Evaluation of peroxyacetic acid as a post-chilling intervention for control of Escherichia coli O157:H7 and Salmonella Typhimurium on beef carcass surfaces

Antimicrobial efficacy of a citric acid/hydrochloric acid blend, peroxyacetic acid, and sulfuric acid against Salmonella and background microbiota on chicken hearts and livers

This study aimed at evaluating the efficacy of a blend of citric acid and hydrochloric acid (CP), peroxyacetic acid (PAA), and sulfuric acid (SA) against Salmonella and mesophilic aerobic plate counts (APC) on chicken hearts and livers. Samples were inoculated with a five-serovar cocktail of Salmonella at ca. 4.8 log CFU/g and treated by immersion with a water control (90 s), CP (5% v/v, 30 s), PAA (0.05% v/v or 500 ppm, 90 s), or SA (2% v/v, 30 s), all at 4°C and with mechanical agitation. Samples were vacuum packed and stored for up to 3 days at 4°C. Three independent replications were performed for each product, treatment, and time combination. The average Salmonella reductions in chicken hearts after 3 days were 1.33 ± 0.25, 1.40 ± 0.04, and 1.32 ± 0.12 log CFU/g for PAA, SA, and CP, respectively. For chicken livers, the values were 1.10 ± 0.12, 1.09 ± 0.19, and 0.96 ± 0.27 for PAA, SA, and CP, respectively. All antimicrobials reduced Salmonella counts in both chicken hearts and livers by more than one log, in contrast to the water control. All treatments effectively minimized the growth of APC for up to 3 days of refrigerated storage, and no differences in objective color values (L, a, or b) were observed. The poultry industry may use these antimicrobials as components of a multifaceted approach to mitigate Salmonella in nonconventional chicken parts.

Antimicrobial Tolerance in Salmonella: Contributions to Survival and Persistence in Processing Environments

Salmonella remains a top bacterial pathogen implicated in several food-borne outbreaks, despite the use of antimicrobials and sanitizers during production and processing. While these chemicals have been effective, Salmonella has shown the ability to survive and persist in poultry processing environments. This can be credited to its microbial ability to adapt and develop/acquire tolerance and/or resistance to different antimicrobial agents including oxidizers, acids (organic and inorganic), phenols, and surfactants. Moreover, there are several factors in processing environments that can limit the efficacy of these antimicrobials, thus allowing survival and persistence. This mini-review examines the antimicrobial activity of common disinfectants/sanitizers used in poultry processing environments and the ability of Salmonella to respond with innate or acquired tolerance and survive exposure to persists in such environments. Instead of relying on a single antimicrobial agent, the right combination of different disinfectants needs to be developed to target multiple pathways within Salmonella.

Efficacy of Antimicrobial Spray Treatments in Reducing Salmonella enterica Populations on Chilled Pork

Studies reporting on alternative antimicrobial interventions for pathogen control on chilled pork carcasses and cuts are limited. In this study, the antimicrobial effects of various spray treatments against Salmonella enterica inoculated on skin-on pork samples were evaluated. Chilled pork jowls were portioned (10 by 5 by 1 cm) and inoculated, on the skin side, with a mixture of six S. enterica serotype strains to target levels of 6 to 7 log CFU/cm² (high inoculation level) or 3 to 4 log CFU/cm² (low inoculation level). Samples were then left nontreated (control) or were treated (10 s) using a laboratory-scale spray cabinet with water, formic acid (1.5%), a proprietary blend of sulfuric acid and sodium sulfate (SSS, pH 1.2), peroxyacetic acid (PAA, 400 ppm), or PAA (400 ppm) that was pH-adjusted (acidified) with acetic acid (1.5%), formic acid (1.5%), or SSS (pH 1.2). Samples (n = 6) were analyzed for Salmonella populations after treatment application (0 h) and after 24 h of refrigerated (4°C) storage. Irrespective of inoculation level, all spray treatments effectively reduced (P < 0.05) Salmonella levels immediately following their application. Overall, pathogen reductions for the chemical treatments, compared to the respective high and low inoculation level nontreated controls, ranged from 1.2 to 1.9 log CFU/cm² (high inoculation level) and 1.0 to 1.7 log CFU/cm² (low inoculation level). Acidification of PAA with acetic acid, formic acid, or SSS did not (P ≥ 0.05) enhance the initial bactericidal effects of the nonacidified PAA treatment. Salmonella populations recovered from all treated samples following 24 h of storage were, in general, similar (P ≥ 0.05) or up to 0.6 log CFU/cm² lower (P < 0.05) than those recovered from samples analyzed immediately after treatment application. The results of the study may be used by processing establishments to help identify effective decontamination interventions for reducing Salmonella contamination on pork.

Processing interventions for enhanced microbiological safety of beef carcasses and beef products: A review

Chilled beef is inevitably contaminated with microorganisms, starting from the very beginning of the slaughter line. A lot of studies have aimed to improve meat safety and extend the shelf life of chilled beef, of which some have focused on improving the decontamination effects using traditional decontamination interventions, and others have investigated newer technologies and methods, that offer greater energy efficiency, lower environmental impacts, and better assurances for the decontamination of beef carcasses and cuts. To inform industry, there is an urgent need to review these interventions, analyze the merits and demerits of each technology, and provide insight into 'best practice' to preserve microbial safety and beef quality. In this review, the strategies and procedures used to inhibit the growth of microorganisms on beef, from slaughter to storage, have been critiqued. Critical aspects, where there is a lack of data, have been highlighted to help guide future research. It is also acknowledge that different intervention programs for microbiological safety have different applications, dependent on the initial microbial load, the type of infrastructures, and different stages of beef processing.

Efficacy of Antimicrobial Interventions Used in Meat Processing Plants against Antimicrobial Tolerant Non-Antibiotic-Resistant and Antibiotic-Resistant Salmonella on Fresh Beef

ABSTRACT

Salmonella is a common cause of foodborne illness in the United States, and several strains of Salmonella have been identified as resistant to antibiotics. It is not known whether strains that are antibiotic resistant (ABR) and that have some tolerance to antimicrobial compounds are also able to resist the inactivation effects of antimicrobial interventions used in fresh meat processing. Sixty-eight Salmonella isolates (non-ABR and ABR strains) were treated with half concentrations of lactic acid (LA), peracetic acid (PAA), and cetylpyridinium chloride (CPC), which are used in beef processing plants to screen for tolerant strains. Six strains each from non-ABR and ABR Salmonella that were most tolerant of LA (2%), PAA (200 ppm), and CPC (0.4%) were selected. Selected strains were inoculated on surfaces of fresh beef and subjected to spray wash treatment with 4% LA, 400 ppm PAA, or 0.8% CPC for the challenge study. Tissue samples were collected before and after each antimicrobial treatment for enumeration of survivors. Spray treatment with LA, PAA, or CPC significantly reduced non-ABR Salmonella and ABR Salmonella on surfaces of fresh beef by 1.95, 1.22, and 1.33 log CFU/cm2, and 2.14, 1.45, and 1.43 log CFU/cm2, respectively. The order of effectiveness was LA > PAA = CPC. The findings also indicated that LA, PAA, and CPC were equally (P ≤ 0.05) effective against non-ABR and ABR Salmonella on surfaces of fresh beef. These data contribute to the body of work that indicates that foodborne pathogens that have acquired both antibiotic resistance and antimicrobial tolerance are still equally susceptible to meat processing antimicrobial intervention treatments.

