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Issue
As part of its ongoing process of evaluating procedures to shorten the time it takes to obtain test results while maintaining analytical quality, the Food Safety and Inspection Service has adopted the BAX® system to screen ready-to-eat products for Listeria monocytogenes.
Background
FSIS conducts microbiological testing as a part of its pathogen reduction program for meat, poultry, and egg products. Thousands of samples are collected by inspectors each week and analyzed at the three FSIS field service laboratories.
FSIS uses screening tests to reduce the resources needed to analyze samples. A screening test indicates if a sample is potentially positive for a pathogen. If a sample tests negative for a pathogen screening test, no further analysis is done. If the screening test indicates a potential positive, further testing is done to confirm the screen results. FSIS previously used a screen test based on a color change. With that test, chemicals in a test tube are metabolized by the pathogen, causing a color change when Listeria monocytogenes is present.
BAX® System
The BAX® screening test uses a polymerase chain reaction to amplify DNA. If a pathogen is present in a sample, the BAX® system copies the DNA of the pathogen, producing enough DNA to be detected. If amplification occurs, the sample is analyzed further. If no amplification occurs, no further testing is done on the sample.
Evaluation Process
When a promising new testing method becomes available, the FSIS Microbial Outbreaks and Special Projects laboratory, in Athens, GA evaluates the new test to determine whether it would be beneficial to the agency. The laboratory evaluated the BAX® system for several months using unofficial samples.
The BAX® system was further evaluated at FSIS’s Eastern Field Service Laboratory in Athens, GA. Approximately 830 random official samples were screened for Listeria monocytogenes using the previous color change screening method and the BAX® system. The identification and confirmation methods did not change.
When the evaluation was completed, data were reviewed to determine if the BAX® system produced results comparable to those obtained using the color change method. Following successful evaluations, a decision was made in April 2002 to adopt the BAX® system to screen meat and poultry samples for Listeria monocytogenes.
Future Evaluations
FSIS plans to evaluate the BAX® system for Salmonella and E. coli O157:H7 for use in all three field service laboratories.
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