100A-29 |
Evaluation of overnight enrichment and next day detection of Salmonella in food matrices |
S. S. Rowe, E. P. Jeffries, C. C. YOUNG, and J. A. White. Research and Development, IGEN International, Inc., 16020 Industrial Dr., Gaithersburg, MD 20877 Rapid detection methods for the presumptive identification of Salmonella usually rely on enrichment times of at least 40 hours. However, the development of more sensitive methods will result in faster enrichment times. The PATHIGEN Salmonella Test is an extremely sensitive rapid detection method with a limit of detection of approximately 1000 cells. In this study, the ability of the PATHIGEN Salmonella Test to detect Salmonella in a variety of food matrices following enrichment times as short as 24 hours was investigated. Five food matrices including hot dogs, chicken, shrimp, cheese, and lettuce were tested. All food matrices were spiked with low (1-10 cfu/g) and high (10-50 cfu/g) numbers of Salmonella Typhimurium and enriched for 18 hours in Buffered Peptone Water to recover injured cells. A 100 uL volume of each enrichment was then transferred to 10 mLs of Rappaport-Vassiliadis Soya Peptone Broth (RVS) and incubated for 6 hours prior to detection using the PATHIGEN Salmonella Test. This method was compared against the BAM plating method in which identically prepared samples were enriched overnight in Lactose Broth followed by a second overnight enrichment in Tetrathionate Broth and RVS followed by plating. In this study, of the 100 samples tested at the low level spike, 81 were positive using the PATHIGEN Test while 80 were positive by the BAM method. For the high level spike, 95 were positive by the PATHIGEN Test and 95 were positive by the BAM method. Overall, the two detection methods were statistically equivalent but the PATHIGEN Salmonella test provided a result within 26 hours as opposed to 4 days for the plating method.
Session 100A, Food Microbiology: General II
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