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Evaluation of the safety and efficacy of lactic acid to reduce microbiological surface contamination on carcases from kangaroos, wild pigs, goats and sheep

Studies evaluating the safety and efficacy of lactic acid to reduce microbiological surface contamination from carcases of wild game (i.e. kangaroos and wild pigs) and small stock (i.e. goats and sheep) before chilling at the slaughterhouse were assessed. Wild pig and kangaroo hide‐on carcases may have been chilled before they arrive at the slaughterhouse and are treated after removal of the hides. Lactic acid solutions (2–5%) are applied to the carcases at temperatures of up to 55°C by spraying or misting. The treatment lasts 6–7 s per carcass side. The Panel concluded that: [1] the treatment is of no safety concern, provided that the lactic acid complies with the European Union specifications for food additives; [2] based on the available evidence, it was not possible to conclude on the efficacy of spraying or misting lactic acid on kangaroo, wild pig, goats and sheep carcases; [3] treatment of the above‐mentioned carcases with lactic acid may induce reduced susceptibility to the same substance, but this can be minimised; there is currently no evidence that prior exposure of food‐borne pathogens to lactic acid leads to the occurrence of resistance levels that compromise antimicrobial therapy; and [4] the release of lactic acid is not of concern for the environment, assuming that wastewaters released by the slaughterhouses are treated on‐site, if necessary, to counter the potentially low pH caused by lactic acid, in compliance with local rules.

Validation of Commonly Used Antimicrobial Interventions on Bob Veal Carcasses for Reducing Shiga Toxin-Producing Escherichia coli Surrogate Populations

ABSTRACT

Ruminants are natural reservoirs of Shiga toxin-producing Escherichia coli (STEC), and the STEC can be easily transferred to carcasses during the conversion of animals to meat. Three experiments were conducted to validate the efficacy of lactic acid (LA; 4%), peroxyacetic acid (PAA; 300 ppm), and hot water (HW; 80°C) for their individual or combined abilities to reduce STEC surrogates on bob veal carcasses pre- and postchill and through fabrication. In experiment 1, hot carcasses (n = 9) were inoculated with a five-strain cocktail (ca. 8 log CFU/mL) containing rifampin-resistant surrogate E. coli (BAA-1427, BAA-1428, BAA-1429, BAA-1430, and BAA-1431) and then treated with HW, LA, or PAA. Carcasses were then chilled (0 ± 1°C; 24 h) and split in half, and each side was treated with either LA or PAA. In experiment 2, hot carcasses (n = 3) were inoculated and chilled (24 h). After 24 h, the carcasses were split, and each side was treated with either LA or PAA. For experiment 3, carcasses (n = 3) were chilled for 24 h, split, inoculated, and treated with either LA or PAA. After chilling, carcasses from all three experiments were fabricated to subprimals and the cut surfaces were sampled to determine the translocation of bacteria. Experiment 1 showed that LA+LA was the most effective (P ≤ 0.05) treatment for reducing surrogate E. coli on veal. In experiments 2 and 3, LA and PAA were similar (P > 0.05) in their abilities to reduce E. coli on chilled veal carcasses. In experiments 1 and 2, all antimicrobial treatments resulted in undetectable levels (<0.2 log CFU/cm2) of surrogate E. coli on cut surfaces after fabrication, whereas low levels (1.7 and 1.0 log CFU/cm2 for LA and PAA, respectively) were observed in experiment 3. Of the antimicrobial interventions utilized, LA was more effective for reducing STEC surrogate populations on veal carcasses, pre- and/or postchill.

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Effects of Peroxyacetic Acid Spray and Storage Temperature on the Microbiota and Sensory Properties of Vacuum-Packed Subprimal Cuts of Meat

We investigated the impact of peroxyacetic acid (PAA; 200 ppm) spray on the microbiota and shelf life of commercial, vacuum-packed beef stored at chiller temperatures. Ribeye cuts (n = 147) were collected from a local beef plant on the day of production for two consecutive days, with one set collected at the start of work with the PAA spray nozzles turned off (control) and during routine production with the PAA spray nozzles turned on (PAA) each day. Packs were stored at 4, 2, and -1°C for up to 34, 104, and 180 days and sampled at appropriate intervals for sensory assessment, microbial enumeration, and microbial profiling by 16S rRNA gene amplicon analysis. Treatment with PAA did not affect the initial meat pH, the initial numbers of total aerobes, lactic acid bacteria, or Enterobacteriaceae (P > 0.05) before storage; however, it delayed the onset of spoilage by 7, 21, and 54 days at 4, 2, and -1°C, respectively. Square-root models of the variation of growth rate with temperature indicated lactic acid bacteria grew faster and Enterobacteriaceae grew slower on PAA-treated than on untreated meat. Negative associations between pH and deterioration of meat during storage were observed for PAA-treated meat. During storage, the microbiota were primarily dominated by Carnobacterium and Lactobacillus/Lactococcus on control meat but by Leuconostoc on PAA-treated meat. Serratia, Yersinia, and Clostridium were identified by linear discriminant effect size analysis as biomarkers for control meat; Clostridium was found in high abundance in samples that had the highest spoilage scores.IMPORTANCE The findings of this study show that PAA solutions applied at low concentrations under commercial settings positively modulated the meat microbiota. It did not have bactericidal effects for beef subprimals with very low microbial loads. However, it differentially impacted the members of the microbiota, which resulted in delayed onset of spoilage of vacuum-packed beef subprimal stored at all three temperatures (4, 2, and -1°C). This differential impact could be through one or a combination of the following factors: favoring the growth of lactic acid bacteria, which may in turn exert a competitive exclusion that might be due to production of antimicrobial compounds such as organic acids and bacteriocins; exerting synergistic antimicrobial effects with low temperatures against members of Enterobacteriaceae; and direct or indirect inhibitory effects against members of the clostridia. These findings not only advance our understanding of the microbial ecology of vacuum-packed meat stored at chiller temperatures but also suggest that bacteriostatic concentrations of antimicrobial interventions can be explored for shelf-life extension.

