title: What causes decreased erythromycin resistance in Streptococcus pyogenes? Dynamics of four clones in a southern European region from 2005 to 2012.
abstract: OBJECTIVE
  To survey antibiotic resistance among Streptococcus pyogenes isolates collected from 2005 to 2012, to characterize those showing erythromycin resistance and to analyse the association of certain emm types with erythromycin resistance or susceptibility.
  
  
  METHODS
  Resistance determinants or mutations conferring erythromycin, clindamycin, tetracycline and fluoroquinolone resistance were analysed. All erythromycin-resistant isolates and a sample of erythromycin-susceptible isolates were emm typed. Multilocus sequence typing was performed for representative emm types.
  
  
  RESULTS
  Antimicrobial susceptibility was studied for 12 346 S. pyogenes isolates. Erythromycin, clindamycin and tetracycline resistance showed a decreasing trend. In 2012, 2.8% of isolates were erythromycin resistant versus 7.5% in 2005 and 11.7% in 2006. Although 21 clones were involved, 4 clones accounted for almost 90% of erythromycin-resistant isolates. The emm12/ST36 clone, carrying the mef(A) gene, was the predominant (41.1%) erythromycin-resistant clone, with an incidence peak in 2008, followed by a gradual decline. The M phenotype predominated each year except for 2005, when two of the main erythromycin-resistant clones (emm11/ST403 and emm28/ST52) harboured an erm(B) gene. Erythromycin resistance was significantly higher in adults than in children. Skin isolates showed the highest erythromycin resistance rate; among these, perianal isolates frequently belonged to the emm28/ST52 clone. The emm type was not a predictor of erythromycin resistance; however, most emm11 and emm12 were erythromycin-resistant isolates. Macrolide consumption was similar throughout the study period. Only two isolates with a high level of levofloxacin resistance were detected.
  
  
  CONCLUSIONS
  Resistance was mainly related to the circulation of emm12/ST36, emm11/ST403, emm28/ST52 and emm4/ST39 clones, all of which declined throughout the study period.
authors.affiliation: Microbiology Department, Hospital Universitario Donostia-Instituto Biodonostia, San Sebastián, Spain Biomedical Research Centre Network for Respiratory Diseases (CIBERES), San Sebastián, Spain.
authors.forename: Milagrosa
authors.initials: M
authors.lastname: Montes
authors.affiliation: Biomedical Research Centre Network for Respiratory Diseases (CIBERES), San Sebastián, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Tamayo
authors.affiliation: Microbiology Department, Hospital Universitario Donostia-Instituto Biodonostia, San Sebastián, Spain.
authors.forename: Catalina
authors.initials: C
authors.lastname: Mojica
authors.affiliation: Microbiology Department, Hospital Universitario Donostia-Instituto Biodonostia, San Sebastián, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: García-Arenzana
authors.affiliation: Biomedical Research Centre Network for Respiratory Diseases (CIBERES), San Sebastián, Spain.
authors.forename: Olatz
authors.initials: O
authors.lastname: Esnal
authors.affiliation: Microbiology Department, Hospital Universitario Donostia-Instituto Biodonostia, San Sebastián, Spain Biomedical Research Centre Network for Respiratory Diseases (CIBERES), San Sebastián, Spain Faculty of Medicine, University of the Basque Country, UPV/EHU, San Sebastián, Spain mikrobiol@terra.com.
authors.forename: Emilio
authors.initials: E
authors.lastname: Pérez-Trallero
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000942:Antigens, Bacterial / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004917:Erythromycin / Q000494:pharmacology*; D005060:Europe; D005838:Genotype; D049674:History, 21st Century; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D018942:Macrolides / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009154:Mutation; D010641:Phenotype; D013290:Streptococcal Infections / Q000453:epidemiology / Q000266:history / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D018942:Macrolides; C014689:streptococcal M protein; D004917:Erythromycin
keywords: MLST; emm types; erm(B) gene; mef(A) gene; mutation A2058G