Table 2.

Distribution of erythromycin resistance genes among 45 erythromycin-resistant S. pyogenes isolates, including 19 M-phenotype isolates, 24 IR-phenotype isolates, and 2 CR-phenotype isolates

Erythromycin resistance phenotype and T-antigen typeNo. of isolates testedPresence of the following gene:
mefAermAermBermCermTR
M
 4+12a +
 Nontypeable+6+
 13/B3264−1+
IR
 28+19b +
 9+2+
 5/27/44+1+
 9−1+
 28−1+
CR
 4−1+
 28+1+
  • a Eight of 12 isolates were shown to be of different clonal origin by randomly amplified polymorphic DNA analysis.

  • b Isolates of different geographical origins.