title: Selection and persistence of antimicrobial-resistant Escherichia coli including extended-spectrum β-lactamase producers in different poultry flocks on one chicken farm.
abstract: Escherichia coli isolates (n=438) from six different broiler chicken flocks (all in, all out) with known consumption of antimicrobials were investigated for their antimicrobial resistance and the prevalence of extended-spectrum β-lactamase (ESBL) phenotypes. E. coli were isolated from chicken at the third and fifth week of age and tested for antimicrobial resistance during the course of fattening. Resistance to sulfamethoxazole+trimethoprim, which was used in four flocks within the first days of life, decreased significantly in all six flocks between the third and fifth week of broiler chicken's life (mean 65.9% vs. 54.3%). By contrast, resistance to spectinomycin increased significantly in all six flocks within the same period (mean 36.1% vs. 57.0%); doxycycline resistance increased significantly in five of six flocks (mean 19.2% vs. 41.7%), although both substances were not used for treatment. Of the sulfonamide resistance genes sul1, sul2, and sul3, sul2 was most frequently found (up to 60%). The prevalence of sul2 increased significantly between weeks 3 and 5, if the chicken were treated with sulfamethoxazole + trimethoprim in the first days of life. If sulfamethoxazole + trimethoprim was not used, then the prevalence of sul2 decreased significantly in the same period. The prevalence of sul1+qacEΔ1 (classical class 1 integrons) was significantly higher in E. coli from sulfamethoxazole + trimethoprim-treated flocks (9.63%), compared to untreated flocks (2.92%). The detection of phenotypes that potentially indicate plasmid-borne AmpC-β-lactamases was inversely associated with sulfamethoxazole + trimethoprim treatment. ESBL phenotypes were found without selective enrichment in four of six flocks. Of all isolated E. coli, 1.8% (n=8) had an ESBL phenotype. ESBL strains differed in their accompanying resistances and/or enterobacterial repetitive intergenic consensus sequences. In conclusion, clonal dissemination seems not to be a major cause of ESBL detection on a chicken farm with all-in all-out production mode.
authors.affiliation: Chair of Animal Hygiene, WZW, Technische Universität München , Freising, Germany .
authors.forename: Karin
authors.initials: K
authors.lastname: Schwaiger
authors.forename: Johann
authors.initials: J
authors.lastname: Bauer
authors.forename: Christina Susanne
authors.initials: CS
authors.lastname: Hölzel
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002645:Chickens / Q000382:microbiology*; D021901:DNA, Intergenic; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D032023:Integrons; D010957:Plasmids; D011201:Poultry Diseases / Q000188:drug therapy / Q000382:microbiology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D000198:Spectinomycin / Q000494:pharmacology; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D021901:DNA, Intergenic; D029968:Escherichia coli Proteins; D020033:Protein Isoforms; C091882:Sul1 protein, E coli; D047090:beta-Lactams; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D000198:Spectinomycin; C048795:AmpC beta-lactamases; D001618:beta-Lactamases