Sensitivity of wild-type and rifampicin-resistant O157 and non-O157 Shiga toxin-producing Escherichia coli to elevated hydrostatic pressure and lactic acid in ground meat and meat homogenate

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.

Public Health Importance of Preventive Measures for Salmonella Tennessee and Salmonella Typhimurium Strain LT2 Biofilms

“…The later comparisons were achieved using a Dunnett's-adjusted ANOVA, and in the graphs, these analyses were presented using the "*" sign to indicate a statistical difference (p < 0.05) from the untreated control (Figures 1 and 2). These analyses were conducted on data collected from the selective medium for Salmonella serovars (e.g., XLD agar) and non-selective medium supplemented with yeast extract to ensure maximum recovery of injured cells [33,38]. In addition to these, the pathogen log reductions were presented for selective and non-selective media to afford the opportunity for side-by-side comparisons of the three treatments with the untreated control (Figure 3A,B).…”

Synergistic Effects of Nisin, Lysozyme, Lactic Acid, and CitricidalTM for Enhancing Pressure-Based Inactivation of Bacillus amyloliquefaciens, Geobacillus stearothermophilus, and Bacillus atrophaeus Endospores

“…These results indicate that lactic acid could, to great extent, augment the decontamination efficacy of the treatment against the endospore of these three indicator microorganisms and most importantly against G. stearothermophilus that exhibited very high resistance to elevated hydrostatic pressure treatments (Figure 2A,B). Lactic acid is a very common antimicrobial in food commerce; it has been tested against an array of pathogenic microorganisms and is the dominant antimicrobial of choice in North America's meat industry [17]. This antimicrobial is also part of the recommendation of regulatory agencies, such as the World Health Organization, to improve the microbiological properties of food products [50].…”

“…Among various emerging technologies, the application of elevated hydrostatic pressure or high-pressure processing is gaining increasing importance and momentum [15,16]. Although the use of elevated hydrostatic pressure for the inactivation of microorganisms was proposed more than a century ago, in recent years, due to advancements in commercially available pressure-based pasteurizers, this technology is becoming an important part of food commerce [17,18]. High-pressure processing exposes the final packaged products to pressure intensity levels of typically around 650 MPa for durations lasting typically around three minutes [19][20][21].…”