|Cason jr, John|
Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/5/2003
Publication Date: 10/1/2003
Citation: Simmons, M., Fletcher, D.L., Berrang, M.E., Cason Jr, J.A. 2003. Comparison of sampling methodology for the detection of salmonella on whole broiler carcasses purchased from retail outlets. Journal of Food Protection. 66(10):1768-1770. Interpretive Summary: In an earlier study we showed that, when a very sensitive method was employed, salmonellae could be recovered from 34 % of broiler carcasses purchased at retail outlets. Regulatory samples are collected in the processing plant with a less exhaustive recovery method. The less exhaustive method is done before packaging, distribution and retail display and has resulted in data showing 10.4 % of broiler carcasses are positive for salmonellae. The current study was done to determine if the apparent difference in salmonellae prevalence could be explained by recovery methodology. Broiler carcasses were purchased at grocery stores. Each carcass was subjected to a rinse, an aliquot of the rinse was cultured for salmonellae. The same carcass was then incubated overnight in a bacterial recovery broth which was then cultured for salmonellae. Salmonellae recovery from the aliquot of the rinse and the whole carcass enrichment were compared. The aliquot method resulted in 13% positive while the whole carcass enrichment method yielded 38% positive. These results show that when comparing two sets of salmonellae prevalence data it is of utmost importance to use the same recovery method.
Technical Abstract: An experiment was conducted to compare two Salmonella recovery methods from the same carcass. One hundred fresh, whole broiler chickens were purchased from retail outlets over a 5-week period (20 carcasses per week). After carcasses were aseptically removed from the packages and giblets removed, the carcasses were placed in sterile bags containing 400 ml of 1% buffered peptone, shaken for 60 s, and then a 30 ml aliquot was removed and incubated for 24h at 37 C (aliquot sample). Immediately, an additional 130ml of 1% buffered peptone was added to the bag with the same carcass, bringing the volume to 500 ml, after which the carcass was re-shaken and the whole carcass and rinse were incubated for 24h at 37C (whole carcass enrichment sample). Following incubation, a 0.5 ml sample from each method was placed into 10 ml each of Rappaport-Vassiliadis and tetrathionate (Hajna) broth and incubated at 42 C for 24 h. Each broth was then streaked onto BG Sulfa agar and modified lysine iron agar, and incubated for 24 h at 35 C. Suspect Salmonella colonies were inoculated on triple sugar iron and lysine iron agar slants and incubated at 35 C for 24 h. Presumptive positives were confirmed using Poly O and Poly H agglutination tests. Over the five week period, the Aliquot sample had 13 % Salmonella-positive carcasses compared to 38 % for the whole carcass enrichment (WCE) sample, from the same carcasses. Recovery ranged from 0/20 to 4/20 for Aliquot method, and 4/20 to 10/20 for WCE method over the 5 week period. These results indicate that when low numbers of Salmonella are expected, sampling methodology has a major influence on the identification of Salmonella-positive carcasses.