Impact of Pre-Harvest Environmental Factors on the Survival of Enterohemorrhagic E. Coli and Salmonella on Lettuce

Abstract

Enteric diseases linked to fresh produce consumption are on a rise. Pathogens can contaminate produce in the pre-harvest field and can survive for long time periods. Thus, this study quantified the survival of Enterohemorrhagic E.coli and Salmonella on pre-harvest lettuce under two relative humidity and seasonal conditions. The effect of relative humidity on pathogen survival depended on the seasonal conditions. The impact of chlorine stress on survival of the two pathogens after exposure to pre-harvest variables was also determined. A single EHEC strain developed resistance to chlorine after 3 days on lettuce plants. Gene expression analysis revealed the up-regulation of genes involved in osmotic and cell envelope stress. Up-regulation of a gene involved in oxidative stress was also observed which could possibly be responsible for imparting resistance to chlorine stress. Understanding these aspects will help develop effective post-harvest decontamination strategies to reduce consumer exposure to such pathogens on produce.