Potential resistance to antimicrobials shown by certain bacteria.An increased prevalence of bacteria resistant to therapeutic antibiotics has led to a greater risk for illnesses that are difficult to treat using currently available antibiotics. The emergence of such antibiotic-resistant organisms should be of concern to food processors who should use more and varied antimicrobial preservation techniques to control foodborne pathogens. However, there are little or no data on the possible emergence of foodborne pathogens resistant to traditional food antimicrobials, such as organic acids. A few scientists believe that some foodborne pathogens can be resistant to traditional food antimicrobials. And research bears this out. For example, there is a potential for the development of resistance by L. monocytogenes or S. typhimurium to regulatory-approved food antimicrobials at certain concentrations and pH. Scientists at the University of Tennessee The University of Tennessee (UT), sometimes called the University of Tennessee at Knoxville (UT Knoxville or UTK), is the flagship institution of the statewide land-grant University of Tennessee public university system in the American state of Tennessee. investigated the potential development of resistance to certain antimicrobials. They evaluated the potential mechanisms of microbial microbial pertaining to or emanating from a microbe. microbial digestion the breakdown of organic material, especially feedstuffs, by microbial organisms. resistance associated with specific microorganisms. Four strains of L. monocytogenes (101, 108, 310 and Scott A) and S. typhimurium DT 104 (2380, 2576, 2582 and 2486) were used in this research. Food antimicrobials evaluated included sodium benzoate sodium benzoate or benzoate of soda, chemical compound, C6H5CO2Na, colorless or white crystalline, aromatic compound; the sodium salt of benzoic acid. , potassium sorbate Potassium sorbate is a mild preservative. Its primary use is as a food preservative (E number 202). Its molecular formula is C6H7O2K and its systematic name is potassium (E,E)-hexa-2,4-dienoate. and sodium lactate Lactate A salt or ester of lactic acid (CH3CHOHCOOH). In lactates, the acidic hydrogen of the carboxyl group has been replaced by a metal or an organic radical. Lactates are optically active, with a chiral center at carbon 2. . Researchers monitored growth using a micro-broth dilution assay and measuring absorbance absorbance /ab·sor·bance/ (-sor´bans) 1. in analytical chemistry, a measure of the light that a solution does not transmit compared to a pure solution. Symbol . 2. at 630 nm. Bacterial strains were exposed to increasing concentrations of each antimicrobial up to 0.5% at pH 6.0 without any pre-stress. L. monocytogenes showed growth in the presence of increasing concentrations--0.1% to 0.5%--of all the antimicrobial compounds tested, with the exception of 0.5% sodium benzoate. Sodium lactate had little effect on the growth of any strain, except L. monocytogenes 101 at 0.4% to 0.5% levels. S. typhimurium growth was inhibited using more than 0.3% benzoic and more than 0.4% sorbic acid sorbic acid /sor·bic ac·id/ (sor´bik) a fungistat used as an antimicrobial inhibitor in pharmaceuticals. sor·bic acid n. . As with L. monocytogenes, sodium lactate had little effect on the growth of any strain of S. typhimurium. Both microorganisms showed potential for resistance to sodium lactate and to lower concentrations of benzoate benzoate /ben·zo·ate/ (ben´zo-at) a salt of benzoic acid. ben·zo·ate n. A salt or ester of benzoic acid. benzoate a salt of benzoic acid. and sorbate. Further information. P. Michael Davidson, Department of Food Science and Technology, University of Tennessee, 101 Food Safety and Processing, 2605 River Dr., Knoxville, TN 37996; phone: 865-974-0098; fax: 865-974-2750; email: pmdavidson@utk.edu. |
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