Fate of Escherichia coli 0157 : H7, Salmonella Typhimurium DT 104, and Listeria monoctyogenes in fresh meat decontamination fluids at 4 and 10 degrees C

Bacterial pathogens may colonize meat plants and increase food safety risks following survival, stress hardening, or proliferation in meat decontamina tion fluids (washings). The objective of this study was to evaluate the abi lity of Escherichia coli O157:H7, Salmonella Typhimurium DT 104, and Lister ia monocytogenes to survive or grow in spray-washing fluids from fresh beef top rounds sprayed with water (10 or 85 degreesC) or acid solutions (2% la ctic or acetic acid, 55 degreesC) during storage of the washings at 4 or 10 degreesC in air to simulate plant conditions. Inoculated Sallmonella Typhi murium DT 104 (5.4 +/- 0.1 log CFU/ml) died off in lactate (pH 2.4 +/- 0.1) and acetate (pH 3.1 +/- 0.2) washings by 2 days at either storage temperat ure. In contrast, inoculated E. coli O157:H7 (5.2 +/-4 0.1 log CFU/ml) and L. monocytogenes (5.4 +/- 0.1 log CFU/ml) survived in lactate washings for at least 2 days and in acetate washings for at least 7 and 4 days, respecti vely: their survival was better in acidic washings stored at 4 degreesC tha n at 10 degreesC. All inoculated pathogens survived in nonacid (pH > 6.0) w ashings, but their fate was different. E. coli O157:H7 did not grow at eith er temperature in water washings, whereas Salmonella Typhimurium DT 104 fai led to multiply at 4 degreesC but increased by approximately 2 logs at 10 d egreesC. L. monocytogenes multiplied (0.6 to 1.3 logs) at both temperatures in water washings. These results indicated that bacterial pathogens may su rvive for several days in acidic, and proliferate in water, washings of mea t, serving as potential cross-contamination sources, if pathogen niches are established in the plant. The responses of surviving pathogens in meat dec ontamination waste fluids to acid or other stresses need to be addressed to better evaluate potential food safety risks.