Antimicrobial Efficacy of Acidified Peroxyacetic Acid Treatments Against Surrogates for Enteric Pathogens on Prerigor Beef

Two studies were conducted to evaluate the antimicrobial effects of pH-adjusted solutions of peroxyacetic acid (PAA) against nonpathogenic Escherichia coli surrogates for Shiga toxin–producing E. coli and Salmonella, inoculated on beef. In both studies, prerigor beef carcass surface tissue (10 × 10 cm pieces) was inoculated (6–7 log colony-forming units [CFU]/cm2) on the adipose side with a 5-strain mixture of E. coli biotype I. In the first study, samples were left untreated (control) or were immersed (10 s) in solutions of PAA (300 parts per million [ppm]) acidified with a sulfuric acid and sodium sulfate blend (SSS) (pH 1.2) or PAA (400 ppm) acidified with acetic acid (2%), citric acid (1%), lactic acid (3.5%), or SSS (pH 1.2 or pH 1.8). In the second study, samples were left untreated or were spray treated (10 s) using a spray cabinet, with water, PAA (350 ppm or 400 ppm), PAA (350 ppm or 400 ppm) acidified with SSS (pH 1.2), or PAA (400 ppm) acidified with acetic acid (2%). All immersion treatments effectively (P &lt; 0.05) reduced inoculated E. coli populations (6.2 log CFU/cm2) by 2.3 to 2.8 log CFU/cm2. When the test solutions were applied by spraying, the water and all PAA-containing treatments lowered inoculated populations (6.4 log CFU/cm2) by 0.4 (P ≥ 0.05) and 1.7–1.9 (P &lt; 0.05) log CFU/cm2, respectively. No (P ≥ 0.05) differences in decontamination efficacy were observed between the 5 PAA-containing spray treatments. Overall, the results showed that PAA and the pH-adjusted PAA treatments were effective in reducing levels of the surrogates for Shiga toxin–producing E. coli and Salmonella. Although no differences in antimicrobial efficacy were noted between the nonacidified and acidified PAA treatments immediately after treatment application, further studies are needed to evaluate how the acidified PAA treatments perform as part of a sequential multi-hurdle decontamination strategy to reduce pathogen contamination on beef carcasses.

Efficacy of peroxy acetic acid in reducing Salmonella and Campylobacter spp. populations on chicken breast fillets

Poultry processors use antimicrobials to reduce the risk of pathogens on poultry and poultry products. The efficacy of selective and nonselective plating media to enumerate injured Salmonella (selective media-brilliant green sulfa agar and Petrifilm Enterobacteriaceae Plate Count; nonselective media-tryptic soy agar and Petrifilm Aerobic Plate Count) and Campylobacter (selective medium-Campy cefex agar and nonselective medium-Brucella agar) populations and the efficacy of peroxy acetic acid (PAA) to reduce Salmonella and Campylobacter populations on chicken breast fillets were evaluated. All plating media for Salmonella and Campylobacter contained nalidixic acid (200 ppm) or gentamycin (200 ppm), respectively. Breast fillets were sprayed or immersed in PAA (500 ppm) for 10 min for evaluation of the plating media. Breast fillets inoculated with a mixed Salmonella and Campylobacter cocktail were sprayed (5 or 10 s) or immersed (4-30 s) in PAA (100, 400, 500, or 1,000 ppm) for evaluation of PAA efficacy. Salmonella populations were higher (P ≤ 0.05) when plated on nonselective media compared with the selective media for the non-PAA treated fillets, although the differences in populations were low (<0.32 log CFU/mL). For both the microorganisms, populations on PAA treated (immersion or spray) fillets were similar when enumerated on nonselective or selective media within each treatment (PAA immersion or spray). Both immersion and spray applications reduced (P ≤ 0.05) the Salmonella and Campylobacter populations compared with the control. Increasing the PAA concentration to 250, 500, and 1,000 ppm resulted in greater reductions (P ≤ 0.05) in Salmonella and Campylobacter populations. Immersion of the inoculated breast fillets in 1,000 ppm PAA solution for 30 s resulted in Salmonella and Campylobacter population reductions of 1.92 and 1.87 log CFU/mL, respectively. Method of antimicrobial application (immersion and spray) did not affect the reductions in Salmonella and Campylobacter populations. Either immersion or spray application can be used to improve microbial safety of chicken breast fillets in a poultry processing plant.

Efficacy of bacteriophage and organic acids in decreasing STEC O157:H7 populations in beef kept under vacuum and aerobic conditions: A simulated High Event Period scenario

After High Event Periods, beef subprimals are usually removed from vacuum and treated with antimicrobials. After re-packaging, subprimals are tested to verify the presence of STEC. In this study, bacteriophage and organic acids were applied on beef contaminated with STEC O157:H7 to evaluate the efficiency of industry practices. Beef samples inoculated with STEC were treated with bacteriophage, lactic acid, and peroxyacetic acid and kept under vacuum or aerobic conditions. STEC loads were evaluated 30 min and 6 h after antimicrobial applications. Under aerobic conditions for 30 min and 6 h, phage reduced STEC in beef by approximately 1.4 log whereas organic acids led to a 0.5 log reduction. Under vacuum for 30 min, bacteriophage significantly reduced STEC by 1 log. No effects were observed when samples were treated with organic acids. Under vacuum after 6 h, bacteriophage reduced STEC loads by 1.4 log, lactic acid reduced by 0.6 log, and no effects were observed when peroxyacetic acid was applied.

Sustainability of safe foods: Joint environmental, economic and microbial load reduction assessment of antimicrobial systems in U.S. beef processing

Various antimicrobial interventions are applied sequentially in the beef processing industry to reduce microbial load on beef products by using intensive inputs (e.g., chemicals, energy), high strength wastewater, and potentially result in meat discoloration. This study serves as the first analysis to jointly evaluate environmental and economic assessment with its microbial load reduction of proposed antimicrobial systems in the U.S. beef processing industry to identify relatively sustainable systems that minimize environmental and economic impacts while providing microbial safe meat. Specifically, forty potential sequential antimicrobial systems were proposed and evaluated from three perspectives: microbial load reduction, environmental, and economic impacts, by meta-analysis, life cycle assessment, and operational cost analysis orderly. The results show that the antimicrobial systems applying steam pasteurization during the main intervention offer high microbial load reduction (>4.2 log CFU/cm² reduction from a hypothetical initial contamination at 5.0 log CFU/cm²). Human health impact (31.0 to 65.6%) and ecosystem toxicity (3.6 to 12.5%), eutrophication (11.9 to 15.5%) and global warming (6.4 to 22.2%) are the main contributors to the overall environmental single score among the forty antimicrobial systems. Antimicrobial chemicals (up to 82.8%), wastewater treatment (up to 12.7%), and natural gas (up to 10.7%) are the three major drivers of operational cost for sanitizing 1000 kg hot standard carcass weight (HSCW). Devalued (discolored) meat due to contact with heat from steam pasteurization or hot water wash has a considerable increase in economic ($4.5/1000 HSCW) and environmental (especially at farm stage) impacts. Certain antimicrobial systems (e.g., water wash followed by steam pasteurization) were found to be more promising with satisfactory effectiveness, better environmental and cost performance under uncertainty (1000 Monte Carlo simulations). Results from this study can guide the U.S. beef processing industry to advance sustainability while protecting human health from foodborne illness.

