Prophage induction reduces Shiga toxin producing Escherichia coli (STEC) and Salmonella enterica on tomatoes and spinach: A model study

Prophage induction reduces Shiga toxin producing Escherichia coli (STEC) and Salmonella enterica... Fresh produce is increasingly implicated in foodborne outbreaks and most fresh produce is consumed raw, emphasizing the need to develop non-thermal methods to control foodborne pathogens. This study investigates bacterial cell lysis through induction of prophages as a novel approach to control foodborne bacterial pathogens on fresh produce. Shiga toxin producing Escherichia coli (STEC) and Salmonella enterica isolates were exposed to different prophage inducers (i.e. mitomycin C or streptonigrin) and growth of the cells was monitored by measuring the optical density (OD600) during incubation at 37 °C. Beginning at three hours after addition of the inducer, all concentrations (0.5, 1, 2 μg/mL) of mitomycin C, or 2 μg/mL streptonigrin significantly reduced the OD600 in broth cultures, in a concentration dependent manner, relative to cultures where no inducer was added. PCR confirmed bacterial release of induced bacteriophages and demonstrated that a single compound could successfully induce multiple types of prophages. The ability of mitomycin C to induce prophages in STEC O157:H7 and in S. enterica (serovars Typhimurium and Newport) on fresh produce was evaluated by inoculating red greenhouse tomatoes or spinach leaves with 5 × 107 and 5 × 108 colony forming units, respectively. After allowing time for the inoculum to dry on the fresh produce samples, 6 μg/mL mitomycin C was sprayed onto each sample, while control samples were sprayed with water. Following overnight incubation at 4 °C, the bacterial cells were recovered and plate counts were performed. A 3 log reduction in STEC O157:H7 cells was observed on tomatoes sprayed with mitomycin C compared to those sprayed with water, while a 1 log reduction was obtained on spinach. Similarly, spraying mitomycin C on tomatoes and spinach inoculated with S. enterica isolates resulted in a 1-1.5 log and 2 log reduction, respectively. These findings serve as a proof of concept that prophage induction can effectively control bacterial foodborne pathogens on fresh produce. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Food Control Elsevier

Prophage induction reduces Shiga toxin producing Escherichia coli (STEC) and Salmonella enterica on tomatoes and spinach: A model study

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Publisher
Elsevier
Copyright
Copyright © 2018 Elsevier Ltd
ISSN
0956-7135
eISSN
1873-7129
D.O.I.
10.1016/j.foodcont.2018.02.001
Publisher site
See Article on Publisher Site

Abstract

Fresh produce is increasingly implicated in foodborne outbreaks and most fresh produce is consumed raw, emphasizing the need to develop non-thermal methods to control foodborne pathogens. This study investigates bacterial cell lysis through induction of prophages as a novel approach to control foodborne bacterial pathogens on fresh produce. Shiga toxin producing Escherichia coli (STEC) and Salmonella enterica isolates were exposed to different prophage inducers (i.e. mitomycin C or streptonigrin) and growth of the cells was monitored by measuring the optical density (OD600) during incubation at 37 °C. Beginning at three hours after addition of the inducer, all concentrations (0.5, 1, 2 μg/mL) of mitomycin C, or 2 μg/mL streptonigrin significantly reduced the OD600 in broth cultures, in a concentration dependent manner, relative to cultures where no inducer was added. PCR confirmed bacterial release of induced bacteriophages and demonstrated that a single compound could successfully induce multiple types of prophages. The ability of mitomycin C to induce prophages in STEC O157:H7 and in S. enterica (serovars Typhimurium and Newport) on fresh produce was evaluated by inoculating red greenhouse tomatoes or spinach leaves with 5 × 107 and 5 × 108 colony forming units, respectively. After allowing time for the inoculum to dry on the fresh produce samples, 6 μg/mL mitomycin C was sprayed onto each sample, while control samples were sprayed with water. Following overnight incubation at 4 °C, the bacterial cells were recovered and plate counts were performed. A 3 log reduction in STEC O157:H7 cells was observed on tomatoes sprayed with mitomycin C compared to those sprayed with water, while a 1 log reduction was obtained on spinach. Similarly, spraying mitomycin C on tomatoes and spinach inoculated with S. enterica isolates resulted in a 1-1.5 log and 2 log reduction, respectively. These findings serve as a proof of concept that prophage induction can effectively control bacterial foodborne pathogens on fresh produce.

Journal

Food ControlElsevier

Published: Jul 1, 2018

References

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