Ineffectiveness of Hot Acid Sprays to Decontaminate Escherichia coli O157:H7 on Beef

Abstract

The efficacy of warm (20°C) and hot (55°C) acetic, citric and lactic acid sprays on survival of Escherichia coli O157:H7 on raw beef was determined. Fresh, raw beef sirloin tips were sliced into ca. 1-cm slices with a sanitized slicer. Discs (5-cm diameter, ca. 25-g) were then taken from internal areas of each slice and inoculated with a 5-strain mixture of E. coli O157:H7 such that final populations on beef samples were 103 or 106 CFU/g. After standing for 15 min, each inoculated disc was sprayed with 1 mi of 0, 0.5, 1.0 and 1.5% of each acid at 20 or 55°C using an atomizer. Acid-treated meat samples were allowed to dry for 15 min and held at 5°C for up to 13 days in sterile plastic pouches. Escherichia coli O157:H7 was acid tolerant, and acids did not differ appreciably in their lack of antimicrobial activity on E. coli O157:H7. For example, reductions in populations differed by <0.3 logl0 CFU/g immediately after treatment and < 0.5 logl0 CFU/g after 13 days incubation, compared to untreated Controls. None of the acid treatments appreciably reduced E. coli O157:H7 on beef samples nor were any of the acid treatments judged effective for practical uses.

Inactivation of Enterohemorrhagic Escherichia coli in Rumen Content- or Feces-Contaminated Drinking Water for Cattle

“…Several studies have revealed that application of organic acids, such as acetic, citric, and lactic acids, does not substantially reduce E. coli O157:H7 cell numbers in food, which may be explained by the exceptional acid tolerance of many strains of E. coli O157:H7 (6,8,16,31,33,34). For example, Brackett et al (8) evaluated the efficacies of warm (20°C) and hot (55°C) acetic, citric, and lactic acid sprays on the survival of E. coli O157:H7 on raw beef and determined that none of the acid treatments appreciably reduced E. coli O157:H7 on beef samples, nor were any of the acid treatments judged effective for practical uses.…”

“…For example, Brackett et al (8) evaluated the efficacies of warm (20°C) and hot (55°C) acetic, citric, and lactic acid sprays on the survival of E. coli O157:H7 on raw beef and determined that none of the acid treatments appreciably reduced E. coli O157:H7 on beef samples, nor were any of the acid treatments judged effective for practical uses. Glass et al (16) studied the influence of pH adjusted with lactic acid or HCl on survival or growth of E. coli O157:H7 in tryptic soy broth and determined that the organism could grow in TSB at pH 4.5 to 9.0, adjusted with HCl.…”

Adaptation of Escherichia coli O157:H7 to pH Alters Membrane Lipid Composition, Verotoxin Secretion, and Resistance to Simulated Gastric Fluid Acid

“…However, Brackett et al (7) reported that hot acid sprays did not control E. coli O157:H7 on raw beef, which suggests that adaptation of surviving E. coli O157:H7 to acid may occur during the rinsing of animal carcasses with acid and the subsequent storage period. Consequently, improper cooking of beef contaminated by acidadapted cells may increase the risk of illness.…”

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

“…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 inactivate it on decontaminated beef. Recent studies from our laboratory have used meat decontamination runoff waste fluids of different pHs (acidic, acid-diluted, or nonacid-water spray washings) as a model system to evaluate responses of E. coli O157:H7 under conditions simulating those in meat plant environments (33,34,35,37,42).…”

“…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).…”