Characterization of Multidrug-ResistantEscherichia coliIsolates Associated with Nosocomial Infections in Dogs

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Abstract
Multidrug-resistant opportunistic pathogens have become endemic to the veterinary hospital environment.Escherichia coliisolates resistant to 12 antibiotics were isolated from two dogs that were housed in the intensive care unit at The University of Georgia Veterinary Teaching Hospital within 48 h of each other. Review of 21 retrospective and prospective hospital-acquiredE. coliinfections revealed that the isolates had similar antibiotic resistance profiles, characterized by resistance to most cephalosporins, β-lactams, and the β-lactamase inhibitor clavulanic acid as well as resistance to tetracycline, spectinomycin, sulfonamides, chloramphenicol, and gentamicin.E. coliisolates with similar resistance profiles were also isolated from the environment in the intensive care unit and surgery wards. MultipleE. coligenetic types were endemic to the hospital environment, with the pulsed-field gel electrophoresis fingerprint identified amongE. coliisolates from diseased animals and the hospital environment matching. The extended-spectrum cephalosporin resistance in these nosocomialE. coliisolates was attributed to the cephamycinase-encoding gene,blaCMY2. Chloramphenicol resistance was due in part to the dissemination of the florfenicol resistance gene,flo, among these isolates. Resistance encoded by both genes was self-transmissible. AlthoughblaCMY2andflowere common to the polyclonal, nosocomialE. coliisolates, there was considerable diversity in the genetic compositions of class 1 integrons, especially among isolates belonging to the same genetic type. Two or more integrons were generally present in these isolates. The gene cassettes present within each integron ranged in size from 0.6 to 2.4 kb, although a 1.7-kb gene cassette was the most prevalent. The 1.7-kb gene cassette contained spectinomycin resistance geneaadA5and trimethoprim resistance genedfrA17.

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