Erythromycin resistance genes in Streptococcus pyogenes isolates in Kanagawa, Japan

The susceptibility of 224 Streptococcus pyogenes isolates obtained from children in Japan from 1981 to 1997 to treatment with erythromycin was determined by the agar dilution method. A total of 17 isolates belonging to serotype M12T12 were resistant (MICs>1 microg/ml). Fourteen of the 17 resistant strains obtained from 1982 to 1985 harbored ermB and showed an identical pulsed-field gel electrophoresis pattern, indicating the spread of a single clone. Two ermTR-containing isolates were obtained in 1983. mefA gene was found in a strain obtained in 1994 in the present study, although this gene is predominantly associated with recent erythromycin resistance among S. pyogenes strains in many countries.