Institution: University of Georgia
Principal Investigator:
Dr. Nikki W. Shariat, Ph.D.
University of Georgia
Poultry Diagnostic and Research Center
953 College Station Road
Athens, GA 30602
| Accurate and rapid surveillance for Salmonella is required as a key step in assessing whether mitigation strategies are effective in poultry flocks. The gold standard for Salmonella detection on broiler carcasses is a culture-based protocol that includes several steps and takes multiple days to complete. Traditional Salmonella isolation at a minimum takes 4-5 days and reducing this time may be beneficial. Limitations of the culture-based protocol include: (1) only the most abundant serotypes are detected and those in the minority remain ‘masked’, and (2) selective enrichment introduces bias and some serovars may outcompete others. Salmonella in live production often exists in mixed serotype populations. These mixed populations are not realized when only 1-2 colonies are picked off a plate for surveillance, as is done for Salmonella monitoring in pre- and post-harvest poultry. Therefore, it is a challenge to assess the complexity of serotypes entering the processing plant and, subsequently, which serotypes are able to persist on a carcass through different processing interventions.
The two objectives of this project were to (1) Improve Salmonella surveillance by addressing limitations in conventional culture detection, and (2) More accurately trace Salmonella serotype populations at a commercial poultry processing plant using CRISPR-SeroSeq. To accomplish the first objective, the researcher traced Salmonella serotypes at a commercial plant to determine the serotype profiles after each major processing step by sampling carcasses, at both at pre- and post-chill, plus parts. To accomplish the second objective, the researcher investigated biases introduced in conventional enrichment by comparing pre-enriched and enriched serotype profiles from multiple poultry-related matrices (e.g., carcasses, broiler house, litter, feed). Findings for objective 1 demonstrated that partially increasing the selectivity of the non-selective pre-enrichment culture step was sufficient to recover Salmonella 24 hours earlier than is the current standard using selective enrichments. This approach yielded similar Salmonella prevalence compared to the traditional two-step culture approach. During objective 2 experiments, Salmonella incidence was low post intervention, so the researcher expanded the sampling strategy significantly. Eighteen different visits were conducted across three processing facilities where samples were collected in duplicate at each visit (one set per processing line). Salmonella incidence post chill and post parts dip was low across all sample visits. CRISPR-SeroSeq analyses was performed on 55 samples that were collected over six visits to one plant and multiple serotypes were identified at each stage of processing. This study provides a potential alternative method for Salmonella culturing, which reduces the time required for Salmonella isolation. Further, the serotype population analyses by CRISPR-SeroSeq provides a new framework for monitoring Salmonella populations during processing. |
