Choice of an enrichment procedure introduces bias due to different parameters such as media used, method of sampling, number of colonies selected, length and temperature of incubation, etc. The most common method of sampling a broiler carcass (a one-minute rinse procedure) is insufficient to release all Salmonella present, particularly those that are firmly attached.
The inability to assess serovar diversity means serovars most often associated with human illness may be masked by Salmonella that are more abundant but pose a smaller public health risk.
Testing a new approach
The objective of this study was to compare presently used conventional methodology to a new technology (CRISPR-1seroSeq) to determine the presence of multiple Salmonella serotypes present on a prechilled broiler carcass. CRISPR-SeroSeq involves serotyping by sequencing clustered, regularly interspaced short palindromic repeats. This is an amplicon-based next-generation sequencing tool which allows the detection of multiple serovars and maps the relative frequencies in a sample.
The comparison was done by sampling eight chicken carcasses collected prechill in a commercial processing facility over two days. All eight carcasses were positive for Salmonella and all contained multiple serovars; with one carcass harboring nine serovars.
The study used a new sampling technology to find previously undetected Salmonella serotypes. This research brings potential implications for human health.
Many more serotypes were detected using CRISPR compared to conventional Salmonella isolation, and this new technology further demonstrated that across these carcasses multiple strains of some serovars were present.
This study was not done to show that there is more Salmonella on commercial poultry than was previously thought. For the Salmonella mitigation strategies such as vaccines to work effectively, one needs to know which serotypes predominate in a particular company, complex or farm and this technology can lead to the improvement of present-day vaccines.
Importantly, the sensitivity of CRISPR-SeroSeq can allow us to track masked or hidden serovars over time and, if they begin to increase, this information can provide our industry the ability to develop proactive serovar-specific controls in a timely manner.
Study: No link between line speed, Salmonella contamination: