Pathogen physiological state has a greater effect on outcomes of challenge and validation studies than strain diversity

Assembly of a collection of Salmonella, L. monocytogenes, shiga toxin-producing E. coli, and rele-vant surrogate, indicator, and index organisms representing national and international strain diversity associated with produce. Evaluate the strains for (i) growth on different produce types and (ii) survival of key produce relevant controls and intervention treatments (e.g., different sanitizers). Expose selected pathogen strains (at least 5 per target pathogen) to different environmental and stress conditions (e.g., different growth phases and water activities; pH stress) and evaluate them for subsequent (i) growth on different produce and fruit products and (ii) survival of key produce relevant controls and intervention treatments.