Phenotypic and genotypic characterization of macrolide-resistant group A Streptococcus strains in the province of Quebec, Canada

Resistance to macrolides among group A streptococci is an increasing proble m worldwide. We examined 496 strains phenotypically and genotypically for r esistance to erythromycin and clindamycin. Strains were isolated in five di fferent geographical areas representing about 45% of the total Quebec popul ation. The overall resistance rate was 4.6% but varied from 0% in rural are as to 9.4% in Montreal. Of the 23 strains showing resistance to erythromyci n, 15 (65%) had an identical pulsed-field gel electrophoresis pattern, were of serotype M28T28 and harboured the erm(TR) gene, suggesting the spread o f a single clone. Of the remaining eight strains, two strains had the erm(B ) gene, five had the mef gene and one with a different serotype also had th e erm(TR) gene.