title: Resistance to third-generation cephalosporins in human non-typhoidal Salmonella enterica isolates from England and Wales, 2010-12.
abstract: OBJECTIVE
  To identify the mechanism(s) underlying cefotaxime resistance in 118 of 21,641 (0.55%) non-typhoidal Salmonella enterica isolates collected from humans throughout England and Wales from January 2010 to September 2012.
  
  
  METHODS
  Non-duplicate isolates (n = 118) resistant to cefotaxime (MICs >1 mg/L) were screened by PCR for genes encoding CTX-M extended-spectrum β-lactamases (ESBLs) and associated ISEcp1-like elements, and for genes encoding acquired AmpC, SHV, TEM, VEB, PER and GES β-lactamases. Sequencing was used to identify specific alleles in selected isolates. Carbapenem resistance was sought by ertapenem disc screening.
  
  
  RESULTS
  Seventy-nine isolates (0.37% of all referred S. enterica) produced ESBLs, 37 isolates (0.17%) produced CMY-type AmpC enzymes, and 1 isolate had both enzyme types; the mechanism of cefotaxime resistance in 3 isolates could not be identified. Group 1 CTX-M genes were identified in 57 isolates belonging to 22 serotypes, with CTX-M-1 (n = 11), -15 (n = 9) and -55/57 (n = 8) the most prevalent alleles among the 29 (51%) investigated. CTX-M-2 (n = 5), -14 (n = 5), -8 (n = 1) and -65 (n = 1) were also identified. TEM-52 was identified in two isolates and SHV-12 in seven isolates. There was no evidence of carbapenem resistance. ESBL and AmpC genes were detected in both domestically acquired and travel-associated salmonellae. Eighty-nine isolates (75%) were multidrug resistant (resistant to at least three antimicrobial classes) and 42 (36%) had decreased susceptibility to ciprofloxacin (MICs 0.25-1 mg/L), with a further 13 (11%) isolates resistant (MICs >1 mg/L).
  
  
  CONCLUSIONS
  The prevalence of CTX-M and acquired AmpC genes in human non-typhoidal S. enterica from England and Wales is still low, but has increased from 0.03% in 2001-03 to 0.49% in 2010-12. Resistance to third-generation cephalosporins requires monitoring as it may reduce therapeutic options.
authors.affiliation: Department of Clinical Microbiology, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland.
authors.forename: Liam
authors.initials: L
authors.lastname: Burke
authors.forename: Katie L
authors.initials: KL
authors.lastname: Hopkins
authors.forename: Daniele
authors.initials: D
authors.lastname: Meunier
authors.forename: Elizabeth
authors.initials: E
authors.lastname: de Pinna
authors.forename: Deirdre
authors.initials: D
authors.lastname: Fitzgerald-Hughes
authors.forename: Hilary
authors.initials: H
authors.lastname: Humphreys
authors.forename: Neil
authors.initials: N
authors.lastname: Woodford
mesh_terms: D000483:Alleles; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002439:Cefotaxime / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004739:England / Q000453:epidemiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D015995:Prevalence; D012480:Salmonella Infections / Q000453:epidemiology / Q000382:microbiology*; D012481:Salmonella Infections, Animal / Q000453:epidemiology / Q000382:microbiology*; D019779:Salmonella enterica / Q000187:drug effects* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D014852:Wales / Q000453:epidemiology; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002511:Cephalosporins; D004269:DNA, Bacterial; D001618:beta-Lactamases; D002439:Cefotaxime
keywords: AmpCs; ESBLs; surveillance