Use of enrichment real time-Polymerase Chain Reaction to enumerate Salmonella on chicken parts

Authors: Oscar, Thomas

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2014
Publication Date: 7/1/2014
Publication URL: https://handle.nal.usda.gov/10113/59554
Citation: Oscar, T.P. 2014. Use of enrichment real tme-Polymerase Chain Reaction to enumerate Salmonella on chicken parts. Journal of Food Protection. 77(7):1086-1092.

Interpretive Summary: Salmonella that survive cooking or that cross-contaminate other food during meal preparation represent primary routes of consumer exposure to this pathogen from chicken. Consequently, a study was undertaken to provide new information on incidence, number, and type of Salmonella on raw chicken parts at retail and on cooked chicken exposed to utensils used to process raw chicken during simulated meal preparation. Results of the survey indicated that 70% of the chickens were contaminated with Salmonella and that 19% of the cut-up parts were contaminated with Salmonella. Results of risk assessments for Salmonella in chicken show that lightly contaminated chicken at retail can pose a higher risk of illness than highly contaminated chicken if by random chance they are temperature abused, undercooked, and consumed by someone at high risk for infection. Therefore, it is important that consumers properly store, handle, and cook chicken to minimize the risk of illness from Salmonella, which is often present.

Technical Abstract: Salmonella that survive cooking and that cross-contaminate other food during meal preparation and serving represent primary routes of consumer exposure to this pathogen from chicken. Consequently, the present study was undertaken to use enrichment real time-polymerase chain reaction (RT-PCR) to enumerate Salmonella that contaminate raw chicken parts at retail and that cross-contaminate cooked chicken during simulated meal preparation and serving. Whole raw chickens obtained at retail were partitioned into wings, breasts, thighs, and drumsticks using a sterilized knife and cutting board. To study cross-contamination, the knife, board, and latex gloves used to partition the raw chicken were used to partition a cooked chicken breast. Chicken parts were incubated in 400 ml of buffered peptone water for 8 h at 40°C and 80 rpm. After enrichment, one ml samples were used for RT-PCR and cultural isolation of Salmonella. In some experiments, chicken parts were spiked with 0 to 3.6 log10 of Salmonella Typhimurium var 5- to generate standard curves for enumeration by RT-PCR. Of 10 raw chickens examined seven (70%) had one or more parts contaminated with Salmonella. Of 80 raw parts examined 15 (19%) were contaminated with Salmonella. Of 20 cooked chicken parts examined two (10%) were contaminated with Salmonella. Predominant serotypes identified were Typhimurium (71%) and its variants (var 5-, monophasic, and nonmotile) and Kentucky (18%). The number of Salmonella on contaminated parts ranged from one to two per part. Results of this study indicate that retail chicken parts examined were contaminated with low levels of Salmonella and resulted in low levels of cross-contamination during simulated meal preparation and serving. Thus, as long as consumers properly handle and prepare the chicken it should pose no or very low risk of consumer exposure to Salmonella.