A Novel Aqueous Ozone Treatment as a Spray Chill Intervention against Escherichia coli O157:H7 on Surfaces of Fresh Beef

This experiment determined the efficacy of using a novel aqueous ozone treatment as a spray chill intervention to reduce Escherichia coli O157:H7 on surfaces of fresh beef compared with traditional water spray chill. Cutaneous trunci muscles were obtained from a local beef cattle processing plant. Muscles were divided into sixteen 25-cm² sections, and each section was individually inoculated with E. coli O157:H7 to the final concentration of approximately 10⁵ CFU/cm². Muscle sections were collected and tested before and after simulated spray chill treatments of water or the novel aqueous ozone solution. Enumeration of survivors of each treatment was compared with that of the untreated muscle sections. Water spray chill reduced (P ≤ 0.05) E. coli O157:H7 0.60 log, whereas the aqueous ozone spray chill reduction (P ≤ 0.05) was 1.46 log on surfaces of fresh beef. Aqueous ozone spray chill reduced (P ≤ 0.05) aerobic bacteria 0.99 log, but water spray chill did not significantly (P > 0.05) reduce aerobic bacteria on surfaces of fresh beef. The findings indicate that aqueous ozone can be used as a spray chill intervention to enhance the safety of beef.

Application of chlorine dioxide and peroxyacetic acid during spray chilling as a potential antimicrobial intervention for beef carcasses

Enteric pathogens such as Shiga-toxin producing Escherichia coli (STEC) and Salmonella spp. continue to be a major food safety concern for the beef industry. Currently, no single method is completely effective in controlling these pathogens during carcass processing. Previous research, however, suggested that STEC might become more susceptible to oxidative damage when exposed to carcass chilling (King et al., 2016). We aimed to test that hypothesis by evaluating the antimicrobial effects of an oxidant (chlorine dioxide, ClO₂ or peroxyacetic acid, PAA) on beef meat during a simulated spray chilling process (sprayed for 4 s every 15 min for 36 cycles) and/or when applied (sprayed for 144 s) prior to spray chilling with water. In all experiments, the inactivating effects of oxidants were greatest on fat surfaces and much less effective on lean surfaces. ClO₂ at 15 ppm, a non-lethal level for E. coli under optimal growth conditions, caused higher log reductions in E. coli numbers (approximately 3-log reduction) when applied during spray chilling than when applied immediately prior to 'normal' spray chilling (approximately 1-log reduction). This confirms the hypothesis that E. coli are more susceptible to oxidative stress during spray chilling. In subsequent studies, both ClO₂ and PAA at lethal levels (at ≥20 and ≥ 200 ppm, respectively) applied during spray chilling resulted in pronounced inactivation of both E. coli and Salmonella enterica strains, achieving a ≥4-log reduction at the end of chilling. These results indicate that an oxidant-based application during spray chilling as an antimicrobial intervention could be effective to minimise the problems associated with enteric pathogen contamination on beef meat.

Enhanced Efficacy of Peroxyacetic Acid Against Listeria monocytogenes on Fresh Apples at Elevated Temperature

Peroxyacetic acid (PAA) is the most commonly used antimicrobial in spray bar antimicrobial treatment during fresh apple packing and processing. However, there are limited data regarding its practical efficacy against Listeria monocytogenes on fresh apples. This study evaluated the antimicrobial activity of PAA against L. monocytogenes on fresh apples applicable to current industry practice, and further examined practical parameters impacting its efficacy to maximize the biocidal effects. Apples were inoculated with a three-strain L. monocytogenes cocktail at ~6.0 Log₁₀ CFU/apple and then subjected to comparative antimicrobial treatments after 48 h post-inoculation. An 80 ppm PAA treatment, at 30-s and 2-min exposure, reduced L. monocytogenes on fresh apples by ~1.3 or 1.7 Log₁₀ CFU/apple, respectively. The anti-Listeria efficacy of PAA was not affected by the water hardness and pH of PAA solution, while it improved dramatically when applied at elevated temperature. A 2-min exposure of 80 ppm PAA at 43 and 46°C resulted in a 2.3 and 2.6 Log₁₀ CFU/apple reduction, respectively. A 30-s contact time of 80 ppm PAA at 43-46°C reduced L. monocytogenes on apples by 2.2-2.4 Log₁₀ CFU/apple. Similarly, PAA intervention at elevated temperatures significantly strengthened its effectiveness against naturally occurring apple microbiota. PAA treatment at 43-46°C can provide a vital method to improve antimicrobial efficacy against both L. monocytogenes and indigenous microbiota on fresh apples. Our data provide valuable information and reference points for the apple industry to further validate or verify process controls.

Comparison of Antimicrobial Treatments Applied via Conventional or Handheld Electrostatic Spray To Reduce Shiga Toxin-Producing Escherichia coli on Chilled Beef Outside Rounds

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We found no advantage in the use of electrostatic spray to reduce STEC8 on cold beef. Greatest reductions in STEC8 were achieved by lactic acid with conventional spray. Lauric arginate ester was the second best antimicrobial agent at reducing STEC8. Lactic acid reduced pH on the beef surface significantly. There was no effect of antimicrobial solution on temperature increase on beef outside rounds.

In-Plant Validation Study of Harvest Process Controls in Two Beef Processing Plants in Honduras

Imported meat in the United States can become a food safety hazard if proper food safety programs are not fully implemented in foreign meat processing plants. Thus, exporting countries' food safety inspection systems must be equivalent to the U.S. federal inspection system to become eligible to export meat to the United States. The objective of this study was to validate the beef harvest Hazard Analysis and Critical Control Points and food safety programs of two beef processing plants in Honduras operating under U.S. equivalency standards by evaluating the presence of Salmonella (plant A) and Shiga toxin-producing Escherichia coli (STEC; plant B) on hides. Additionally, evaluating pathogen transfer from hides to carcasses, as detected by preevisceration sampling, and the mitigation of transferred pathogens, by application of carcass spray interventions and determination of Salmonella presence in lymph nodes, was also conducted. In plant A, the presence of Salmonella on hides ( n = 30 of 687; 4.4%) was significantly greater ( P < 0.10) than on carcasses swabbed at preevisceration ( n = 7 of 687; 1.0%), after intervention ( n = 13 of 678; 1.9%), and in lymph nodes ( n = 14 of 691; 2.0%). In plant B, Salmonella was not detected on hide samples; therefore, data could not be used for validation of the harvest Hazard Analysis and Critical Control Points program. Alternatively, STEC presence on hides ( n = 21 of 85; 24.7%) was greater ( P < 0.10) than on carcasses at preevisceration ( n = 3 of 85; 3.5%) and after intervention ( n = 1 of 85; 1.2%). Pathogen presence in plant B did not differ ( P = 0.306) between carcasses in preevisceration and postintervention stages; both, however, were substantially low. Both plants' controls effectively reduced Salmonella and STEC presence in postintervention carcasses.

