Evaluation of a PCR to detect Salmonella in fecal samples of horses admitted to a veterinary teaching hospital.

This research is about the evaluation of a PCR test for detecting Salmonella in horses’ feces, specifically in comparison to traditional bacterial culture methods. The study ultimately found that the PCR test showed significant agreement with the bacterial culture method, but further research is needed for it to become a standard part of Salmonella surveillance for hospitalized horses.

Objectives of the Research

• The major objective of the study was to evaluate the accuracy of a polymerase chain reaction (PCR) test for identifying horses shedding Salmonella in their feces during hospitalization. The researchers compared the PCR test with bacterial culture methods.
• Another aim was to determine if the PCR method could be incorporated into Salmonella surveillance programs for hospitalized equine populations, thereby improving the detection and control of the bacteria in these settings.

Methodology

• The researchers collected five or more fecal samples from each of 116 horses that were admitted as inpatients to a veterinary hospital for reasons other than gastrointestinal disease.
• All 873 fecal samples collected were then tested with a PCR method that focused on a highly conserved segment of the histidine transport operon gene of Salmonella typhimurium. Each sample was also cultured for Salmonella for comparison purposes.

Results

• One or more samples from 87 (75%) horses were PCR positive, whereas Salmonella was cultured from one or more samples from 11 (9.5%) horses.
• All culture-positive horses had at least one PCR-positive result, implying that the PCR test had a high specificity when compared to the bacterial culture methods.
• However, only 29 (28%) culture-negative horses were PCR negative on all fecal samples tested, indicating a potential for false positives in the PCR test.
• The researchers found the greatest agreement (70%) between PCR and bacterial culture methods when they defined a Salmonella-positive horse as one that had two or more positive PCR test results.

Conclusion

• Though the PCR test proved useful in detecting Salmonella in horse feces, the researchers suggest that more research is needed to understand why some fecal samples, from which Salmonella organisms cannot be isolated, are PCR positive. This further exploration is necessary before incorporating the PCR test into Salmanella surveillance programs for hospitalized equines.