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Methicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant microorganism and the principal nosocomial pathogen worldwide. The antibacterial activity of lactic acid bacteria against MRSA from ten human clinical isolates as well as MRSA standard strain ATCC 43300 was tested in vitro. The Lactobacillus (Lb.) strains (Lb. acidophilus CL1285(®) and Lb. casei LBC80R) as pure cultures, which came from commercial food products were employed. The growth inhibitory effect produced by the antimicrobial activity of the lactic acid bacteria on the MRSA strains was tested on solid medium using agar diffusion methods as well as a using a liquid medium procedure that contained a mixture of MRSA and lactic acid bacteria cultures. In the latter instance, we were able to demonstrate that the direct interaction of lactic acid bacteria and MRSA in such a mixture led to the elimination of 99% of the MRSA cells after 24 h of their incubation at 37°C.

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The present study was undertaken to evaluate the effect of ascorbic acid concentrations (0.03 to 0.5%) and irradiation doses (0.5 to 4 kGy) on microbial growth, color coordinates (L, a, and b), and sensory characteristics (taste and odor) of beef patties during storage at 4 +/- 1 degrees C. Ascorbic acid was also compared to citric acid at a similar pH value in order to differentiate the effects of ascorbic acid from those of pH reduction. Results showed significant reduction (p< or = 0.05) of aerobic plate counts (APCs) and total coliforms, and a significant interaction (p< or = 0.05) between ascorbic acid and irradiation dose was observed. The irradiation treatment had detrimental effects on redness, yellowness, and hue angle values of meat. However, incorporation of ascorbic acid into the meat before irradiation resulted in significant (p< or = 0.05) stabilization of color parameters. The color improvement obtained with ascorbic acid was not related to the pH reduction. Also, no significant detrimental effect on taste or odor was found in irradiated samples containing ascorbic acid.