Survival or Growth of Escherichia coli O157:H7 in a Model System of Fresh Meat Decontamination Runoff Waste Fluids and Its Resistance to Subsequent Lactic Acid Stress

Abstract

A potential may exist for survival of and resistance development by Escherichia coli O157:H7 in environmental niches of meat plants applying carcass decontamination interventions. This study evaluated (i) survival or growth of acid-adapted and nonadapted E. coli O157:H7 strain ATCC 43895 in acetic acid (pH 3.6 ؎ 0.1) or in water (pH 7.2 ؎ 0.2) fresh beef decontamination runoff fluids (washings) stored at 4, 10, 15, or 25°C and (ii) resistance of cells recovered from the washings after 2 or 7 days of storage to a subsequent lactic acid (pH 3.5) stress. Corresponding cultures in sterile saline or in heat-sterilized water washings were used as controls. In acetic acid washings, acid-adapted cultures survived better than nonadapted cultures, with survival being greatest at 4°C and lowest at 25°C. The pathogen survived without growth in water washings at 4 and 10°C, while it grew by 0.8 to 2.7 log cycles at 15 and 25°C, and more in the absence of natural flora. E. coli O157:H7 cells habituated without growth in water washings at 4 or 10°C were the most sensitive to pH 3.5, while cells grown in water washings at 15 or 25°C were relatively the most resistant, irrespective of previous acid adaptation. Resistance to pH 3.5 of E. coli O157:H7 cells habituated in acetic acid washings for 7 days increased in the order 15°C > 10°C > 4°C, while at 25°C cells died off. These results indicate that growth inhibition by storage at low temperatures may be more important than competition by natural flora in inducing acid sensitization of E. coli O157:H7 in fresh meat environments. At ambient temperatures in meat plants, E. coli O157:H7 may grow to restore acid resistance, unless acid interventions are applied to inhibit growth and minimize survival of the pathogen. Acid-habituated E. coli O157:H7 at 10 to 15°C may maintain a higher acid resistance than when acid habituated at 4°C. These responses should be evaluated with fresh meat and may be useful for the optimization of decontamination programs and postdecontamination conditions of meat handling.Escherichia coli O157:H7 has become the primary target organism of food animal carcass decontamination interventions, which are of increasing commercial use in North America (3,13,21,39,41). In-plant applications have shown effectiveness of decontamination in reducing the percentage of carcass samples being E. coli O157:H7 positive from preevisceration to postprocessing (2, 19). However, there is a need to evaluate the potential for development of acid resistance in E. coli O157:H7 during application of acid decontamination interventions in meat (31). Studies have shown that the pathogen may survive decontamination of meat with lactic or acetic acid (7,16,17), suggesting that survivors can exist and may potentially adapt to the residual organic acid in situ in commercial meat processing environments (31).Berry and Cutter (6) demonstrated that previous acid adaptation of E. coli O157:H7 by culturing in media with 1% glucose (9) reduced the effectiveness of a 2% acetic acid solution to ina...

Reductions of Shiga Toxin–Producing Escherichia coli and Salmonella Typhimurium on Beef Trim by Lactic Acid, Levulinic Acid, and Sodium Dodecyl Sulfate Treatments

“…Studies have shown that acid application can reduce the populations of aerobic bacteria, fecal coliforms, and E. coli (16). However, the efficacy of such methods has been in doubt since the recognition of acid-tolerant E. coli 0157:H7 (4,15,21,24). Our pure culture studies found that the bactericidal effects of 3% lactic acid for the inactivation of different STEC isolates were variable, with reduction ranging from 0.3 to 3.0 log CFU/ml within 2 min at 21°C.…”

“…Second, immersing beef in the treatment solution followed by rubbing (hand massaging) was more effective than immersion only, and immersion only was better than a surface spray application for reducing STEC on beef surfaces. Third, STEC may survive in acid-based treatment solutions, and acid-tolerant STEC may recover in the treatment solution following application (24). However, STEC does not survive in levulinic acid plus SDS solution, thereby mitigating the possibility of STEC contamination in fluid remaining after treatment application.…”

“…Previous studies revealed that resistance of all isolates of E. coli 0157:H7 cells to pH 3.5 preconditioned in acetic acid washings was temperature related, e.g" for 7 days, it increased in the order 15°C >10°C > 4°C, whereas at 25°C cells died off (24). All of the STEC isolates evaluated were sensitive to 0.5% levulinic acid plus 0.05% SDS, with cell populations reduced by > 5 log CFU/ml within 1 min.…”

“…All of the STEC isolates evaluated were sensitive to 0.5% levulinic acid plus 0.05% SDS, with cell populations reduced by > 5 log CFU/ml within 1 min. Samelis et al (24) observed that at ambient temperature in meat plants, E. coli 0157:H7 may grow to restore acid resistance, unless acid interventions are applied to inhibit growth or kill the pathogen.…”

Practical and Novel Sterilization Approach for the Pathogenic Staphylococcus aureus Bacteria

“…The surface pH of samples was measured by using flat probe pH meter (Prescisa, Switzerland) on 0, 2nd, 6th and 12th days of storage. At this step, each piece of meat (10 g) was aseptically blended with 90 mL of sterile peptone water (Merck, Germany) in a laboratory blender [15] . After that, 1 mL of the blended sample of each inoculated meat with S. aureus was transferred onto Petri dishes for pour plate culturing with standard plate count agar (Merck, Germany) individually.…”