DISTRIBUTION OF msr(D), mef(A/E), emm GENOTYPES AND VIRULENCE PROFILES AMONG BULGARIAN MACROLIDE RESISTANT STREPTOCOCCUS PYOGENES ISOLATES

Bulgaria has been one of the major macrolides consumers in Europe over the last years, which is linked to a dramatic raise in the resistance to these antimicrobials. This study aimed to investigate msr(D) presence among M phenotype positive Streptococcus pyogenes (group A-GAS) isolates, the association of the gene with emm types and different virulence factors. Seventy-nine clinical GAS isolates exhibiting the M phenotype resistance and 25 macrolide susceptible isolates were collected during 2016-2018 and were PCR tested for resistance genes: ermA/ermB, mef (A/E)-and mrs(D). For representative isolates, msr(D) was sequenced and emm type and twenty factors of virulence were determined. Student's t-test and Chi-square tests by SPSS V. 20 were used for statistical analysis. Co-existence of mef (A/E)/msr(D) was determined in all 79 tested isolates and all of them were ermA/ermB negative. The control group of 25 macrolide susceptible GAS strains did not harbour mef(A/E) and msr(D). The macrolide-nonsusceptible strains exhibited two resistotypes - one group with erythromycin MICs between 0.75-2 and the other - two isolates with 4 mg/L and 16 mg/L. Eleven emm genotypes were detected among mrs(D), positive isolates and among them, the most frequent were emm1 and emm4, with E1, E3 and A-C3 clusters. Twenty of 24 sequenced isolates possessed >= 5 virulence genes. The strains from El had >= 8 virulence factors. The strains with highest MICs had lower number of virulence genes compared with the other isolates. To our knowledge, this is the first detection of msr(D) in Bulgaria.