Survival and Dissemination of Escherichia coli O157:H7 on Physically and Biologically Damaged Lettuce Plants

The ecology of the vegetable leaf surface is important to the survival of enteric pathogens. Understanding changes in ecological parameters during the preharvest stages of production can lead to development of approaches to minimize the hazard of contamination of fresh fruits and vegetables with foodborne pathogens. In this study, survival levels of Escherichia coli O157 over a 10-day period were compared among traumatically injured, phytopathogen-damaged, and healthy lettuce plants. Leaves from lettuce plants cracked along the central vein, plants infected with Xanthomonas campestris pv. vitians, and healthy plants were inoculated with E. coli O157:H7. The presence of E. coli O157:H7 populations on inoculated leaves and non-inoculated leaves of these same plants was determined for 10 days. The density of E. coli O157:H7 decreased over time on the inoculated leaves regardless of the treatment. The population of E. coli O157:H7 remained higher on traumatically injured leaves than on healthy plants (P < 0.001). E. coli O157:H7 was detected on leaves other than the direct inoculation site of the enteric pathogen in all three treatments groups. Preharvest damage, especially that caused by traumatic injury, impacted the survivability of E. coli O157:H7. Maintaining healthy plants and minimizing physical damage around the time of harvest might improve the safety of fresh produce.