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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Meat Safety & Quality Research » Research » Research Project #430703

Research Project: Mitigation Approaches for Foodborne Pathogens in Cattle and Swine for Use During Production and Processing

Location: Meat Safety & Quality Research

2016 Annual Report


1a. Objectives (from AD-416):
Objective 1: Develop and validate novel pre- and post-harvest intervention strategies to reduce or eliminate foodborne pathogen colonization and persistence in the animal and on carcasses and meat products. Sub-objective 1.A: Identify effective control measures to reduce pathogens and in the pre-harvest environment. Sub-objective 1.B: Identify and/or improve efficacious non-thermal post-harvest interventions to reduce contamination of processing plant surfaces, hides, carcasses, and meat products. Sub-objective 1.C: Determine if current processing interventions are equally effective on AMR bacteria and foodborne pathogens. Objective 2: Develop improved sampling, detection, and tracking technologies to identify points, including biofilms, where pathogens persist and contaminate in the production of red meat. Sub-objective 2.A: Characterization of bacterial and environmental components contributing to high event periods (HEP) of E. coli O157:H7 contamination at beef processing plants. Sub-objective 2.B: Identify improved sampling and detections technologies for foodborne pathogens associated with red meat. Sub-objective 2.C: Develop and evaluate indicator organisms as surrogates for tracking pathogens through beef processing. Objective 3: Identify environmental and management practices that influence antimicrobial resistance, colonization of lymph nodes, and colonization rates of cattle, veal, and swine. Sub-objective 3.A: Determine effects of season and production system on occurrence of antimicrobial resistance and foodborne pathogens associated with food animal production. Sub-objective 3.B: Identify environmental and management practices that influence Salmonella in lymph nodes. Sub-objective 3.C: Determine the prevalence of STEC and AMR in veal production systems and identify factors contributing to colonization.


1b. Approach (from AD-416):
Cattle and swine can serve as reservoirs of foodborne pathogens that can spread through the environment or to meat during harvest. Further, pharmacologic antimicrobial use in meat animal production is a concern due to the perceived possibility of emergence and transmission of antimicrobial resistant (AMR) bacteria to the environment and food supply. Research to develop ways to reduce the levels of foodborne pathogens such as Shiga-toxin producing Escherichia coli (STEC) and Salmonella on farms and in foods is important, as is understanding and reducing the risk posed to food safety by AMR bacteria present in the meat production system. To this end, the effects of animal vaccines and direct fed microbial feed additives will be investigated to reduce or eliminate foodborne pathogens in the pre-harvest environment. During the harvest process, chlorine dioxide gas, cold atmospheric plasma, and a unique nano-technology sprayer will be assessed to reduce contamination. Novel methods to detect and track pathogens will be designed and tested including examining processing plants for biofilms and determining their roles during times of widespread pathogen contamination. Environmental and animal management practices that influence antimicrobial resistance and colonization of meat animals by pathogens will be studied, with the goal of identifying management practices that influence Salmonella in beef carcass lymph nodes and the prevalence of STEC in veal production. Successful completion of the project objectives will increase the ability of producers and processors to monitor production and use improved interventions to control contamination and product loss, and clarify the risk of antimicrobial resistance in meat production, while providing meat consumers a decreased risk of foodborne illness.


