycin. Clindamycin resistance was observed in 6 samples (18.8%), while 8 samples (25%) were erythromycin-resistant. All erythromycin and/or clindamycin-resistant GBS strains had negative D-tests. Two strains (25%) presented an M phenotype and 6 isolates (75%) presented a cMLSB phenotype. The erm B gene was identified in 4 samples (44.4%), the mef A gene was also found in 4 samples (44.4%), the erm TR gene was identified in 1 isolate (11.1%), and the lin B gene was not found in any isolate. CONCLUSION This study evidenced that the screening for SGB can be performed by means of various methods, including chromogenic media, and that the chemoprophylaxis for pregnant women who cannot use penicillin must be susceptibility-guided.

Objectives: to estimate the prevalence and the factors associated with the colonization by group B streptococcus (GBS) in pregnant women from the urban area attended at health units in a municipality in northeastern Brazil. Methods: it is a cross-sectional study conducted from January 2017 to March 2018. Vagino-rectal swabs were collected from 210 pregnant women between 32 and 40 weeks of gestation. The swabs were seeded on 5% sheep blood agar and on chromogenic agar. For confirmatory identification of GBS, the CAMP test and latex agglutination were used. Descriptive analysis and univariate and multivariate association analysis were performed using a multinomial logistic model. Results: the prevalence of GBS colonization among pregnant women was 18.1% (n = 38), and a statistically significant association (p<0.05) was found for income and parity variables in the group of older women in the univariate analysis, and for skin color, age and parity in the final multivariate analysis. Conclusions: the prevalence of maternal colonization by GBS was similar to that described in other studies. Although some risk factors, such as skin color, age and parity, were associated with colonization, other studies are essential to establish more information on pregnant women more likely to be colonized by GBS.

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