title: Susceptibility to disinfectants in antimicrobial-resistant and -susceptible isolates of Escherichia coli, Enterococcus faecalis and Enterococcus faecium from poultry-ESBL/AmpC-phenotype of E. coli is not associated with resistance to a quaternary ammonium compound, DDAC.
abstract: OBJECTIVE
  The spread of bacteria that are simultaneously resistant to disinfectants and antimicrobials would constitute an unsettling scenario. In order to explore an association between antimicrobial resistance and reduced susceptibility to biocides/microbicides (disinfectants) in agriculture, we investigated Escherichia coli (n = 438) and enterococci (n = 120) isolated from six different flocks of the same poultry farm with known history of antimicrobial treatment.
  
  
  RESULTS
  Susceptibility to disinfectants (formic acid and a quaternary ammonium compound (QAC), didecyldimethylammoniumchloride-DDAC) was assessed by macrodilution according to guidelines of the German Veterinary Society. Escherichia coli, Enterococcus faecalis and Enterococcus faecium were screened (i) for reduced biocide susceptibility and (ii) for an association of biocide susceptibility and antimicrobial resistance including the production of extended-spectrum beta-lactamases (ESBL) and the hyperproduction of AmpC-type beta-lactamases. DDAC inhibited ESBL/AmpC(hyper)-producing E. coli (n = 53) from poultry at similar or slightly lower inhibitory concentrations, compared with non-ESBL/AmpC strains (median MIC = 0·36 vs 1·44 mg l-1). In contrast, DDAC-MICs were positively correlated with several other antibiotic MICs (e.g. piperacillin and sulphamethoxazole + trimethoprim in E. coli, chloramphenicol in E. faecalis) and increased DDAC-MICs were statistically linked to high-level aminoglycoside resistance in enterococci (streptomycin high level). DDAC-MICs did not correlate with the presence of the integron marker qacEDelta1.
  
  
  CONCLUSIONS
  This study provides indication that residual disinfectant might be able to select antimicrobial-resistant enterococci, but not ESBL-/AmpC (hyper)producing E. coli from poultry.
  
  
  CONCLUSIONS
  While ESBL-/AmpC-E. coli were inhibited at disinfectant concentrations comparable to or lower than wildtype values, low concentrations of QACs might be able to select other antimicrobial-resistant E. coli or enterococci-a finding with special significance for the food processing industry, where QACs are regularly used.
authors.affiliation: Chair of Animal Hygiene, WZW, TUM, Freising, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Wieland
authors.affiliation: Bavarian Health and Food Safety Authority (LGL), Oberschleißheim, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Boss
authors.affiliation: Department of Veterinary Sciences, Faculty of Veterinary Medicine, LMU, München, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Lettmann
authors.affiliation: Department of Veterinary Sciences, Faculty of Veterinary Medicine, LMU, München, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Fritz
authors.affiliation: Department of Veterinary Sciences, Faculty of Veterinary Medicine, LMU, München, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Schwaiger
authors.affiliation: Chair of Animal Hygiene, WZW, TUM, Freising, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Bauer
authors.affiliation: Department of Veterinary Sciences, Faculty of Veterinary Medicine, LMU, München, Germany.
authors.forename: C S
authors.initials: CS
authors.lastname: Hölzel
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D004202:Disinfectants / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism; D016984:Enterococcus faecium / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D011200:Poultry / Q000382:microbiology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004202:Disinfectants; D000644:Quaternary Ammonium Compounds; C053645:N,N-dimethyl-N-hexadecyl-1-octadecylammonium; C048795:AmpC beta-lactamases; D001618:beta-Lactamases
keywords: 
  DDAC
  ; 
  E. coli
  ; 
  ESBL
  ; antimicrobial resistance; biocides; disinfectant; enterococci; livestock; poultry; quaternary ammonium compound = QAC