3. Progress Report:
This is the annual report for the project titled Mitigation Approaches for Foodborne Pathogens in Cattle and Swine for Use During Production and Processing (3040-42000-018-00D) that has replaced the project titled Pathogen Mitigation In Livestock And Red Meat Production (3040-42000-014-00D) progress has been made on all three objectives. Under Objective 1: Develop and validate novel pre- and post-harvest intervention strategies to reduce or eliminate foodborne pathogen colonization and persistence in the animal and on carcasses and meat products, two studies have been completed. First, current antimicrobials such as lactic acid, peracetic acid, cetylpyridinium chloride, and sodium hydroxide have been used in the meat industry to reduce pathogenic bacteria. However, effectiveness of these antimicrobials on non-antimicrobial resistance (non-AMR) and antimicrobial resistance (AMR) bacteria has not been determined. A study was performed using beef purge containing either non-AMR or AMR Salmonella and subjected to the antimicrobials. Our findings indicate that lactic acid, Peracetic acid, and cetylpyridinium chloride are equally effective in reducing non-AMR and AMR Salmonella. Second, there has been increased interest in the application of antimicrobial spray treatments to beef trimmings prior to grinding and to beef subprimals before packaging for the reduction of microbial contamination during processing. However, the Food safety and Inspection Service (FSIS) only allows for a maximum of 0.5% of liquid gained after spray application of antimicrobials. A study was performed in which beef trimmings and subprimals were surface inoculated with a ten-strain cocktail mixture of E. coli O157:H7 and Salmonella and subjected to water and four different concentrations of peracetic acid (130, 150, 200, and 400 ppm). Results indicated that all concentrations of peracetic acid significantly reduced E. coli O157:H7 and Salmonella on beef trimmings and subprimals compared to water and can be used during beef processing to improve the safety of beef trimmings and subprimals when weight gain is limited to <= 0.5% to meet regulatory requirements. Under Objective 2: Develop improved sampling, detection, and tracking technologies to identify points, including biofilms, where pathogens persist and contaminate in the production of red meat, we have been making significant progress towards determining specific bacterial and environmental components that might contribute to “High Event Period” (HEP) trim contamination by E. coli O157:H7 at beef processing plants. We have phenotypically and genetically characterized and compared the E. coli O157:H7 HEP strains and control panel strains for their biofilm forming ability and sanitizer resistance. Our results showed that compared to the control panel strains, E. coli O157:H7 strains isolated from HEP events had stronger biofilm forming ability on materials commonly used in the meat industry as well as lower susceptibility to common sanitizers. The HEP strains also harbored a higher copy number of the pO157 plasmid, which was positively correlated to the stronger potency of “mature” biofilm formation and higher survival /recovery growth capability after sanitization. Taken together, these results suggest that the pO157 plasmid might play important roles in the phenotypes of biofilm formation and sanitizer resistance by certain E. coli O157:H7 strains that pose higher potential of causing HEP contamination in the meat plants. This study may help answer the important question for the industry if environmental colonization of certain E. coli O157:H7 strains contribute to HEP contamination at the processing plants. Under Objective 3: Identify environmental and management practices that influence antimicrobial resistance, colonization of lymph nodes, and colonization rates of cattle, veal and swine, we investigated the relationship between antibiotic usage in livestock and development of antimicrobial resistance in associated bacterial populations. Breeding beef cows (hereafter referred to as beef cows), typically pasture raised, make up one third of the cattle inventory in the United States, but there is a paucity of information regarding antimicrobial resistance in beef cows. We compared the occurrences of resistance to specific classes of antimicrobials in bacteria from the fecal samples of beef cows more than 8 years old for which complete antimicrobial treatment records were available. Approximately half of the cows sampled for this study were treated with antimicrobials for the treatment of disease, while the other half did not receive any antimicrobial treatments over their lifetime. The prevalences of antimicrobial resistant bacteria were not significantly (P > 0.05) associated with prior history of antimicrobial treatments or duration of time between last antimicrobial treatment and sampling. In conclusion, occurrences of antimicrobial resistance in comingled beef cows were not associated with antimicrobial use indicating that other factors more strongly influenced the observed levels of antimicrobial-resistant bacteria in feces of beef cows. We conducted a study to follow cattle that had experienced a salmonellosis outbreak from the feedlot through harvest and determine if salmonellosis, resolved through antimicrobial therapy, results in persistent colonization of bovine peripheral lymph nodes. Based on the results of the study it is clear that salmonellosis outbreaks in cattle do not result in long-term carriage of the outbreak strain. It was unknown prior to this study if bovine peripheral lymph nodes from cattle that had salmonellosis infections would be persistently infected leading to increased food safety risk at harvest. The findings of this study indicate that cattle that are treated for salmonellosis provide no increased risk of lymph node colonization by Salmonella at harvest. We have begun to determine the effects of season and production system (conventional and raised without antimicrobials) on occurrence of antimicrobial resistance and foodborne pathogens associated with food animal production. To date, 720 fecal samples have been collected. Half from cattle produced conventionally (with antimicrobials) and half from cattle raised without antimicrobials. Antimicrobial resistant bacteria have been cultured, and genomic DNA has been isolated from these samples.


4. Accomplishments
1. Antimicrobial-resistant bacterial populations and antimicrobial resistance genes obtained from environments impacted by livestock and municipal waste. The impact of potential antimicrobial resistant bacteria in livestock waste runoff has been a growing topic of public concern. ARS scientists at Clay Center, Nebraska, compared the populations of antimicrobial-resistant bacteria and the presence of antimicrobial resistance genes within samples of livestock and municipal waste streams discharged from municipal wastewater treatment facilities, cattle feedlot runoff catchment ponds, swine waste lagoons and environments considered low impact (a municipal lake and a prairie). The results showed prevalences and concentrations of antimicrobial-resistant bacteria were similar among the livestock and municipal sample sources, but there were differences among the antimicrobial resistance genes found in agricultural, environmental, and municipal samples, with municipal samples harboring the highest number of antimicrobial resistance genes. It was concluded that antimicrobial resistance is a very widespread phenomenon where antimicrobial resistance can be found in cattle, swine, and human waste streams, but the higher diversity of antimicrobial resistance can be found in human waste streams.