Genetic diversity and antimicrobial resistance of invasive, noninvasive and colonizing group B Streptococcus isolates in southern Brazil

Abstract

Introduction. Group B Streptococcus (GBS) is a human commensal bacterium that is also associated with infection in pregnant and non-pregnant adults, neonates and elderly people. Gap Statement. The authors hypothesize that knowledge of regional GBS genetic patterns may allow the use of prevention and treatment measures to reduce the burden of streptococcal disease. Aim. The aim was to report the genotypic diversity and antimicrobial sensitivity profiles of invasive, noninvasive urinary and colonizing GBS strains, and evaluate the relationships between these findings. Methodology. The study included consecutive and non-duplicated GBS isolates recovered in southern Brazil from 2015 to 2017. We performed multiple-locus variable-number tandem repeat analysis (MLVA) and PCR analyses to determine capsular serotypes and identify the presence of the resistance genes mefA/E, ermB and ermA/TR, and also antibiotic susceptibility testing. Results. The sample consisted of 348 GBS strains, 42 MLVA types were identified, and 4 of them represented 64 % of isolates. Serotype Ia was the most prevalent (42.2 %) and was found in a higher percentage associated with colonization, followed by serotypes V (24.4 %), II (17.8 %) and III (7.8 %). Serotype V was associated with invasive isolates and serotypes II and III with noninvasive isolates, without significant differences. All isolates were susceptible to penicillin. GBS 2018/ hvgA was observed in 17 isolates, with 11 belonging to serogroup III. The Hunter–Gaston diversity index was calculated as 0.879. The genes mefA/E, erm/B and erm/A/TR were found in 45, 19 and 46 isolates. Conclusion. This report suggests that the circulating GBS belong to a limited number of genetic lineages. The most common genotypes were Ia/MT12 and V/MT18, which are associated with high resistance to macrolides and the presence of the genes mefA/E and ermA/TR. Penicillin remains the antibiotic of choice. Implementation of continuous surveillance of GBS infections will be essential to assess GBS epidemiology and develop accurate GBS prevention, especially strategies associated with vaccination.