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Salmonella spp. are important food-borne pathogens that are demonstrating increasing antimicrobial resistance rates in isolates obtained from food animals and humans. In this study, 10 multidrug-resistant, cephalosporin-resistant Salmonella isolates from bovine, porcine, and human sources from a single geographic region were identified. All isolates demonstrated resistance to cephamycins and extended-spectrum cephalosporins as well as tetracycline, chloramphenicol, streptomycin, and sulfisoxazole. Molecular epidemiological analyses revealed eight distinct chromosomal DNA patterns, suggesting that clonal spread could not entirely explain the distribution of this antimicrobial resistance phenotype. However, all isolates encoded an AmpC-like beta-lactamase, CMY-2. Eight isolates contained a large nonconjugative plasmid that could transform Escherichia coli. Transformants coexpressed cephalosporin, tetracycline, chloramphenicol, streptomycin, and sulfisoxazole resistances. Plasmid DNA revealed highly related restriction fragments though plasmids appeared to have undergone some evolution over time. Multidrug-resistant, cephalosporin-resistant Salmonella spp. present significant therapeutic problems in animal and human health care and raise further questions about the association between antimicrobial resistance, antibiotic use in animals, and transfer of multidrug-resistant Salmonella spp. between animals and man.


Journal article


Antimicrob Agents Chemother

Publication Date





2777 - 2783


Animals, Animals, Domestic, Cephalosporin Resistance, DNA, Bacterial, Drug Resistance, Multiple, Electrophoresis, Gel, Pulsed-Field, Humans, Isoelectric Focusing, Microbial Sensitivity Tests, Molecular Epidemiology, Plasmids, Polymorphism, Restriction Fragment Length, Reverse Transcriptase Polymerase Chain Reaction, Salmonella, Salmonella Infections, Salmonella Infections, Animal, beta-Lactamases