Purpose: It has become common industry practice to test large composite samples of food for pathogens, especially with a 375g size. The iQ-Check kit is a real-time PCR method utilizing a novel fluorescent double stranded DNA hybridization probe for detection of Salmonella. A modification of the current AOAC Performance Tested Method (#010803) has been completed using a 375g sample size.
Methods: In an independent method comparison study, the test method was compared to the USDA FSIS Microbiology Laboratory Guidebook reference method for the analysis of raw ground chicken and deli ham and to the US FDA Bacteriological Analytical Manual reference method for the analysis of dry dog food and non-fat dry milk powder. Thirty samples were tested for each matrix, 5 uninoculated, 20 low level fractional positive and 5 high level. A food-to-media dilution ratio of 1:4 was tested to decrease the volume of liquid broth needed with this large sample size. The iQ-Check Prep automation system was utilized for DNA extraction and PCR preparation.
Results: The proportion of positive analytical outcomes for each matrix at a given level was calculated by using POD statistics. Results demonstrated there was no significant difference in the performance of the test method when compared to the appropriate reference method.
Significance: The method presented provides users a validated method for detection of Salmonella from a large 375g sample size with the proven accuracy of real-time PCR. The use of the automation system allowed users to tend to other lab duties while the instrument processed the samples. It also provided sample traceability.