Photohydroionization Reduces Shiga Toxin-Producing Escherichia coli and Salmonella on Fresh Beef with Minimal Effects on Meat Quality

The photohydroionization (PHI) technology utilizes a combination of UV light and low-level oxidizers to produce antimicrobial action, and thus, is a potential intervention to control pathogen contamination on surface of fresh beef. The objectives of the study were 1) to evaluate the effect of PHI on reduction of selected Escherichia coli (E. coli) O157:H7, non-O157 Shiga toxin-producing E. coli (STEC; O26, O45, O103, O111, O121, O145), antimicrobial resistant (AMR) and non-AMR Salmonella strains inoculated on beef flanks, and 2) to evaluate the effect of PHI treatment on the lean color and lipid oxidation of beef during refrigerated storage. Inoculated beef flanks were exposed to PHI treatment for 0 (control), 15, 30, or 60 s at 4°C. Exposure to PHI for 15 s reduced (P ≤ 0.05) pathogens on the surface of fresh beef ranging from 0.3 to 0.9 log CFU/cm2. Increasing the exposure time to 60 s did not improve (P > 0.05) reductions over 15 s for the majority of the selected pathogens, but yielded pathogen reductions ranging from 0.5 to 1.1 log CFU/cm2. Over all storage times when beef samples were exposed to PHI for 75 s, no difference (P > 0.05) was detected on lean a* value (24.67 versus 24.95), of treated and control fresh beef tissues, respectively. The highest TBARS values after storage for 14 d at 4°C was 0.33 mg MDA/kg of meat indicating that no oxidative rancidity occurred for treated beef samples. The PHI technology with 15 to 75 s exposure time was effective in controlling STEC and Salmonella contaminated on surface of fresh beef without causing adverse effects on fresh beef quality while reducing water and energy use. Further study of PHI treatment parameters under commercial plant conditions and ultimate validation of those parameters will be necessary for commercial implementation.

Validation of Antimicrobial Interventions for Reducing Shiga Toxin-Producing Escherichia coli Surrogate Populations during Goat Slaughter and Carcass Chilling

Demand and consumption of goat meat is increasing in the United States due to an increase in ethnic populations that prefer goat meat. As ruminant animals, goats are known reservoirs for Shiga toxin-producing Escherichia coli (STEC) and proper handling, especially during slaughter, is imperative to reduce the likelihood of carcass and meat contamination. However, the majority of antimicrobial intervention studies during the slaughter of ruminant species have focused on beef, highlighting the need for validation studies targeting small ruminants, such as goats, during slaughter and chilling procedures. The objective of this research was to evaluate 4.5% lactic acid (LA; pH 2.1), peroxyacetic acid (PAA; 400 ppm; pH 4.7), a hydrochloric and citric acid blend (Citrilow [CL]; pH 1.2), 5% levulinic acid plus 0.5% sodium dodecyl sulfate (LVA+SDS; pH 2.60), and a nontreated control (CON) for their efficacy in reducing STEC surrogates and their effect on carcass color from slaughter through 24-h chill. Fifteen goat carcasses across three replications were inoculated with a five-strain cocktail (ca. 5 log CFU/cm² attachment), containing rifampin-resistant surrogate E. coli (BAA-1427, BAA-1428, BAA-1429, BAA-1430, and BAA-1431) and were randomly assigned to an antimicrobial treatment. Antimicrobials were applied prechill and 24 h postchill. Mean log reductions achieved after prechill treatment with LA, PAA, CL, and LVA+SDS were 2.00, 1.86, 2.26, and 1.90 log CFU/cm², respectively. Antimicrobial treatment after the 24-h chilling, resulted in additional reductions of surrogate E. coli by 0.99, 1.03, 1.94, and 0.47 log CFU/cm² for LA, PAA, CL, and LVA+SDS, respectively. Antimicrobial treatments did not impact goat carcass objective color (L* and a*), except for b*. The antimicrobials tested in this study were able to effectively reduce surrogate STEC populations during slaughter and subsequent chilling without compromising carcass color.

Effects of Cetylpyridinium Chloride and Peroxyacetic Acid Treatment of Broiler Frames on Salmonella Incidence and Mechanically Separated Chicken Quality

Mechanically separated chicken (MSC) has a high incidence of Salmonella since it is separated and homogenized from multiple broiler frames. In addition, limited research has been reported on the reduction of naturally contaminated Salmonella on chicken carcasses or chicken frames. Therefore, broiler frames were treated with antimicrobial solutions of 0.1% peroxyacetic acid (PAA) or 0.5% cetylpyridinium chloride with Citrilow (CPC) for contact times of 30, 60, 90, or 120 s and evaluated for their effectiveness at reducing the incidence of naturally contaminated Salmonella spp. on broiler frames and decreasing Salmonella counts on inoculated frames that were ground and sieved into MSC. Treatment times for PAA and CPC did not affect (P > 0.05) % incidence of Salmonella on naturally contaminated broiler frames. While CPC30 showed a greater % reduction in incidence (P < 0.05) than PAA30, CPC90 and CPC120 did not differ (P > 0.05) from PAA90 and PAA120. However, the CPC treatments imparted a greater decrease in incidence of Salmonella on frames than PAA. For inoculated frames, both antimicrobial treatments at all treatment times had fewer (P < 0.05) Salmonella counts in MSC than their controls. Treated MSC samples were evaluated for pH, color, cook loss and protein bind. On average, CPC treatments were lighter (CIE L*; P < 0.05) than PAA treatments, and PAA treatments were more red (CIE a*) and more yellow (CIE b*; P < 0.05) than CPC treatments. All treatments produced MSC with lesser hue values than their controls. Protein bind and cook loss results indicated that the PAA treatments had no significant impact on MSC quality. Frames that were treated with CPC for 60 s yielded less protein bind than the control, which indicates less protein functionality.

Evaluation of chlorine dioxide, acidified sodium chlorite and peroxyacetic acid for control of Escherichia coli O157:H7 in beef patties from treated beef trim

The effectiveness of 30 to 400ppm chlorine dioxide (CDO), acidified sodium chlorite (ASC) and peroxyacetic acid (PAA) to control Escherichia coli O157:H7 in beef was examined. Ground beef made from treated meat was vacuum packaged and stored at 4°C for 4d. CDO or ASC concentration by storage time interaction for inactivation of E. coli O157:H7 was significant (P<0.05). Exposure of beef to 200 and 400ppm CDO caused 0.73 and 1.25logcfu/g reduction in the numbers of pathogen, respectively, and an additional 2.08 and 2.25logcfu/g reduction, respectively, occurred at day 4. At 400ppm ASC caused a 0.87logcfu/g reduction and an additional 0.86logcfu/g inactivation at day 4. PAA caused ≤0.8logcfu/g reduction in pathogen numbers at ≤400ppm. Among tested antimicrobials, CDO was most effective and had a positive interaction with cold storage where additional E. coli O157:H7 inactivation occurred.

Postharvest intervention technologies for safety enhancement of meat and meat based products; a critical review

Globally, the demand for safe, healthy and nutritious meat and allied products possesses improved taste with extended shelf life is mounting. Microbial safety is among the imperative challenges that prevails in meat products because they provide an ideal medium for the growth of microorganisms particularly pathogenic bacteria. The incidence of these microbes can result quality deterioration of products leading towards food borne diseases when consumed by peoples. Several preservation technologies like chemical and biological interventions are effective to retard or inactivate the growth of micro-organisms most commonly related to food-borne diseases. Despite these, innovative approaches like hydrostatic pressure processing, active packaging, pulse electric field, hurdle approach and use of natural antimicrobials can be deployed to enhance the safety of meat and meat products. The objective of review is to describe the current approaches and developing technologies for enhancing safety of meat and allied meat products.

