Submitted to: Official Methods of Analysis of AOAC International
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/18/2010
Publication Date: 5/20/2011
Citation: Kamisaki-Horikoshi, M., Okada, Y., Takeshita, K., Sameshima, T., Kawasaki, S., Kawamoto, S., Fratamico, P.M. 2011. Evaluation of TA10 Broth for Recovery of Heat- and Freeze-Injured Salmonella from Beef. Official Methods of Analysis of AOAC International. 94:857-862. Interpretive Summary: Bacteria belonging to the genus Salmonella are important food-borne pathogens that cause an estimated 1.4 million cases of illness each year in the U.S. Food of animal origin and contaminated fruits and vegetables are important vehicles of infection. To prevent illnesses caused by Salmonella, the availability of reliable methods for detection of that pathogen in foods is critical. Furthermore, different interventions or processing conditions may result in injured Salmonella cells that are no longer detectable by enrichment but that are able to cause illness when consumed with the food. Therefore, in the current investigation, different enrichment media were evaluated to determine their ability to allow growth of different Salmonella serotypes that were subjected to freezing and heat stress for subsequent detection by culturing on selective broth and agar media. A broth developed in our laboratory, known as TA10, was superior to lactose broth, buffered peptone water, and universal preenrichment broth for recovery of freeze-injured or heat-injured Salmonella inoculated in ground beef at various concentrations. Therefore, TA10 broth should be used instead of commonly used liquid media for testing of beef that may be contaminated with heat- and freeze-injured Salmonella serotypes.
Technical Abstract: The Bacteriological Analytical Manual (BAM) Salmonella pre-enrichment broth (lactose [LAC] broth), buffered peptone water (BPW), and universal preenrichment (UP) broth were compared with TA10 broth, developed in our laboratory, for recovery of heat- and freeze-injured Salmonella (55ºC for 2-20 min and -20ºC for 2 months, respectively) from beef. Beef samples were contaminated with single Salmonella serovars, and contamination levels of 0.44 to <0.001 MPN / g and 0.74 to 0.14 MPN / g were used for heat-induced and freezing-induced injury studies, respectively. Twenty test portions (25 g) of the contaminated beef were pre-enriched in each broth, and the BAM Salmonella culture method was used thereafter. There was a significant difference in recovery of heat-injured Salmonella between TA10 broth and LAC broth (189 versus 156 positive samples, respectively) determined by plating onto selective agars and identification by biochemical tests. For the recovery of freeze-injured Salmonella, there was a significant difference between TA10 broth and LAC broth (189 versus 133 positive samples, respectively). TA10 broth was more effective than not only LAC broth but also UP broth for recovery of freeze-injured Salmonella. The results indicate that TA10 broth should be used instead of LAC broth for testing of beef that may be contaminated with heat- and freeze-injured Salmonella spp.