Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2015
Publication Date: 7/7/2015
Citation: Sheen, S., Cassidy, J.M., Scullen, O.J., Sommers, C.H. 2015. Inactivation of a diverse set of shiga toxin-producing Escherichia coli in ground beef by high pressure processing. Food Microbiology. 52:84-87.
Interpretive Summary: Shiga Toxin-Producing Escherichia coli (STEC) are common contaminants in ground beef and cause illness foodborne illness outbreaks. High pressure processing (HPP) is a green and sustainable alternative nonthermal processing technology that kills bacteria in foods and does not require the use of added chemicals or water. In this study we determined the D-10 value (the dose needed to kill 90% of a microorganism) for 39 STEC isolates which carried various combinations of genes necessary to cause illness in humans. The presence or absence of virulence factors (e.g. shiga toxin 1 or 2, intimin, or enterohemolysin) had no significant effect on the STEC HPP D-10. The D-10 of the STEC ranged from 0.89 to 25.7 min at a pressure of 350 MPa. The high D-10 (e.g. 25.7 min) of some STEC involved in human illness should be considered in selecting HPP processing parameters for treating ground beef. The results of this study will allow regulatory agencies and the high pressure and food processing industries to conduct risk analysis and provide safer meat to consumers. Consumers, especially those who are immuno-compromised (e.g. cancer patients, diabetics, and the HIV/AIDS population) will benefit from having more information about foods treated with alternative processes which kill harmful bacteria such as the STEC.
Technical Abstract: Shiga Toxin-Producing Escherichia coli (STEC) are frequently implicated in foodborne illness outbreaks and recalls of ground beef. In this study we determined the High Pressure Processing (HPP) D-10 value (the processing conditions needed to reduce the microbial population by 1 log) of 39 individual STEC isolates, including the “big six” serovars, O104 and O157:H7, etc. STEC isolates included those isolated from animals and environmental sources in addition to those associated with illness in humans. Individual STEC were inoculated into 80 percent lean ground beef and treated with HPP (at 350 MPa, 4 degree C, 0 - 40 min). The mean D-10 was 9.74 min, with a range of 0.89 to 25.70 min. The D-10 of the STEC involved in human illness was 9.25 vs. 10.40 min for those not involved in human illness (p > 0.05). The presence or absence of virulence factors (e.g. shiga toxin 1 or 2, intimin, or enterohemolysin) had little effect on the HPP D-10 (p > 0.05). The high D-10 of some STEC involved in human illness should be considered in selecting HPP processing parameters for ground beef. This study has demonstrated the heterogeneity of STEC resistance to HPP stress. Risk assessors and the food industry can use this information to provide safer meat products to consumers.