Detection of Salmonella serotypes by overnight incubation of entire broiler carcass

Authors: Berrang, Mark; Cox Jr, Nelson; Cosby, Douglas; Frye, Jonathan; Jackson, Charlene

Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2016
Publication Date: 6/7/2016
Citation: Berrang, M.E., Cox Jr, N.A., Cosby, D.E., Frye, J.G., Jackson, C.R. 2016. Detection of Salmonella serotypes by overnight incubation of entire broiler carcass. Journal of Food Safety. doi: 10.1111/jfs.12298.

Interpretive Summary: Salmonella is a human bacterial pathogen that has been associated with poultry and poultry meat. There are several ways to sample a broiler carcass for detection of this organism. In the USA, a common method is a whole carcass rinse followed by incubation of a 30 mL portion of the rinse liquid (aliquot method). A more sensitive method is incubating the entire carcass overnight in 400 mL of rinse liquid (whole carcass enrichment). We compared these two methods with freshly processed broiler carcasses collected directly after all microbial interventions in a commercial slaughter plant. We found that Salmonella was detected much more often using the whole carcass enrichment method (59%) than with the aliquot method (15%). The aliquot method, however, performed better than expected detecting 26% of the positives that the enrichment method did, even though only 7.5% of the rinse was analyzed. Although, for the most part, the same serotypes of Salmonella were detected by both methods, many more of each type were found by whole carcass enrichment. Whole carcass enrichment is a useful research tool for determining the actual prevalence of Salmonella and can be used to determine the relative sensitivity of other methods such as the aliquot method. This information will be useful to researchers as they compare methods and test novel broiler carcass intervention strategies.

Technical Abstract: Salmonella is a human bacterial pathogen that has been associated with poultry and poultry products. There are multiple ways to sample broiler chicken carcasses for the prevalence of Salmonella. A common method in the USA is a whole carcass rinse and culture of an aliquot of the rinse. The objective of this study was to compare the sensitivity of the rinse aliquot method to overnight enrichment of the entire carcass in the rinse liquid. Fourteen replicate samplings were done, seven at each of two commercial broiler processing plants. Each replication included eight carcasses. Each carcass was subjected to a whole carcass rinse in buffered peptone from which 30 mL was removed and added to 30 mL fresh buffered peptone (rinse aliquot sample). The aliquot sample and the carcass, in the remaining buffered peptone, were incubated overnight prior to standard selective enrichment and plating for Salmonella detection. Salmonella was detected in 15% of rinse aliquot samples and 59% of whole carcass enrichment samples. Salmonella was found more frequently by whole carcass enrichment, however, when detected by both methods, for the most part, the same serotypes were found on individual carcasses. Whole carcass enrichment was shown to be more sensitive than rinse aliquot method, and likely detects Salmonellae even when tightly bound to the carcass or present in very low numbers. As such, whole carcass enrichment is a useful research tool to determine Salmonella prevalence.