Reduction of Surrogates for Escherichia coli O157:H7 and Salmonella during the Production of Nonintact Beef Products by Chemical Antimicrobial Interventions

The efficacy of chemical antimicrobials for controlling Escherichia coli O157:H7 and Salmonella during production of marinated nonintact beef products was evaluated using nonpathogenic surrogates. Boneless beef strip loins were inoculated with either approximately 5.8 or 1.9 log CFU/cm(2) (high and low inoculation levels, respectively) of nonpathogenic rifampin-resistant E. coli. Inoculated strip loins were chilled at 2°C for 24 h, vacuum packaged, and aged for 7 to 24 days at 2°C. After aging, strip loins received no treatment (control) or one of five antimicrobial spray treatments: 2.5% L-lactic acid (pH 2.6), 5.0% L-lactic acid (pH 2.4), 1,050 ppm of acidified sodium chlorite (pH 2.8), 205 ppm of peroxyacetic acid (pH 5.2), or tap water (pH 8.6). Mean application temperatures were 53, 26, 20, and 18°C for lactic acid, water, peroxyacetic acid, and acidified sodium chlorite treatments, respectively. Treated and control strip loins were vacuum tumbled in a commercial marinade. Samples were collected throughout the experiment to track the effects of antimicrobial treatment and processing on inoculated surrogates. For high-inoculation strip loins, the 5.0% L-lactic acid treatment was most effective for reducing surrogates on meat surfaces before marination, producing a 2.6-log mean reduction. Peroxyacetic acid treatment resulted in the greatest reduction of surface-located surrogate microorganisms in marinated product. Water treatment resulted in greater internalization of surrogate microorganisms compared with the control, as determined by enumeration of surrogates from cored samples. Producers of nonintact beef products should focus on use of validated antimicrobial sprays that maximize microbial reduction and minimize internalization of surface bacteria into the finished product.

Antimicrobial interventions for O157:H7 and non-O157 Shiga toxin-producing Escherichia coli on beef subprimal and mechanically tenderized steaks

Non-O157 Shiga toxin-producing Escherichia coli (STEC) is an emerging risk for food safety. Although numerous postharvest antimicrobial interventions have been effectively used to control E. coli O157:H7 during beef harvesting, research regarding their effectiveness against non-O157 STEC is scarce. The objectives of this study were (i) to evaluate effects of the spray treatments-ambient water, 5% lactic acid (LA), 200 ppm of hypobromous acid (HA), and 200 ppm of peroxyacetic acid (PA)-on the reduction of O157:H7 or non-O157 STEC (O26, O103, O111, and O145) with high (10(6) log CFU/50 cm(2)) or low (10(2) log CFU/50 cm(2)) levels on beef subprimals after vacuum storage for 14 days and (ii) to evaluate the association of the antimicrobial treatments and cooking (50 or 70°C) on the reduction of the pathogens in blade-tenderized steaks. The treatment effects were only observed (P = 0.012) on samples taken immediately after spray intervention treatment following inoculation with a high level of O157:H7. The LA and PA treatments significantly reduced low-inoculated non-O157 STEC after spray intervention; further, the LA and HA treatments resulted in significant reductions of non-O157 STEC on the low-inoculated samples after storage. Although cooking effectively reduced the detection of pathogens in internal steak samples, internalized E. coli O157:H7 and non-O157 STEC were able to survive in steaks cooked to a medium degree of doneness (70°C). This study indicated that the reduction on surface populations was not sufficient enough to eliminate the pathogen's detection following vacuum storage, mechanical tenderization, and cooking. Nevertheless, the findings of this study emphasize the necessity for a multihurdle approach and further investigations of factors that may influence thermal tolerance of internalized pathogenic STEC.

Shiga toxin-producing Escherichia coli O157, O26 and O111 in cattle faeces and hides in Italy

INTRODUCTION

Ruminants are regarded as the natural reservoir for Shiga toxin-producing Escherichia coli (STEC), especially of serogroup O157.

MATERIALS AND METHODS

During 2011 and 2012, 320 samples (160 faecal samples from the rectum and 160 hide samples from the brisket area) were collected from 160 cattle at slaughter in Northern Italy during warm months (May to October). Cattle were reared in different farms and their age at slaughter ranged between nine months and 15 years, most of them being culled cattle (median age: six years; average age: 4.6 years). Samples were tested by immunomagnetic-separation technique for E coli O157 and O26 and by a screening PCR for stx genes followed by cultural detection of STEC. The virulence genes stx1, stx2, eae, and e-hlyA were detected and among stx2-positive isolates the presence of the stx2a and stx2c variants was investigated.

RESULTS

Twenty-one of 160 cattle (13.1 per cent; 95 per cent CI 8.3 to 19.4 per cent) were found to be faecal carriers of STEC. STEC O157 was found in 10 (6.3 per cent) samples, STEC O26 in six (3.8 per cent) and STEC O111 in one (0.6 per cent). Four isolates (2.5 per cent) were O not determined (OND). Six out of 160 (3.8 per cent; 95 per cent CI 1.4 to 8.0 per cent) hide samples were positive for STEC; four hides (2.5 per cent) were contaminated by STEC O157 and two (1.3 per cent) by STEC O26. In three cattle (1.9 per cent) STEC from both faeces and hides were detected. Among STEC O157, 87.5 per cent of them carried the stx2c gene and 12.5 per cent carried both stx1 and stx2c genes. No O157 isolate harboured stx2a variant. STEC O26 and O111 carried the stx1 gene only. One OND strain carried both the stx2a and stx2c genes.

CONCLUSIONS

This study shows that STEC O157 from cattle can harbour the stx2c variant, which is associated with haemolytic uraemic syndrome in humans, and that cattle hides may be a source of human pathogenic STEC O157 and O26 in the slaughterhouse environment.

Peri- and Postharvest Factors in the Control of Shiga Toxin-Producing Escherichia coli in Beef

Certain Shiga toxin-producing Escherichia coli (STEC) strains are important causes of food-borne disease, with hemorrhagic colitis and, in some cases, hemolytic-uremic syndrome as the clinical manifestations of illness. Six serogroups and one serotype of STEC (O26, O45, O103, O111, O121, O145, and O157:H7) are responsible for the vast majority of cases in the United States. Based on recent data for all food commodities combined, 55.3% and 50.0% of the outbreaks of STEC O157 and non-O157 in the United States, respectively, are attributable to beef as a food source. Consequently, the U.S. Department of Agriculture, Food Safety and Inspection Service declared these organisms as adulterants in raw, nonintact beef. In North America, cattle are a major reservoir of STEC strains, with organisms shed in the feces and contaminated hides of the animals being the main vehicle for spread to carcasses at slaughter. A number of peri- and postharvest interventions targeting STEC have been developed, and significant progress has been made in improving the microbiological quality of beef in the past 20 years as a result. However, continued improvements are needed, and accurate assessment of these interventions, especially for non-O157 STEC, would greatly benefit from improvements in detection methods for these organisms.

