Effect of environmental stresses on antibody-based detection of Escherichia coli O157:H7, Salmonella enterica serotype Enteritidis and Listeria monocytogenes


Arun K. Bhunia, Department of Food Science, Molecular Food Microbiology Laboratory, 745 Agriculture Mall Dr., Purdue University, West Lafayette, IN, 47907-2009, USA.
E-mail: bhunia@purdue.edu


Aims:  To study the reaction patterns of selected antibodies to Escherichia coli O157:H7, Salmonella enterica serotype Enteritidis and Listeria monocytogenes cells exposed to various environmental stresses.

Methods and Results: Escherichia coli O157:H7, Salmonella Enteritidis and L. monocytogenes cells subjected to different environmental stress of temperatures (4 and 45°C), NaCl (5·5%), oxidative stress (15 mmol−1 H2O2), acidic pH (5·5) and ethanol (5%) for 3 h (short-term stress) or for 5 days (long-term stress) were analysed by ELISA and Western blotting. The ELISA results indicated that most stresses caused 12–16% reductions in reaction for anti-E. coli O157:H7 and 20–48% reductions for anti-Salmonella polyclonal antibodies during short-term stress, whereas the most stresses exhibited enhanced reaction (44–100% increase) with the anti-L. monocytogenes polyclonal antibody. During long-term stress exposure to combined stress conditions of pH 5·5, 3·5% NaCl at 12°C or at 4°C, antibody reactions to the three pathogens were highly variable with the combined stress at 4°C showing the most reductions (8–40%). Likewise, there were about 18–59% reductions in antibody reactions with pathogens when cultured in hotdog samples with the combined stress conditions. Western blot analyses of crude cell surface antigens from both short- and long-term stressed cells revealed that the changes in antibody reactions observed in ELISA were either because of repression, expression or possible denaturation of antigens on the surface of cells.

Conclusions:  Overall, the antibody reactions were significantly reduced in pathogens exposed to both short- and long-term environmental stresses in culture medium or in meat sample because of expression, repression or denaturation of specific antigens in cells.

Significance and Impact of the Study:  In order to ensure the reliable detection of foodborne pathogens using antibody-based methods, the influence of stress on antibody reactions should be thoroughly examined and understood first as the physiological activities in cells are often altered in response to a stress.