Prevalence and mechanisms of macrolide resistance in Streptococcus pyogenes in Ankara, Turkey

Abstract

From 2002 to 2003, a total of 381 consecutive S. pyogenes isolates were obtained from throat swabs (n = 337) and samples of pus (n = 31), sputum (n=10) and blood (n = 3) at Hacettepe University Hospital. The susceptibility of the isolates to erythromycin was tested by the agar dilution method. Erythromycin resistant strains were then tested for their MICs to azithromycin, clindamycin, and penicillin, their phenotype of resistance to macrolides-lincosamides-streptogramin B (MLS_B) and for the presence of macrolide resistance genes. The rate of resistance to erythromycin was 6.8%. Constitutive (cMLS_B), inducible (iMLS_B), and M phenotypes of resistance were detected in 7.7, 30.8, and 57.7% of resistant strains, respectively. One strain had both cMLS_B and iMLS_B phenotypes. All M phenotypes carried the mefA gene, all iMLS_B phenotype carried the ermTR gene, 1 isolate with cMLS_B phenotype harboured the ermB gene, and 1 isolate with cMLS_B phenotype carried both the ermB and mefA genes. One strain which showed cMLS_B and iMLS_B phenotypes harboured the ermB gene.