Prevalence and Mechanisms of Macrolide Resistance in Streptococcus pyogenes in Santiago, Chile

Thirty-two macrolide-resistant Streptococcus pyogenes isolates were found among 594 clinical isolates collected from 1990 to 1998 in Santiago, Chile, for an overall prevalence of 7.2%. Among the 32 resistant isolates, 28 (87.5%) presented the M phenotype and 4 (12.5%) presented the MLS(B) phenotype. Serotyping and pulsed-field gel electrophoresis analysis showed genetic diversity among the resistant isolates.