Lytic Escherichia phage OSYSP acts additively and synergistically with gaseous ozone against Escherichia coli O157:H7 on spinach leaves

• Published in: Scientific reports Vol. 13; no. 1; p. 10706
• Main Authors: Yesil, Mustafa, Kasler, David R, Huang, En, Yousef, Ahmed E
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 03.07.2023; Nature Publishing Group UK; Nature Portfolio
• Subjects: Bacteriophages; Colony Count, Microbial; Cooling; E coli; Enumeration; Escherichia; Escherichia coli; Escherichia coli O157; Food Microbiology; Foodborne pathogens; Inoculum; Ozonation; Ozone; Ozone - pharmacology; Pathogens; Phages; Plant Leaves - microbiology; Sanitizers; Spinach; Spinacia oleracea - microbiology; Vacuum; Vegetables
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-023-36815-9

Bacteriophage and gaseous ozone are evolving as meritorious alternatives to conventional sanitizers in food postharvest applications. Here, we investigated the efficacy of sequential treatments of a lytic bacteriophage and gaseous ozone, during vacuum cooling of fresh produce, against Escherichia coli O157:H7. Spinach leaves were spot-inoculated with 10 -10  CFU g E. coli O157:H7 B6-914 and treated with Escherichia phage OSYSP spray (10 PFU g ), gaseous ozone, or their combination. Vacuum cooling, which preceded or followed phage application but ran concomitantly with ozone treatment, was performed in a custom-made vessel at the following process sequence: vacuum to 28.5 in. Hg, vessel pressurization to 10 psig with gas containing 1.5 g ozone/kg gas-mix, holding for 30 min, and vessel depressurization to ambient pressure. Bacteriophage or gaseous ozone inactivated E. coli O157:H7, applied at different initial populations on spinach leaves, by 1.7-2.0 or 1.8-3.5 log CFU g , respectively. At the high inoculum levels tested (7.1 log CFU g ), sequential treatments of phage and ozone reduced E. coli O157:H7 population by 4.0 log CFU g , but when treatment order was reversed (i.e., ozone followed by bacteriophage), the combination synergistically decreased pathogen's population on spinach leaves by 5.2 log CFU g . Regardless the antibacterial application order, E. coli O157:H7 populations, applied initially at ~ 10  CFU g , were reduced below the enumeration method's detection level (i.e., < 10  CFU g ). The study proved that bacteriophage-ozone combination, applied in conjunction with vacuum cooling, is a potent pathogen intervention strategy in fresh produce post-harvest applications.