Abstract
BackgroundGroup B Streptococcus (GBS) remains a major cause of neonatal sepsis and is also associated with invasive and noninvasive infections in pregnant women and non-pregnant adults, elderly and patients with underlying medical conditions. Ten capsular serotypes have been recognized, and determination of their distribution within a specific population or geographical region is important as they are major targets for the development of vaccine strategies. We have evaluated the characteristics of GBS isolates recovered from individuals with infections or colonization by this microorganism, living in different geographic regions of Brazil.MethodsA total of 434 isolates were identified and serotyped by conventional phenotypic tests. The determination of antimicrobial susceptibility was performed by the disk diffusion method. Genes associated with resistance to erythromycin (ermA, ermB, mefA) and tetracycline (tetK, tetL, tetM, tetO) as well as virulence-associated genes (bac, bca, lmb, scpB) were investigated using PCR. Pulsed-field gel electrophoresis (PFGE) was used to examine the genetic diversity of macrolide-resistant and of a number of selected macrolide-susceptible isolates.ResultsOverall, serotypes Ia (27.6%), II (19.1%), Ib (18.7%) and V (13.6%) were the most predominant, followed by serotypes IV (8.1%) and III (6.7%). All the isolates were susceptible to the beta-lactam antimicrobials tested and 97% were resistant to tetracycline. Resistance to erythromycin and clindamycin were found in 4.1% and 3% of the isolates, respectively. Among the resistance genes investigated, tetM (99.3%) and tetO (1.8%) were detected among tetracycline-resistant isolates and ermA (39%) and ermB (27.6%) were found among macrolide-resistant isolates. The lmb and scpB virulence genes were detected in all isolates, while bac and bca were detected in 57 (13.1%) and 237 (54.6%) isolates, respectively. Molecular typing by PFGE showed that resistance to erythromycin was associated with a variety of clones.ConclusionThese findings indicate that GBS isolates circulating in Brazil have a variety of phenotypic and genotypic characteristics, and suggest that macrolide-resistant isolates may arise by both clonal spread and independent acquisition of resistance genes.
Highlights
Group B Streptococcus (GBS) remains a major cause of neonatal sepsis and is associated with invasive and noninvasive infections in pregnant women and non-pregnant adults, elderly and patients with underlying medical conditions
In the present report we describe the serotype distribution, antimicrobial susceptibility, presence of virulencerelated and antimicrobial resistance genes among GBS isolates collected from the five geographical regions in Brazil
Overall, serotypes Ia (120 isolates; 27.6% ± 4.2, 95% confidence intervals (95% CI)), II (83 isolates; 19.1% ± 3.7), Ib (81 isolates; 18.7% ± 3.7) and V (59 isolates; 13.6% ± 3.2) were the most predominant among the 434 GBS isolates included in the present study, followed by serotypes IV (35 isolates; 8.1% ± 2.6) and III (29 isolates; 6.7% ± 2.3)
Summary
Group B Streptococcus (GBS) remains a major cause of neonatal sepsis and is associated with invasive and noninvasive infections in pregnant women and non-pregnant adults, elderly and patients with underlying medical conditions. Streptococcus agalactiae (Group B Streptococcus, GBS) is a leading cause of neonatal morbidity and mortality [1], and is an important opportunistic agent of infections in pregnant women, as well as non-pregnant adults, especially the elderly or those with underlying medical conditions [2]. This microorganism is commonly found as a colonizer of the genital and the gastrointestinal tracts of both men and women, and vertical transmission from a colonized mother to her newborn during labor can result in life threatening infections. In Brazil, the occurrence of serotypes Ia, Ib, II, III, IV and V has been described in a few studies conducted with isolates originated from the South and the Southeast regions [10,11,12,13,14,15]
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