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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL MODELING AND BIOINFORMATICS FOR FOOD SAFETY AND SECURITY Title: An enumeration method and sampling plan for mapping the number and distribution of a multiple antibiotic resistant strain (ATCC 700408) of Salmonella typhimurium DT104 on the carcass of Cornish game hens

Author
item Oscar, Thomas

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 23, 2008
Publication Date: N/A

Interpretive Summary: The most common method used to determine the number of Salmonella on the chicken carcass is to rinse the whole carcass for one-minute and then count the number of Salmonella in the rinse fluid. However, only a small percentage of the bacteria, including Salmonella, are recovered in a one-minute rinse of the chicken carcass. In the current study, whole carcass parts from young chickens in the Cornish game hen class were incubated for 24 h in rinse fluid and a standard curve for determining the number of Salmonella on the chicken parts was developed. The new method will be used in future studies to more precisely determine the number and distribution of Salmonella contamination on the whole chicken carcass. This map of Salmonella contamination will then allow poultry companies to better target application of sanitizing chemicals to more effectively reduce or eliminate Salmonella contamination and the public health risk of Salmonella infection from freshly processed chickens.

Technical Abstract: Mapping the number and distribution of Salmonella on the chicken carcass will help guide better design of processing procedures to reduce or eliminate this human pathogen from chicken. A selective plating media with multiple antibiotics (XLH-CATS) and a multiple antibiotic resistant strain (ATCC 700408) of Salmonella Typhimurium definitive phage type 104 (DT104) were used to develop an enumeration method for mapping the number and distribution of S. Typhimurium DT104 on the carcasses of young chickens in the Cornish game hen class. The enumeration method was based on the concept that the time to detection by drop plating on XLH-CATS during incubation of whole chicken parts in buffered peptone water (BPW) would be inversely related to the initial log10 number (No) of S. Typhimurium DT104 on the chicken part. The sampling plan for mapping involved dividing the chicken into 12 parts that ranged in average size from 36 to 80-g. To develop the enumeration method, whole parts were spot inoculated with 0 to 6 log10 S. Typhimurium DT104 followed by incubation in 300 ml of BPW and detection on XLH-CATS by drop plating. An inverse relationship between detection time (DT, h) on XLH-CATS and No was found (r = -0.984). The standard curve was similar for the individual chicken parts and therefore, a single standard curve for all 12 chicken parts was developed. The final standard curve, which contained a 95% prediction interval for providing stochastic results for No, had high goodness-of-fit (r2 = 0.968) and was: No (log10) = 7.78 +/- 0.61 – (0.995*DT). Ninety-five percent of No were within +/- 0.61 log10 of the standard curve. The enumeration method and sampling plan will be used in future studies to map changes in the number and distribution of Salmonella on carcasses of young chickens fed the DT104 strain used in standard curve development.

Last Modified: 12/19/2014
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