Effect of heat‐assisted pulsed electric fields and bacteriophage on enterohemorrhagic Escherichia coli O157:H7

Pulsed electric fields (PEF), heat‐assisted PEF (H‐PEF), and virulent bacteriophage (VP) are non‐thermal techniques for pathogen inactivation in liquids that were investigated individually, and in combination (PEF/VP, H‐PEF/VP) to control enterohemorrhagic Escherichia coli (EHEC) O157:H7 in Luria‐Bertani broth (LBB) and Ringer's solution (RS). Treated cells were subsequently incubated at refrigeration (4°C) and temperature‐abuse conditions (12°C) for 5 days. When EHEC cells grown in LBB were subjected to non‐thermal processing and subsequently stored at 12°C for 5 days, reductions in count of between 0.1 and 0.6 log cycles were observed and following storage at 4°C the decrease in counts varied between 0.2 and 1.1 log₁₀. For bacteria cells suspended in RS values ranged from 0.1 to ≥3.9 log cycles at both storage temperatures. The most effective treatments were H‐PEF and H‐PEF/VP, both producing a >3.4 log cycle reduction of cells suspended in non‐nutrient RS. Analysis of EHEC recovery on selective and non‐selective media indicated no occurrence of sub‐lethal damage for VP, PEF/VP, and H‐PEF/VP‐treated cells. The findings indicate that combining PEF and lytic phage may represent a suitable alternative to conventional fluid decontamination following further process optimization. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 31:110–118, 2015