Effect of phenolic compounds and cold shock on survival and virulence of Escherichia coli pathotypes

Phenolic compounds (PC) affect many metabolic processes of microbes; however, there is no information about their effectiveness when these act in combination with low temperatures for the control of Escherichia coli pathotypes. In this study, four PC, (tannic acid [TA], gallic acid [GA], methyl gallate [MG], and epigallocatechin gallate [EG]) in combination with cold shock (CS, 10°C) were evaluated for their effect on growth, swarming motility, biofilm formation, and expression of selected virulence‐related genes of E. coli pathotypes [enteropathogenic (EPEC), enterohemorrhagic (EHEC), and enterotoxigenic (ETEC)]. Subinhibitory concentrations of the PC were used alone (37°C) or in combination with CS. For CS assays, E. coli strains were grown at 37°C until mid‐log phase and then subjected to 10°C for 4 hr. Membrane damage was determined by flow cytometry; swarming motility was measured on soft‐LB agar, biofilm formation was analyzed by crystal violet staining, and gene expression of CS, biofilm, and swarming motility related‐genes was determined by qPCR. Subinhibitory concentrations of the PC did not affect the viability of the strains. The combination of CS + TA provoked the highest (p ≤ .05) mortality in all pathotypes. CS + GA inhibited (100%) the motility of EHEC and ETEC. PC and CS + PC reduced (p ≤ .05) biofilm formation. The combination of PC and CS affected virulence factors and their gene expression of pathogenic E. coli presenting a novel alternative for its control in foods. This article demonstrated that when combined, low temperatures with natural antimicrobials inhibited the growth of three Escherichia coli pathotypes (EPEC, EHEC, and ETEC) and enabled the reduction/inhibition of critical virulence‐related processes, such as swarming motility and biofilm, as well as alteration of the expression of cold shock proteins.