title: Activity of ceftibuten, cefaclor, azithromycin, clarithromycin, erythromycin and telithromycin against Streptococcus pyogenes clinical isolates with different genotypes and phenotypes.
abstract: BACKGROUND
  The growing number of macrolide-resistant strains of Streptococcus pyogenes represents an increasing worldwide problem. Macrolide resistance in S. pyogenes is mediated by several different genes, which determine different levels of resistance to macrolides, lincosamides and streptogramin B (MLS).
  
  
  METHODS
  This study compared the in vitro antimicrobial activity of azithromycin, clarithromycin, erythromycin, ceftibuten, cefaclor, and telithromycin against 287 strains of S. pyogenes by the broth microdilution method. All strains were characterized both phenotypically and genotypically for erythromycin resistance and most of them have been M-typed by means of PCR.
  
  
  RESULTS
  Ceftibuten and cefaclor showed the best antimicrobial activity, while MIC values for telithromycin were higher against constitutively MLS (cMLS)-resistant strains rather than against the other phenotypes.
  
  
  CONCLUSIONS
  Oral cephalosporins retain the best activity against S. pyogenes; showing good activity except for cMLS-resistant strains, telithromycin is a valid alternative to these antimicrobials.
authors.affiliation: Department of Molecular Cellular Animal Biology, University of Camerino, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Drago
authors.forename: Sandro
authors.initials: S
authors.lastname: Ripa
authors.forename: Claudia
authors.initials: C
authors.lastname: Zampaloni
authors.forename: Elena
authors.initials: E
authors.lastname: De Vecchi
authors.forename: Luca A
authors.initials: LA
authors.lastname: Vitali
authors.forename: Dezemona
authors.initials: D
authors.lastname: Petrelli
authors.forename: Manuela
authors.initials: M
authors.lastname: Prenna
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002648:Child; D024881:Drug Resistance, Bacterial; D005838:Genotype; D006801:Humans; D018942:Macrolides / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D013290:Streptococcal Infections / Q000188:drug therapy; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D018942:Macrolides