RESUMO
The frequency of Streptococcus pyogenes infections with deep tissue and toxic shock syndrome has increased in the last decade throughout the world. Aim: to compare antimicrobial susceptibility of S. pyogenes strains isolated during 1986 and 1994-95. Eighty two S. pyogenes strains isolated in 1986 and 67 strains isolated in 1994-1995, were studied. MIC 50 and 90 were determined by an agar dilution method for penicillin, ampicillin, cefazolin, cefuroxime, erythromicin. roxithromycin and miocamycin. Eighty eight strains came from skin of soft tissues, 19 from surgical wounds, 18 from invasive infections, 15 from pharyngeal swabs and 9 from other locations. All strains were susceptible to penicillin, ampicillin, cefazolin, cefuroxime, roxithromycin and miocamycin. Ninety nine percent of strains were susceptibel to erythromycin. Strains isolated in 1994-95 had a higher MIC 50 and 90 for erythromycin than those isolated in 1986. The changes in susceptibility to erythromycin of recently isolated strains could be due to the widespread use of macrolides in Chile