Virulence profiles and antimicrobial resistance of Streptococcus agalactiae infective and colonizing strains from Argentina

Abstract

Streptococcus agalactiae (GBS) is a colonizing agent in pregnant women, the main cause of invasive neonatal infections, and the reason of serious diseases in non-pregnant adults. Several virulence determinants are involved in the pathogenesis. These include capsular polysaccharide, surface-localized proteins, and toxins. Penicillin is considered the first choice antibiotic for the treatment and prophylaxis; erythromycin, clindamycin and fluoroquinolones are recommended alternatives for penicillin-allergic GBS carriers or patients. Our objective was to investigate the virulence genetic characteristics and the antimicrobial susceptibility of 162 GBS colonizing and infective isolates recovered in Argentina. Serotypes Ia and III were the most prevalent ones, followed by Ib, II, V, IV and non-typeable. In relation to the 13 virulence genes screened, cpsA, cylE, hylB, lmb, and scpB were the most prevalent and could be postulated as vaccine epitopes; bca, rib, bac, hvgA, spb1, PI, PI-2a, and PI-2b were detected in lesser frequencies. No significant association was found between serotypes or virulence genes and colonizing or infective isolates but, on the contrary, significant association was observed between some genes and the most prevalent serotypes, la and III. The cluster analysis showed 52 virulence profiles and, antimicrobial resistance tests, 16 profiles, some with up to 4 resistances. Tetracycline resistance was significantly associated with colonizing isolates. Genes tetM and ermB conferring resistance to tetracyclines and macrolides, respectively, were the most commonly identified. Our findings show that GBS colonizing and infective isolates circulating in Argentina share similar features in terms of serotype and virulence genes and show a high level of antimicrobial resistance.