Assembly and Characterization of a Pathogen Strain Collection for Produce Safety Applications: Pre-growth Conditions Have a Larger Effect on Peroxyacetic Acid Tolerance Than Strain Diversity

Effective control of foodborne pathogens on produce requires science-based validation of interventions and control strategies, which typically involves challenge studies with a set of bacterial strains representing the target pathogens or appropriate surrogates. In order to facilitate these types of studies, a produce-relevant strain collection was assembled to represent strains from produce outbreaks or pre-harvest environments, including L. monocytogenes (n=11), S. enterica (n=23), shiga-toxin producing E. coli (STEC) (n=13), and possible surrogate organisms (n=8); all strains were characterized by whole genome sequencing (WGS). Strain diversity was assured by including the 10 most common S. enterica serotypes, L. monocytogenes lineages I-IV, and E. coli O157 as well as selected “non-O157” STEC serotypes. As it has previously been shown that strains and genetic lineages of a pathogen may differ in their ability to survive different stress conditions, a subset of representative strains for each “pathogen group” (e.g., Salmonella, STEC) was selected and assessed for survival of exposure to peroxyacetic acid (PAA) using strains pre-grown under different conditions including (i) low pH, (ii) high salt, (iii) reduced water activity, (iv) different growth phases, (v) minimal medium, and (vi) different temperatures (21°C, 37°C). The results showed that across the three pathogen groups pre-growth conditions had a larger effect on bacterial reduction after PAA exposure as ...
Source: Frontiers in Microbiology - Category: Microbiology Source Type: research