The rate of horizontal transmission of antibiotic resistance plasmids is increased in food preservation-stressed bacteria

Aim: The aim of this study was to investigate the possibility that sublethal food preservation stresses (high/low temperature, osmotic and pH stress) can alter the rate of horizontal transmission of antibiotic resistance (ABR) plasmids between Escherichia coli strains and between E. coli and Salmonella serotype Typhimurium. Methods and Results: Escherichia coli donor cultures, carrying F1 plasmid R386 and Inc I1 plasmid TP307 and E. coli and Salm. Typhimurium recipient cultures were prestressed under a range of sublethal environmental conditions (high/low temperature, osmotic and pH stress). The prestressed donor and recipient cultures were then mated and the transmission rate calculated. The study found that the horizontal transmission rate of plasmids R386 and TP307 was significantly increased (P < 0.05) when prestressed donor and recipient cells are mated under conditions of environmental stress. Conclusion: The results from this study indicate that, the sublethal stresses that food pathogens encounter in modern food preservation systems increase the inter- and intra-specific horizontal transmission of selected ABR plasmids. Significance and Impact of the Study: Increased use of bacteriostatic (sublethal), rather than bacteriocidal (lethal) food preservation systems, may be contributing to the dissemination of ABR among important food borne pathogens.