title: Erythromycin resistance of Streptococcus pyogenes in Madrid.
abstract: BACKGROUND
  Erythromycin is considered to be an adequate alternative to penicillin for patients who are allergic to penicillin. Erythromycin-resistant Streptococcus pyogenes strains have been reported in some parts of the world.
  
  
  METHODS
  The in vitro activity of erythromycin and other antimicrobial agents was determined in a total of 1310 clinical Streptococcus pyogenes isolates collected in the city of Madrid from January, 1993, through December, 1996.
  
  
  RESULTS
  All strains showed susceptibility to penicillin, rifampin, vancomycin and chloramphenicol. Tetracycline resistance was 8.5%. In 36 of the strains (2.7%) MIC was 4 microg/ml for ofloxacin. Clindamycin resistance was observed in only 18 strains (1.4%); this resistance was constitutive in 15 and inducible in 3 strains. Resistance to erythromycin was observed in 14.3% of the strains, showing an increase during the study period (2.0% in 1993 vs. 22.4% in 1996; chi square for linear trend 68.8, P < 0,0001); >90% of them showed the novel resistance phenotype described by Seppälä et al. and 32 of 32 of these strains showed by PCR the 1.4-kb fragment of the mefA gene recently described as the novel macrolide efflux resistance determinant. The erythromycin-resistant strains were isolated more often in pediatric patients (144 of 872) than in adults (44 of 438) (chi square 9.9, P = 0.0016).
  
  
  CONCLUSIONS
  The study emphasizes the need to screen for resistance to macrolides in S. pyogenes and indicates that resistance to erythromycin in S. pyogenes has increased significantly in Madrid.
authors.affiliation: Laboratorio, Centro Especialidades Argüelles, Madrid, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Orden
authors.forename: E
authors.initials: E
authors.lastname: Perez-Trallero
authors.forename: M
authors.initials: M
authors.lastname: Montes
authors.forename: R
authors.initials: R
authors.lastname: Martínez
mesh_terms: D000293:Adolescent; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D004352:Drug Resistance, Microbial; D004917:Erythromycin / Q000494:pharmacology* / Q000627:therapeutic use; D005798:Genes, Bacterial; D006801:Humans; D007223:Infant; D008826:Microbial Sensitivity Tests; D013030:Spain; D013290:Streptococcal Infections / Q000188:drug therapy*; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D004917:Erythromycin