Molecular epidemiology and distribution of serotypes, genotypes, and antibiotic resistance genes of Streptococcus agalactiae clinical isolates from Guelma, Algeria and Marseille, France

Abstract

This study describes, for the first time, the genetic and phenotypic diversity among 93 Streptococcus agalactiae (group B Streptococcus, GBS) isolates collected from Guelma, Algeria and Marseille, France. All strains were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The molecular support of antibiotic resistance and serotyping were investigated by polymerase chain reaction (PCR). The phylogenetic lineage of each GBS isolate was determined by multilocus sequence typing (MLST) and grouped into clonal complexes (CCs) using eBURST. The isolates represented 37 sequence types (STs), 16 of which were novel, grouped into five CCs, and belonging to seven serotypes. Serotype V was the most prevalent serotype in our collection (44.1 %). GBS isolates of each serotype were distributed among multiple CCs, including cps III/CC19, cps V/CC1, cps Ia/CC23, cps II/CC10, and cps III/CC17. All isolates presented susceptibility to penicillin, whereas resistance to erythromycin was detected in 40 % and tetracycline in 82.2 % of isolates. Of the 37 erythromycin-resistant isolates, 75.7 % showed the macrolide–lincosamide–streptogramin B (MLSB)-resistant phenotype and 24.3 % exhibited the macrolide (M)-resistant phenotype. Constitutive MLSB resistance (46 %) mediated by the ermB gene was significantly associated with the Guelma isolates, whereas the M resistance phenotype (24.3 %) mediated by the mefA/E gene dominated among the Marseille isolates and belonged to ST-23. Tetracycline resistance was predominantly due to tetM, which was detected alone (95.1 %) or associated with tetO (3.7 %). These results provide epidemiological data in these regions that establish a basis for monitoring increased resistance to erythromycin and also provide insight into correlations among clones, serotypes, and resistance genes.