A rapid increase in macrolide resistance in Streptococcus pyogenes isolated in Poland during 1996-2002

Objectives: The aim of this study was to investigate Polish clinical isolates of Streptococcus pyogenes collected during a 7 year period using phenotypic and genotypic techniques. Methods: A total of 816 isolates of S. pyogenes recovered from 33 medical centres in Poland were tested for their susceptibility to various antimicrobial agents. Erythromycin-resistant isolates were analysed by PFGE, multilocus sequence typing and emm typing methods. Results: The tetracycline resistance rate was high (43%) among all S. pyogenes strains. Ninety-eight (12%) isolates were resistant to erythromycin. A low prevalence of the M phenotype (5.1%) associated with the presence of the mef(A) gene was found. All the isolates of the iMLS(B) phenotype harboured the erm(TR) gene. Out of the cMLS(B) isolates, 71.4% and 28.6% carried erm(TR) and erm(B), respectively. All isolates with erm(B) were resistant to telithromycin. PFGE analysis discerned 13 different patterns, A-N, with two predominant PFGE profiles-A (41 isolates) and B (25 isolates)-that in multilocus sequence typing corresponded, respectively, to a novel sequence type (ST) 367 and ST63. Overall, the representatives of these clones accounted for >90% of isolates of the iMLS(B) phenotype. Conclusions: A significant increase in erythromycin resistance was observed among clinical S. pyogenes collected in Poland over a 7 year period driven by the spread of two epidemic clones.