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Susceptibility of Escherichia coli O157 to chitosan-arginine in beef liquid purge is affected by bacterial cell growth phase



Here, we evaluated the impact of bacterial growth stage on the effect of chitosan-arginine (Ch-arg) on Escherichia coli O157:H7 cell numbers and metabolic activity within contaminated beef juice held at room temperature. Using a lux-marked metabolic reporter strain of E. coli O157:H7, the results showed that Ch-arg was most bioactive against cells in the lag phase and exponential phase. In comparison, there was a reduced, although still significant, inhibitory effect of Ch-arg on the viability and metabolic activity of E. coli O157 held in stationary phase. Ch-arg reduced, but did not eliminate E. coli O157 growth in the meat juice over 48 h. Based on the evidence presented here and elsewhere, we conclude that Ch-arg can limit the growth and activity of food spoilage bacteria; however, it cannot completely eliminate bacterial contaminants originally present. Ch-arg should therefore be viewed as a potentially protective measure rather than a biocidal agent that completely eliminates the risk of pathogen transfer in the food chain.