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Investigation of the use of pooled faecal and environmental samples following an enrichment step for the detection of Salmonella enterica by real-time PCR
  1. N. Pusterla, DVM, PhD1,
  2. B. A. Byrne, DVM, PhD2,
  3. S. Mapes, MS1,
  4. N. Akana1,
  5. C. Wademan1,
  6. L. C. Fielding, DVM3,
  7. N. Slovis, DVM4,
  8. T. Elam4 and
  9. K. G. Magdesian, DVM1
  1. 1Department of Veterinary Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
  2. 2Department of Veterinary Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
  3. 3Loomis Basin Equine Medical Center, Penryn, CA 95663, USA
  4. 4Hagyard Equine Medical Institute, Lexington, KY 40511, USA
  1. E-mail for correspondence: npusterla{at}

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INFECTION with Salmonella enterica is an important cause of enteric disease and death in horses (Hartnack and others 2012). However, Salmonella can also be associated with subclinical shedding, representing a source of infection for other animals (Jones 2008). Estimates of the prevalence of Salmonella shedding in horses admitted to veterinary hospitals for elective procedures range from 1 per cent to 5 per cent (Smith and others 1978, Roberts and O'Boyle 1981, Pusterla and others 2010). Microbiologic culture of faeces, tissue, or body fluids is routinely used to detect horses infected with Salmonella. Clinical laboratories generally require at least 48 hours for presumptive detection of Salmonella in faeces with enrichment to detect small numbers of Salmonella. In recent years, PCR assays for the detection of Salmonella species in faecal samples from horses admitted to veterinary hospitals have been evaluated (Amavisit and others 2001, Kurowski and others 2002, Ward and others 2005, Pusterla and others 2010). Collectively, these studies have shown superior sensitivity of PCR when compared with microbiological culture. Although PCR has increased sensitivity and quicker turn-around-time, the costs associated with testing are generally higher than microbiological culture. This is especially true when environmental and faecal admission samples are tested for biosurveillance purposes, a practice used at many private and academic veterinary hospitals. In this situation, a sensitive and cost-effective test is needed to screen large numbers of samples. The purpose of this study was to evaluate the pooling of faeces and environmental samples following a selective enrichment culture step for the detection of Salmonella species by real-time PCR.

For the purpose of this study, 677 equine faecal (279 from VMTH/LBEMC; 398 from HEMI) and 686 environmental samples (420 VMTH/LBEMC, 266 HEMI) were examined. Faecal samples were collected from equine patients presenting to one of …

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