Recovery of Salmonella bacterial isolates from pooled fecal samples from horses.

This research study assesses the efficacy of pooled fecal sample testing for the detection of Salmonella in horses. It concluded that pooling of 5 fecal samples is a sensitive and cost-effective method for detecting whether a horse is shedding the bacteria.

Research Objectives

The objective of the research was twofold:

• To determine the best pooling technique for maintaining a high sensitivity of culture for Salmonella, by using spiked samples.
• To demonstrate the effectiveness of this protocol with clinical submissions.

The underlying hypothesis was that pooled fecal samples are as sensitive as 5 individual cultures for detecting Salmonella shedding.

Methods

The research study was conducted using one Salmonella-negative horse from the university herd and nineteen hospitalized horses. The researchers used fecal samples that were free from Salmonella, which were then spiked with different concentrations of the bacteria. The samples were homogenized to evaluate the sensitivity of pooled samples. The researchers then collected five individual fecal samples from each of the 19 hospitalized horses. These samples were combined to create a pooled sample, and both the individual and pooled samples were cultured for Salmonella.

The bacteria identified were then confirmed through matrix-assisted laser desorption-ionization time of flight mass spectrometry, a technique that can accurately identify bacterial species.

Results

Analysis of the spiked fecal samples revealed that a concentration of 10 cfu of Salmonella could be successfully recovered from a spiked sample. The researchers learned that adding 20mL of broth to the pooled sample enhanced recovery, whereas the homogenization time did not have a significant effect. Five out of the nineteen horses tested positive for Salmonella. In every case, the bacteria were recovered from both the pooled sample and the individual samples.

Conclusions

The result of the research suggested that carrying out a Salmonella culture on a pool of five fecal samples is a sensitive and cost-effective approach for detecting horses that are shedding the bacteria. Therefore, this technique of pooling feces from multiple animals could serve as a more efficient and less costly means of Salmonella testing in equine populations.