Synergistic effects of elevated hydrostatic pressure, mild heat, malic acid, and citricidal TM against wild-type, rifampicin-resistant, and pressure-stressed Shiga toxin-producing Escherichia coli

The application of high-pressure processing is gaining importance and momentum in the food industry. In this hurdle validation study, strain mixtures of Escherichia coli O157:H7 (STEC) and non-O157 serogroups (nSTEC) were used in three phenotypes of wild-type, rifampicin-resistant, and pressure-stressed. After a 48-hour habituation, elevated hydrostatic pressure of 300–600 MPa was tested. While 300 MPa treatments at 4.4°C resulted in 0.45 log reduction (P < 0.05) of STEC after 5 min, the same treatment resulted in 4.26 and 6.02 log reductions (P < 0.05) with the addition of malic acid and citricidalTM, respectively. Results of our study illustrate that application of selected antimicrobials could, to a great extent, augment the decontamination efficacy of pressure-based treatments. Additionally, we observed that the STEC and nSTEC serogroups of the pathogen have comparable sensitivity to elevated hydrostatic pressure and the antimicrobials. Thus, a validated treatment plan against STEC serogroups is most probably equally effective against nSTEC serogroups as well.