title: Molecular characteristics of extended-spectrum cephalosporin-resistant Enterobacteriaceae from humans in the community.
abstract: OBJECTIVE
  To investigate the molecular characteristics of extended-spectrum cephalosporin (ESC)-resistant Enterobacteriaceae collected during a cross-sectional study examining the prevalence and risk factors for faecal carriage of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in humans living in areas with high or low broiler density.
  
  
  METHODS
  ESC-resistant Enterobacteriaceae were identified by combination disc-diffusion test. ESBL/AmpC/carbapenemase genes were analysed using PCR and sequencing. For E. coli, phylogenetic groups and MLST were determined. Plasmids were characterized by transformation and PCR-based replicon typing. Subtyping of plasmids was done by plasmid multilocus sequence typing.
  
  
  RESULTS
  175 ESC-resistant Enterobacteriaceae were cultured from 165/1,033 individuals. The isolates were Escherichia coli(n=65), Citrobacter freundii (n=52), Enterobacter cloacae (n=38), Morganella morganii (n=5), Enterobacter aerogenes (n=4), Klebsiella pneumoniae (n=3), Hafnia alvei (n=2), Shigella spp. (n=2), Citrobacter amalonaticus (n=1), Escherichia hermannii (n=1), Kluyvera cryocrescens (n=1), and Pantoea agglomerans (n=1). The following ESBL genes were recovered in 55 isolates originating from 49 of 1,033 (4.7 %) persons: blaCTX-M-1 (n=17), blaCTX-M-15 (n=16), blaCTX-M-14 (n=9), blaCTX-M-2 (n=3), blaCTX-M-3 (n=2), blaCTX-M-24 (n=2), blaCTX-M-27 (n=1), blaCTX-M-32 (n=1), blaSHV-12 (n=2), blaSHV-65 (n=1) and blaTEM-52 (n=1). Plasmidic AmpC (pAmpC) genes were discovered in 6 out of 1,033 (0.6 %) persons. One person carried two different E. coli isolates, one with blaCTX-M-1 and the other with blaCMY-2 and therefore the prevalence of persons carrying Enterobacteriaceae harboring ESBL and/or pAmpC genes was 5.2 %. In eight E. coli isolates the AmpC phenotype was caused by mutations in the AmpC promoter region. No carbapenemase genes were identified. A large variety of E. coli genotypes was found, ST131 and ST10 being most common.
  
  
  CONCLUSIONS
  ESBL/pAmpC genes resembled those from patients in Dutch hospitals, indicating that healthy humans form a reservoir for transmission of these determinants to vulnerable people. The role of poultry in the transmission to humans in the community remains to be elucidated.
authors.affiliation: Centre for Infectious Disease Control (CIb), National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
authors.forename: Angela H A M
authors.initials: AH
authors.lastname: van Hoek
authors.affiliation: Centre for Infectious Disease Control (CIb), National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
authors.forename: Leo
authors.initials: L
authors.lastname: Schouls
authors.affiliation: Centre for Infectious Disease Control (CIb), National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
authors.forename: Marga G
authors.initials: MG
authors.lastname: van Santen
authors.affiliation: Centre for Infectious Disease Control (CIb), National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
authors.forename: Alice
authors.initials: A
authors.lastname: Florijn
authors.affiliation: Centre for Infectious Disease Control (CIb), National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
authors.forename: Sabine C
authors.initials: SC
authors.lastname: de Greeff
authors.affiliation: Centre for Infectious Disease Control (CIb), National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
authors.forename: Engeline
authors.initials: E
authors.lastname: van Duijkeren
mesh_terms: D000328:Adult; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D002511:Cephalosporins / Q000494:pharmacology*; D002645:Chickens / Q000235:genetics; D003430:Cross-Sectional Studies; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004755:Enterobacteriaceae / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D005243:Feces / Q000737:chemistry / Q000382:microbiology*; D006801:Humans; D058885:Multilocus Sequence Typing / Q000379:methods; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002511:Cephalosporins; C048795:AmpC beta-lactamases; D001618:beta-Lactamases