Prevalence and clonal characterization of Streptococcus pyogenes clinical isolates with reduced fluoroquinolone susceptibility in Spain.
The aim of this study was to determine the prevalence and characteristics of non-fluoroquinolone (FQ)-susceptible Streptococcus pyogenes isolates and to study their mechanisms of resistance. We performed a prospective prevalence study with 468 isolates collected from 2005 to 2007 and a retrospective study that was based on the examination of existing data collected from 1999 to 2008. The retrospective study included data for isolates with high-level resistance (HR) to ciprofloxacin (MIC >or= 32 microg/ml) (HR isolates) and isolates with the same emm types as those reported in the literature with low-level resistance (LR) to ciprofloxacin (MICs, 2 to 8 microg/ml) (LR isolates, n = 205). Genetic characterization of the isolates was performed by means of emm typing and multilocus sequence typing. The prevalence of LR ranged from 1.9% in 2005 to 30.8% in 2007. This increase was mainly due to the circulation of an emm6 subtype (emm6.4) that represented 77.1% of the LR isolates in 2007. Notably, another emm6 subtype, also detected in 2007 (emm6.37), showed coresistance to 14- and 15-membered macrolides mediated by the mefA gene. Only three HR isolates were detected (isolates emm68.1/ST247/T3,13,B3264, emm77/ST399/T28, and emm28/ST52/T28), and all were identified in the retrospective study. Overall, the 673 isolates represented 25 emm types. All LR isolates were clustered into two emm types: emm6 (six emm6 subtypes) and emm75. All the 156 emm6 isolates had LR, harbored the Ser79/Ala mutation in the parC gene product, and had the same sequence type (ST), ST382. Most (21/33) of the emm75 isolates had LR, showed the Ser79/Phe plus Asp91/Asn double mutation in the parC gene product, and were ST150. The Asp91/Asn mutation by itself did not confer resistance to FQs.
Montes
Milagrosa
M
Centro de Investigación Biomédica en Red Enfermedades Respiratorias (CIBERES), San Sebastian, Spain.
Tamayo
Esther
E
Orden
Beatriz
B
Larruskain
Julián
J
Perez-Trallero
Emilio
E
D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002648:Child; D024881:Drug Resistance, Bacterial; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology* / Q000627:therapeutic use; D005798:Genes, Bacterial; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D009154:Mutation / Q000235:genetics; D011446:Prospective Studies; D013030:Spain / Q000453:epidemiology; D013290:Streptococcal Infections / Q000453:epidemiology* / Q000209:etiology / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000235:genetics
D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones