title: Characterization of multidrug-resistant Escherichia coli isolates from animals presenting at a university veterinary hospital.
abstract: In this study, we examined molecular mechanisms associated with multidrug resistance (MDR) in a collection of Escherichia coli isolates recovered from hospitalized animals in Ireland. PCR and DNA sequencing were used to identify genes associated with resistance. Class 1 integrons were prevalent (94.6%) and contained gene cassettes recognized previously and implicated mainly in resistance to aminoglycosides, β-lactams, and trimethoprim (aadA1, dfrA1-aadA1, dfrA17-aadA5, dfrA12-orfF-aadA2, bla(OXA-30)-aadA1, aacC1-orf1-orf2-aadA1, dfr7). Class 2 integrons (13.5%) contained the dfrA1-sat1-aadA1 gene array. The most frequently occurring phenotypes included resistance to ampicillin (97.3%), chloramphenicol (75.4%), florfenicol (40.5%), gentamicin (54%), neomycin (43.2%), streptomycin (97.3%), sulfonamide (98.6%), and tetracycline (100%). The associated resistance determinants detected included bla(TEM), cat, floR, aadB, aphA1, strA-strB, sul2, and tet(B), respectively. The bla(CTX-M-2) gene, encoding an extended-spectrum β-lactamase (ESβL), and bla(CMY-2), encoding an AmpC-like enzyme, were identified in 8 and 18 isolates, respectively. The mobility of the resistance genes was demonstrated using conjugation assays with a representative selection of isolates. High-molecular-weight plasmids were found to be responsible for resistance to multiple antimicrobial compounds. The study demonstrated that animal-associated commensal E. coli isolates possess a diverse repertoire of transferable genetic determinants. Emergence of ESβLs and AmpC-like enzymes is particularly significant. To our knowledge, the bla(CTX-M-2) gene has not previously been reported in Ireland.
authors.affiliation: UCD Centre for Food Safety & Centre for Food-borne Zoonomics, UCD Veterinary Sciences Centre, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Maria
authors.initials: M
authors.lastname: Karczmarczyk
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Abbott
authors.forename: Ciara
authors.initials: C
authors.lastname: Walsh
authors.forename: Nola
authors.initials: N
authors.lastname: Leonard
authors.forename: Séamus
authors.initials: S
authors.lastname: Fanning
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D006762:Hospitals, Animal; D032023:Integrons; D007494:Ireland; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014495:Universities
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial