PhD, Vice President R&D, Jennie-O Turkey Store, Willmar, MN, U.S.A.
Salmonella is one of the more common causes of foodborne illness associated with meat and poultry products (1). The Pathogen Reduction and Hazard Analysis and Critical Control Point final rule established specific performance standards for Salmonella in raw meat and poultry products. As part of this rule, FSIS collects raw meat and poultry product samples from establishments and tests these samples for the presence of Salmonella. The stated objective of Salmonella measurement for the meat industry has been to reduce the level of pathogens in meat products. Measurement is the key to improving any process. In order for measurement to be most effective in improvement, there should be a cause and effect relationship between the measurement and the improvement. In other words, what you measure should be a primary cause of the result. The closer the measurement is to the primary cause, the more effective the measurement. This research was conducted in an attempt to establish a measurement on the live side of turkey production that would correlate with Salmonella levels in raw ground turkey at the processing plant. Barn litter was selected as a variable that would influence the presence of Salmonella in or on the bird in the preharvest area. Ground necks were selected as a material that would reflect the presence of Salmonella at the processing plant. In selecting measurement techniques, a quantitative measure of the level of Salmonella would be beneficial in determining a correlation of these variables. The technique of Real Time PCR was used to determine a semiquantitative count of Salmonella in litter and neck samples (2). Dr. Roy Radcliffe at Marshfield labs was instrumental in establishing these measurements (3). A test protocol was established to evaluate the use of Real Time PCR as a tool to identify farm conditions that would cause increased levels of Salmonella in raw ground turkey. Two different farm management groups were selected. Twenty farms from management group X and twenty farms from management group Y were identified. A flock from each farm and litter samples from the flock were to be analyzed during this test. The turkeys on farms from management group X were fed from a single feed mill. Farms from management group Y were also fed from a single, but different feed mill. Within 4 days of load out, 3 surface litter samples were collected at both ends and the middle of the barn. These samples were collected along a line near the centre of the barn. The litter samples were analyzed at Marshfield Labs utilizing Real Time PCR. At the processing plant, 10 ground neck samples were collected at the grinder from each flock. The testing was conducted over several months. To date, the results of these analysis show that the necks have a very low count of Salmonella. When Salmonella is detected in the necks, the count is usually at or near the level of detection (0.1 cfu/gm). The litter samples have a wide range of count, from zero up to 105 . The following chart shows a plot of neck incidence rate compared to the log of the litter count. (Correlation 0.70, p=.01). The results of the testing indicate a correlation between the count of Salmonella in the litter and the incidence rate of Salmonella in the ground necks.
When we compare the incidence rate in the litter and the necks by management group, we see a significant difference in the litter incidence rate and the neck incidence rate by management group.
A comparison of the count in the litter by management group shows group Y has significantly higher litter counts than the X group.
A similar distribution is seen with neck counts for Salmonella. In summary, these data indicate that Real Time PCR may be useful measurement in assessing Salmonella levels on the farm. Higher Salmonella levels on the farm at the time of harvest appear to influence Salmonella incidence in raw ground turkey neck.
- Tauxe, R., 1991 Salmonella: a post modern pathogen. J. Bood Prot. 54(7):563-568.
- S. A. Bustin, “Absolute quantification of mRNA using real-time reverse transcription polymerase chain reaction assays” Journal of Molecular Endocrinology, 2000, Vol. 25, pages 169-193.
- Dr. Roy. P. Radcliff, Marshfield Clinic Laboratories – Food Safety Services 1000 N. Oak Ave. Marshfield, WI 5449