ANTIMICROBIAL SUSCEPTIBILITY OF STREPTOCO CCUS-PYOGENES STRAINS ISOLATED IN 1986 AND IN 1994-1995

Background: The frequency of Streptococcus pyogenes infections with de ep tissue invasion and toxic shock syndrome has increased in the last decade throughout the world. Aim: To compare antimicrobial susceptibil ity of S. pyogenes strains isolated during 1986 and during 1994-95. Ma terial and method. Eighty two S. pyogenes strains isolated in 1986 and 67 strains isolated in 1994-95, were studied. MIC 50 and 90 were dete rmined by and agar dilution method for penicillin, ampicillin, cefazol in, cefuroxine, erythromycin, roxithromycin and miocamycin. Results: E ighty eight strains came from skin of soft tissues, 19 from surgical w ounds, 18 from invasive infections, 15 from pharyngeal swabs and 9 fro m other locations. All strains were susceptible to penicillin, ampicil lin, cefazolin, cefuroxime, roxithromycin and miocamycin. Ninety nine percent of strains were susceptible to erythromycin. Strains isolated in 1995-95 had a higher MIC 50 and 90 for erythromycin than those isol ated in 1986. Conclusions: The changes in susceptibility to erythromyc in of recently isolated strains could be due to the widespread use of macrolides in Chile.