Comparison of Salmonella enterica serotype Infantis isolates from a veterinary teaching hospital

Authors

  • M. Dunowska,

    1.  Animal Population Health Institute, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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  • P.S. Morley,

    1.  Animal Population Health Institute, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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  • J.L. Traub-Dargatz,

    1.  Animal Population Health Institute, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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  • M.A. Davis,

    1.  Department of Veterinary Microbiology and Pathology, Washington State, University, Pullman, WA, USA
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  • G. Patterson,

    1.  Animal Population Health Institute, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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  • J.G. Frye,

    1.  Bacterial Epidemiology and Antimicrobial Resistance Research Unit, U.S. Department of Agriculture, Agriculture Research Service, Athens, GA, USA
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  • D.R. Hyatt,

    1.  Animal Population Health Institute, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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  • D.A. Dargatz

    1.  Animal Population Health Institute, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
    2.  Centers for Epidemiology and Animal Health, USDA:APHIS:VS, 2150 Centre Avenue, Bldg B, Fort Collins, CO, USA
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  • Present address
    M. Dunowska, Unit 8, 69 Paxton Street, Denman 2328, Australia. G. Patterson, 4646 E. Mineral Rd., Phoenix, AZ, 85044, USA.

P.S. Morley, Animal Population Health Institute, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, 80523, USA.
E-mail: Paul.Morley@colostate.edu

Abstract

Aims:  To compare Salmonella enterica serotype Infantis isolates obtained from patients or the environment of a veterinary teaching hospital over a period of 9 years following a nosocomial outbreak to determine whether isolates were epidemiologically related or represented unrelated introductions into the hospital environment.

Methods and Results:  Fifty-six S. Infantis isolates were compared based on their phenotypic (antimicrobial drug [AMD] susceptibility pattern) and genotypic (pulsed-field gel electrophoresis [PFGE] pattern and presence of integrons) characteristics. Epidemiologically unrelated S. Infantis isolates clustered separately from all but two of the hospital isolates, and several isolates from different years and various sources were indistinguishable from each other in cluster analysis of two-enzyme PFGE results. A high percentage of isolates (80·3%) were resistant to at least one AMD, with 67·8% showing resistance to >5 AMD. The majority (74·1%) of isolates tested contained type 1 integrons.

Conclusion:  Results strongly suggest that there was nosocomial transmission of S. Infantis during the initial outbreak, and that contamination arising from this outbreak persisted across years despite rigorous hygiene and biosecurity precautions and may have led to subsequent nosocomial infections.

Significance and Impact of the Study:  Evidence of persistence and transmission of Salmonella clones across years, even in the face of rigorous preventive measures, has important implications for other facilities that have experienced outbreaks of Salmonella infections.

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