Abstract
Various serogroups of Shiga toxin-producing Escherichia coli have been epidemiologically associated with foodborne disease episodes in the United States and around the globe, with E. coli O157: H7 as the dominant serogroup of public health concern. Serogroups other than O157 are currently associated with about 60% of Shiga toxin-producing E. coli related foodborne illness episodes. Current study evaluated sensitivity of the O157 and epidemiologically important non-O157 serogroups of the pathogen to elevated hydrostatic pressure and 1% lactic acid. Pressure intensity of 250 to 650 MPa were applied for 0 to 7 min for inactivation of strain mixtures of wild-type and rifampicin-resistant E. coli O157, as well as O26, O45, O103, O111, O121, and O145 serogroups and ATCC® 43895™ strain in ground meat and 10% meat homogenate. E. coli O157 were reduced (p < 0.05) from 6.86 ± 0.2 to 4.56 ± 0.1 log CFU/g when exposed to pressure of 650 MPa for 7 min. Corresponding reductions (p < 0.05) for non-O157 E. coli were from 6.98 ± 0.3 to 4.72 ± 0.1. The D-values at 650 MPa were 3.71 and 3.47 min for O157 and non-O157 serogroups, respectively. Presence of 1% lactic acid to a great extent augmented (p < 0.05) decontamination efficacy of the treatment in meat homogenate resulting in up to 5.6 and 6.0 log CFU/mL reductions for O157 and non-O157 serogroups, respectively. Among the tested serogroups, the wild-type and rifampicin-resistant phenotypes exhibited (p ≥ 0.05) comparable pressure sensitivity. Thus, these two phenotypes could be used interchangeably in validation studies. Our results also illustrate that, application of elevated hydrostatic pressure could be utilized for assuring safety of ground and non-intact meat products against various serogroups of Shiga toxin-producing E. coli. Addition of 1% lactic acid additionally provided industrially appreciable augmentation in efficacy of the pressure-based treatments.
Highlights
While vast majority of Escherichia coli serovars are commensal microorganisms and do not pose any health risk, a small subgroup of this bacterium could cause intestinal and extraintestinal infections in humans
For the study conducted in ground meat, samples were exposed to three levels of elevated hydrostatic pressure (650, 450, and 250 MPa)
For the experiments conducted in meat homogenate, samples were treated for 0, 2, 5, and 7 min at 350 MPa with or without presence of 1% lactic acid
Summary
While vast majority of Escherichia coli serovars are commensal microorganisms and do not pose any health risk, a small subgroup of this bacterium could cause intestinal and extraintestinal infections in humans. Among pathogenic E. coli, there were historically six well-defined pathotypes [1]. An outbreak of E. coli O104: H4 that simultaneously exhibited characteristics of two previously characterized pathotypes, and advancements in molecular subtyping had blurred the boundaries among these six categories of pathogenic E. coli [2, 3], making nomenclature of pathogenic E. coli a complex and evolving matter. Vast majority of foodborne burden associated with this pathogen is associated with Enterohaemorrhagic E. coli (EHEC) pathotype. Many of the serogroups belonging to this pathotype are capable of encoding/excreting Shiga toxins and causing hemorrhagic colitis. In high risk cases, they could cause a potentially fatal kidney complication in form of hemolytic uremic syndrome [1]
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