Comparison of the metabolic responses of eight Escherichia coli strains including the “big six” in pea sprouts to low concentration electrolysed water by NMR spectroscopy

Abstract

The antimicrobial effects of low concentration electrolysed water (LcEW) on common foodborne pathogens have been well documented; however, the effects on six emerging Escherichia coli serotypes (the “big six”) remained unknown. Using pea sprouts as the food matrix, this in vivo study examined the sanitising efficacy of a 10-min LcEW treatment against eight E. coli strains (non-pathogenic E. coli ATCC 25922, pathogenic E. coli O26:H11, O45:H2, O103:H11, O111, O121:H19, O145 and O157:H7). The metabolic responses of the strains were further analysed using nuclear magnetic resonance (NMR) spectroscopy. An overall negative correlation between the resistance to LcEW and the magnitude of metabolic variation was observed. The metabolic status and pathways of the most resistant O103:H11 and O45:H2 strains were the least affected. The O26:H11 and O145 strains which demonstrated the highest sensitivity to LcEW had an array of metabolites depleted and had multiple pathways involved in amino acid metabolism, energy metabolism as well as osmotic and oxidative protection perturbed. Distinctive metabolic responses were detected in ATCC 25922, suggesting that alternative stress defence mechanisms may be present in the non-pathogenic E. coli strain. Amongst the pathogenic strains, the most unique metabolic responses were illustrated by O121:H19. Overall, the study showed that the NMR-based metabolomics is promising in elucidating the metabolic changes of various E. coli strains in pea sprouts during an antimicrobial process. It also provides clue for controlling “big six” contamination in fresh produce.