Use of lactic acid with electron beam irradiation for control of Escherichia coli O157:H7, non-O157 VTEC E. coli, and Salmonella serovars on fresh and frozen beef

Lactic acid pre-treatment was examined to enhance the antimicrobial action of electron (e-) beam irradiation of beef trim. Meat samples were inoculated with Escherichia coli O157:H7, non-O157 VTEC E. coli or Salmonella cocktails and treated with 5% lactic acid at 55 °C. Samples were packaged aerobically or vacuum-packed, kept at 4 °C and treated with 1 kGy e-beam energy. Frozen samples were treated with 1, 3 or 7 kGy and stored at -20 °C for ≤ 5 d. Lactic acid enhanced the antimicrobial action of 1 kGy e-beam treatment against Salmonella by causing an additional <1.8 log CFU/g reduction. One kGy treatment of refrigerated samples reduced VTEC E. coli viability by 4.5 log CFU/g, and while lactic acid did not improve the reduction, after freezing additive effects were found. After 3 kGy irradiation, Salmonella was reduced by 2 and 4 log CFU/g in the irradiated and lactic acid plus irradiated samples, respectively. Lactic acid pre-treatment was of limited value with 1 kGy treatment for improving control of toxigenic E. coli in fresh beef trim, however, it would be useful with low dose irradiation for controlling both VTEC E. coli and Salmonella in frozen product.

Immersion in antimicrobial solutions reduces Salmonella enterica and Shiga toxin-producing Escherichia coli on beef cheek meat

The objective of this study was to determine the effect of immersing beef cheek meat in antimicrobial solutions on the reduction of O157:H7 Shiga toxin-producing Escherichia coli (STEC), non-O157:H7 STEC, and Salmonella enterica. Beef cheek meat was inoculated with O157:H7 STEC, non-O157:H7 STEC, and S. enterica on both the adipose and muscle surfaces. The inoculated cheek meat was then immersed in one of seven antimicrobial solutions for 1, 2.5, or 5 min: (i) 1% Aftec 3000 (AFTEC), (ii) 2.5% Beefxide (BX), (iii) 300 ppm of hypobromous acid (HOBR), (iv) 2.5% lactic acid (LA2.5), (v) 5% lactic acid (LA5), (vi) 0.5% levulinic acid and 0.05% sodium dodecyl sulfate (LEV-SDS), or (vii) 220 ppm of peroxyacetic acid (POA). Inoculated cheek meat was also immersed in 80 °C tap water (HW) for 10 s. In general, increasing immersion duration in antimicrobial solutions did not significantly (P ≥ 0.05) increase effectiveness. Immersion in HW for 10 s was the most effective intervention, reducing STEC and S. enterica by 2.2 to 2.3 log CFU/cm2 on the adipose surface and by 1.7 to 1.8 log CFU/cm2 on the muscle surface. Immersion for 1 min in AFTEC, BX, LA2.5, LA5, or POA was also effective as an intervention, reducing STEC and S. enterica by 0.8 to 2.0 log CFU/cm2 on the adipose surface and by 0.6 to 1.4 log CFU/cm2 on the muscle surface. Immersion for 1 min in HOBR or LEV-SDS was not an effective intervention because STEC and S. enterica reductions ranged from 0.1 to 0.4 log CFU/cm2, which were not significantly different (P ≥ 0.05) from the reductions obtained when cheek meat was immersed in room temperature tap water. We conclude that immersion of cheek meat in HW for 10 s and immersion for 1 min in AFTEC, BX, LA2.5, LA5, or POA effectively reduced levels of STEC and S. enterica.

A review of factors that affect transmission and survival of verocytotoxigenic Escherichia coli in the European farm to fork beef chain

Verocytotoxigenic Escherichia coli (VTEC) are a significant foodborne public health hazard in Europe, where most human infections are associated with six serogroups (O157, O26, O103, O145, O111 and O104). With the exception of O104, these serogroups are associated with bovine animals and beef products. This paper reviews our current knowledge of VTEC in the beef chain focusing on transmission and the factors which impact on survival from the farm through transport, lairage, slaughter, dressing, processing and distribution, in the context of the European beef industry. It provides new information on beef farm and animal hide prevalence, distribution and virulence factors as well as pre-chilled carcass and ground beef prevalence, generated by the recently completed EU Framework research project, ProSafeBeef. In the concluding section, emerging issues and data gaps are addressed with a view to increasing our understanding of this pathogen and developing new thinking on detection and control.

Use of sodium lauroyl sarcosinate (sarkosyl) in viable real-time PCR for enumeration of Escherichia coli

The cell membranes of inactivated Escherichia coli are not always permeable to propidium monoazide (PMA). This limits the use of PMA real-time PCR (PMA-qPCR) for quantification of DNA from only viable cells for enumeration of E. coli. The aim of this study was to develop PMA-qPCR procedures for E. coli with improved selectivity for viable cells. E. coli inactivated by incubation at 52°C were treated with 12 detergents before PMA treatment, and DNA was quantified by real-time PCR. Treatment with each of the 12 detergents and PMA increased the cycle threshold (Ct) values for heat inactivated E. coli suspensions. The greatest increase, of 10.68 Ct was obtained with sarkosyl. Treatment with sodium deoxycholate (NaDC) increased the Ct value by 8.99 Ct. Treatment with sarkosyl or NaDC of 16 heat treated 5-strain cocktails of verotoxigenic E. coli (VTEC) increased the mean Ct values by 8.15 or 6.82 Ct, respectively. Those mean values were significantly (p<0.05) different. When used to enumerate viable E. coli in suspensions treated with lactic acid or in mixtures of viable E. coli and E. coli inactivated by peroxyacetic acid, the slopes relating the Ct values from sarkosyl treated samples to the numbers of viable E. coli were 2.24 and 2.47, respectively, with regression coefficient values ≥0.85. The findings show that sarkosyl was more effective than NaDC for dissipation of PMA-barrier properties of membranes of inactivated E. coli cells. Viable E. coli in mixtures of viable E. coli and E. coli inactivated by heat, lactic acid or peroxyacetic acid could be reliably enumerated by sarkosyl PMA-qPCR.

