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Journal of Veterinary Medicine
Volume 2016, Article ID 6380890, 8 pages
http://dx.doi.org/10.1155/2016/6380890
Research Article

Phenotypic and Genotypic Characterization of Animal-Source Salmonella Heidelberg Isolates

1California Animal Health & Food Safety Lab System, School of Veterinary Medicine, University of California, Davis, Davis, CA 95616, USA
2Departments of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, CA 95616, USA
3Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, Davis, CA 95616, USA

Received 25 August 2015; Accepted 7 December 2015

Academic Editor: Antonio Ortega-Pacheco

Copyright © 2016 Kristin A. Clothier and Barbara A. Byrne. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Salmonella enterica serotype Heidelberg (S. Heidelberg) is frequently implicated in human foodborne Salmonella infections and often produces more severe clinical disease than other serotypes. Livestock and poultry products represent a potential risk for transmission to humans. The purpose of this study was to evaluate 49 S. Heidelberg veterinary isolates for exponential growth rate (EGR), PFGE pattern, and antimicrobial resistance to evaluate these parameters as mechanisms by which S. Heidelberg emerged as a virulent foodborne pathogen. Isolates were categorized by species of origin; clinical or environmental sources; and time frame of recovery. Growth rates were determined in nutrient media using serial dilutions and colony counts; PFGE was performed according to the CDC PulseNet protocol. Minimum inhibitory concentration and susceptibility determinations were performed against antimicrobials important in human medicine. Eighteen unique PFGE patterns were detected in the isolates tested. Antimicrobial resistance was significantly greater () for ten of 15 drugs in clinical over environmental isolates; for four drugs between the time frames; and for ten drugs between species of origin. The large genetic diversity present in isolates of this serotype may convey competitive advantages to this organism, while the presence of antimicrobial resistance represents a potential zoonotic risk via animal-source food products.