Evaluation of Wheat-Derived Bacteria as Surrogates for Validating Antimicrobial Inactivation of Foodborne Pathogens during Wheat Tempering
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EmailThis study isolated bacteria from various types of wheat grain and evaluated their potential to be used as surrogate for Salmonella and Shiga-toxin producing Escherichia coli (STEC) on low-moisture foods (LMFs).
Abstract
Selection of appropriate nonpathogenic surrogates is critical for validating intervention strategies targeting foodborne pathogens during processing. This study isolated bacteria from various types of wheat grain and evaluated their potential to be used as surrogate for Salmonella and Shiga-toxin producing Escherichia coli (STEC) on low-moisture foods (LMFs). Four Gram-negative isolates were selected (Pseudomonas alabamensis, Kosakonia cowanii, and two Pantoea agglomerans) and characterized for their growth, inoculum reproducibility, tolerance to 0.5% lactic acid; survival on grain after 4-week storage, and response to tempering using 5% lactic acid and 800 ppm chlorinated water when inoculated on wheat grain. Enterococcus faecium NRRL B-2354, a common surrogate for thermal validation in LMFs, was also evaluated. E. faecium NRRL B-2354 showed enhanced survival during storage and direct lactic acid exposure (P < 0.05). However, E. faecium responses to tempering treatments were comparable to those of the pathogens, indicating its suitability as surrogate for tempering. Further evaluation of E. faecium NRRL B-2354 for applications involving shelf-life studies or lactic acid treatments will be required. All wheat-derived isolates showed similar (P > 0.05) growth parameters, lactic acid tolerance, storage survival, and exhibited reductions not significantly different (P > 0.05) from those of the pathogens during tempering, indicating similar responses under low-moisture processing conditions. Genomic screening indicated limited antimicrobial resistance determinants and no virulence profiles suggestive of pathogenic potential among them. Overall, the results indicate that the wheat-derived isolates evaluated in this study are suitable surrogate candidates for assessing tempering interventions in wheat and could be used as surrogates for evaluating pathogen stability under wheat and flour storage environments.