Use of a bacteriophage cocktail to control Salmonella in food and the food industry

The use of lytic bacteriophages for the biocontrol of food-borne pathogens in food and in the food industry is gaining increasing acceptance. In this study, the effectiveness of a bacteriophage cocktail composed of three different lytic bacteriophages (UAB_Phi 20, UAB_Phi78, and UAB_Phi87) was determined in four different food matrices (pig skin, chicken breasts, fresh eggs, and packaged lettuce) experimentally contaminated with Salmonella enterica serovar Typhimurium and S. enterica serovar Enteritidis. A significant bacterial reduction (>4 and 2 log/cm(2) for S. Typhimurium and S. Enteritidis, respectively; p≤0.005) was obtained in pig skin sprayed with the bacteriophage cocktail and then incubated at 33 °C for 6h. Significant decreases in the concentration of S. Typhimurium and S. Enteritidis were also measured in chicken breasts dipped for 5 min in a solution containing the bacteriophage cocktail and then refrigerated at 4 °C for 7 days (2.2 and 0.9 log10 cfu/g, respectively; p≤0.0001) as well as in lettuce similarly treated for 60 min at room temperature (3.9 and 2.2 log10 cfu/g, respectively; p≤0.005). However, only a minor reduction of the bacterial concentration (0.9 log10 cfu/cm(2) of S. Enteritidis and S. Typhimurium; p≤0.005) was achieved in fresh eggs sprayed with the bacteriophage cocktail and then incubated at 25 °C for 2 h. These results show the potential effectiveness of this bacteriophage cocktail as a biocontrol agent of Salmonella in several food matrices under conditions similar to those used in their production.

Sensitivity of Shiga toxin-producing Escherichia coli, multidrug-resistant Salmonella, and antibiotic-susceptible Salmonella to lactic acid on inoculated beef trimmings

Studies were performed to determine whether lactic acid treatments used to reduce Escherichia coli O157:H7 on beef trimmings are also effective in controlling non-O157 Shiga toxin-producing E. coli (nSTEC), and multidrug-resistant and antibiotic-susceptible Salmonella. Beef trimming pieces (10 by 5 by 1 cm) were inoculated (3 log CFU/cm(2)) separately with four-strain mixtures of rifampin-resistant E. coli O157:H7, O26, O45, O103, O111, O121, and O145. Similarly, in a second study, trimmings were separately inoculated with rifampin-resistant E. coli O157:H7, and antibiotic-susceptible or multidrug-resistant (MDR and/or MDR-AmpC) Salmonella Newport and Salmonella Typhimurium. Inoculated trimmings were left untreated (control) or were immersed for 30 s in 5% lactic acid solutions (25 or 55°C). No differences (P ≥ 0.05) were obtained among surviving counts of E. coli O157:H7 and those of the tested nSTEC serogroups on lactic acid-treated (25 or 55°C) samples. Counts (3.1 to 3.3 log CFU/cm(2)) of E. coli O157:H7 and nSTEC were reduced (P < 0.05) by 0.5 to 0.9 (25°C lactic acid) and 1.0 to 1.4 (55°C lactic acid) log CFU/cm(2). Surviving counts of Salmonella on treated trimmings were not influenced by serotype or antibiotic resistance phenotype and were similar (P ≥ 0.05) or lower (P < 0.05) than surviving counts of E. coli O157:H7. Counts (3.0 to 3.3 log CFU/cm(2)) were reduced (P < 0.05) by 0.5 to 0.8 (E. coli O157:H7) and 1.3 to 1.5 (Salmonella) log CFU/cm(2) after treatment of samples with 25°C lactic acid. Corresponding reductions following treatment with lactic acid at 55°C were 1.2 to 1.5 (E. coli O157:H7) and 1.6 to 1.9 (Salmonella) log CFU/cm(2). Overall, the results indicated that lactic acid treatments used against E. coli O157:H7 on beef trimmings should be similarly or more effective against the six nSTEC serogroups and against multidrug-resistant and antibiotic-susceptible Salmonella Newport and Salmonella Typhimurium.

Effects of lactic acid on the growth characteristics of Listeria monocytogenes on cooked ham surfaces

The surfaces of ready-to-eat meats are susceptible to postprocessing contamination by Listeria monocytogenes. This study examined and modeled the growth characteristics of L. monocytogenes on cooked ham treated with lactic acid solutions (LA). Cooked ham was inoculated with L. monocytogenes (ca. 10(3) CFU/g), immersed in 0, 0.5, 0.75, 1.0, 1.25, 1.5, and 2.0% LA for 30 min, vacuum packaged, and stored at 4, 8, 12, and 16°C. LA immersion resulted in <0.7 log CFU/g immediate reduction of L. monocytogenes on ham surfaces, indicating the immersion alone was not sufficient for reducing L. monocytogenes. During storage, no growth of L. monocytogenes occurred on ham treated with 1.5% LA at 4 and 8°C and with 2% LA at all storage temperatures. LA treatments extended the lag-phase duration (LPD) of L. monocytogenes and reduced the growth rate (GR) from 0.21 log CFU/day in untreated ham to 0.13 to 0.06 log CFU/day on ham treated with 0.5 to 1.25% LA at 4°C, whereas the GR was reduced from 0.57 log CFU/day to 0.40 to 0.12 log CFU/day at 8°C. A significant extension of the LPD and reduction of the GR of L. monocytogenes occurred on ham treated with >1.25% LA. The LPD and GR as a function of LA concentration and storage temperature can be satisfactorily described by a polynomial or expanded square-root model. Results from this study indicate that immersion treatments with >1.5% LA for 30 min may be used to control the growth of L. monocytogenes on cooked meat, and the models would be useful for selecting LA immersion treatments for meat products to achieve desired product safety.

Evaluation of commonly used antimicrobial interventions for fresh beef inoculated with Shiga toxin-producing Escherichia coli serotypes O26, O45, O103, O111, O121, O145, and O157:H7

Although numerous antimicrobial interventions targeting Escherichia coli O157:H7 have been developed and implemented to decontaminate meat and meat products during the harvesting process, the information on efficacy of these interventions against the so-called Big Six non-O157 Shiga toxin-producing E. coli (STEC) strains is limited. Prerigor beef flanks (160) were inoculated to determine if antimicrobial interventions currently used by the meat industry have a similar effect in reducing non-O157 STEC serogroups O26, O45, O103, O111, O121, and O145 compared with E. coli O157:H7. A high (10(4) CFU/cm(2)) or a low (10(1) CFU/cm(2)) inoculation of two cocktail mixtures was applied to surfaces of fresh beef. Cocktail mixture 1 was composed of O26, O103, O111, O145, and O157, while cocktail mixture 2 was composed of O45, O121, and O157. The inoculated fresh beef flanks were subjected to spray treatments by the following four antimicrobial compounds: acidified sodium chlorite, peroxyacetic acid, lactic acid, and hot water. High-level inoculation samples were enumerated for the remaining bacteria populations after each treatment and compared with the untreated controls, while low-level inoculation samples were chilled for 48 h at 4°C before enrichment, immunomagnetic separation, and isolation. Spray treatments with hot water were the most effective, resulting in mean pathogen reductions of 3.2 to 4.2 log CFU/cm(2), followed by lactic acid. Hot water and lactic acid also were the most effective interventions with the low-level inoculation on surfaces of fresh beef flanks after chilling. Peroxyacetic acid had an intermediate effect, while acidified sodium chlorite was the least effective in reducing STEC levels immediately after treatment. Results indicate that the reduction of non-O157 STEC by antimicrobial interventions on fresh beef surfaces were at least as great as for E. coli O157:H7. However, the recovery of these low inoculation levels of pathogens indicated that there is no single intervention to eliminate them.