Reduction of multidrug-resistant and drug-susceptible Salmonella in ground beef and freshly harvested beef briskets after exposure to commonly used industry antimicrobial interventions.

Two separate studies were conducted to examine the differences in survivability of multidrug-resistant (MDR) and drug-susceptible Salmonella in fresh meats in a simulated industry environment. Beef trim from a commercial facility was inoculated with either MDR (AmpC phenotype) or drug-susceptible Salmonella (SUS) cocktails (10(6) CFU/ml). Antimicrobial interventions included 3% lactic acid (LA), 1,000 ppm of acidified sodium chloride (ASC), ambient water (AW), and an inoculated control with no intervention (CTRL). Each aliquot was ground and formed into patties and packaged using high-O(2) modified atmosphere packaging. Samples for microbiological evaluation were collected on days 0, 7, 10, and 14. In the second study, beef briskets were collected immediately after harvest. Inoculation and antimicrobial application were the same, except treatments were heated and there was an additional hot water treatment. All beef briskets were refrigerated, and samples were collected at 0, 6, and 24 h. For the first study, the overall effectiveness of the treatments (from most effective to least effective) was LA, ASC, CTRL, and AW. Significant differences were observed only between MDR and SUS Salmonella when AW was applied (P = 0.02), and bacterial loads with AW were significantly greater (P < 0.01) for MDR Salmonella. In the second study, the intervention effectiveness ranked LA, ASC, hot water, AW, and CTRL. Significant differences between MDR and SUS Salmonella levels were not detected for any intervention or sampling time point. These data indicate that MDR and SUS variants of Salmonella behave similarly in response to the antagonistic action of antimicrobials commonly used in beef facilities.