title: Streptococcus pyogenes isolates with characterized macrolide resistance mechanisms in Spain: in vitro activities of telithromycin and cethromycin.
abstract: The in vitro activities of telithromycin and cethromycin (ABT-773) against 412 Streptococcus pyogenes isolates, consecutively collected in 17 Spanish hospitals from different geographical areas, were evaluated and compared with those of erythromycin A, penicillin G, clindamycin and quinupristin-dalfopristin. With a susceptibility testing breakpoint of < or = 1 mg/L for both compounds, 96.1% of isolates were susceptible to telithromycin and 99.8% to cethromycin. Erythromycin non-susceptible isolates (intermediate plus resistant, MIC > or = 0.5 mg/L) comprised 23% of those tested, and were analysed for the genetic basis of their resistance by PCR. Among these isolates (n = 95), 72.6% harboured mef(A), 8.4%, erm(B), and 3.2%, erm(A), as sole macrolide resistance gene, whereas the presence of mef(A) plus erm(A) (11.6%) or mef(A) plus erm(B) (4.2%) was also observed. Both ketolides displayed a significant in vitro activity against S. pyogenes regardless of the macrolide resistance mechanisms. Nevertheless, in the case of telithromycin, 11 out of 19 of the erm(B)-positive isolates (2.7% of total population) exhibited an MIC range of 4-32 mg/L. According to the present results, telithromycin and cethromycin offer a wide coverage against S. pyogenes isolates in a geographic area with a high incidence of resistance to currently used macrolides.
authors.affiliation: Servicio de Microbiología, Hospital Universitario Ramón y Cajal, Ctra. de Colmenar, Km 9,1, 28034 Madrid, Spain.
authors.forename: María-Isabel
authors.initials: MI
authors.lastname: Morosini
authors.forename: Rafael
authors.initials: R
authors.lastname: Cantón
authors.forename: Elena
authors.initials: E
authors.lastname: Loza
authors.forename: Rosa
authors.initials: R
authors.lastname: del Campo
authors.forename: Felisa
authors.initials: F
authors.lastname: Almaraz
authors.forename: Fernando
authors.initials: F
authors.lastname: Baquero
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004351:Drug Resistance; D004917:Erythromycin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D005798:Genes, Bacterial / Q000235:genetics; D006801:Humans; D048628:Ketolides; D018942:Macrolides; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013030:Spain; D013290:Streptococcal Infections / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D048628:Ketolides; D018942:Macrolides; D004917:Erythromycin; C405499:cethromycin; C106791:telithromycin