S1033: Control of Food-Borne Pathogens in Pre- and Post-Harvest Environments
Statement of Issues and Justification
The Centers for Disease Control and Prevention (CDC, 1999) reported new, more accurate estimates of foodborne illnesses that occur annually. An estimated 76 million cases of foodborne illness, 325,000 hospitalizations, and 5,000 deaths occur each year from food-borne microorganisms (Mead et al., 1999). The food safety surveillance system, FoodNet, indicates that more cases of food-borne illness occurred, but fewer deaths were caused by foodborne disease agents than previously reported. Campylobacter spp. was responsible for the most cases of foodborne illness. Salmonella (nontyphoidal) caused the most deaths; Listeria monocytogenes also causing a significant number of deaths. In summary, the report indicates that foodborne pathogens have a significant impact on human health and the food industry in the United States.In addition to human suffering, foodborne illnesses also have a substantial economic impact in the United States. The annual cost of foodborne illness in the U.S. is estimated at $5-$6 billion for loss of productivity and medical expenses (Marks and Roberts, 1993). The most costly food-borne illnesses are caused by Toxoplasma gondii, Salmonella spp., Campylobacter spp., and enterohemorrhagic Escherichia coli.
New methods to prevent, reduce or eliminate foodborne disease agents at all points of the food chain, from farm to fork , are needed to improve the safety of the food supply to prevent illnesses and deaths and to prevent economic losses to the food industry.
Produce: An increasing number of gastrointestinal disease outbreaks have been linked to the consumption of fresh fruits and vegetables. The increase in the number of outbreaks caused by produce appears to be related to the increased demand for fresh fruits and vegetables. Between 1990 and 2001, contaminated fresh produce caused 148 outbreaks that account for approximately 9% of all food-borne outbreaks (Smith-DeWaal et al, 2002). Two of the most virulent foodborne pathogens, Salmonella and pathogenic Escherichia coli, have been responsible for many outbreaks associated with fresh fruits and vegetables. Fresh fruits and vegetables are considered high-risk foods because they are minimally processed and are susceptible to contamination by manure or soil at the farm.
The FDA in collaboration with the USDA and the Centers for Disease Control CDC issued a series of guidelines referred as Good Agricultural Practices (GAPs) to reduce the risk of foodborne diseases from fresh fruits and vegetables (FDA/USDA/CDC, 2003). Even with implementation and strict adherence to the GAPs guidelines, a potential still exists for contamination of fresh fruits, vegetables and nutmeats. To further reduce or prevent the potential for finished produce and nutmeat contamination, decontamination methods must be employed. Traditional decontamination treatments (thermal processing, chlorination and irradiation) adversely affect the desirable characteristics of the majority of fresh fruits, vegetables and nutmeats. Therefore, alternative methods or different parameters for existing methods must be developed for the decontamination of produce and nutmeats.
Meat and Poultry: Foodborne salmonellosis in the U.S. causes approximately 1.3 million illnesses, 15,600 hospitalizations and 550 deaths annually and is most often associated with meat and egg products. Undercooked and/or improperly chilled meat and eggs have been identified as one of the most frequent causes of foodborne illness in the United States. Heating and chilling of meat, eggs and meat products are critical processes for controlling growth of foodborne pathogens. Chilling of meat animal carcasses, fresh eggs and freshly-cooked, ready-to-eat meat products using air chilling is a complex process that is widely used in industry. Specification and evaluation of rate of temperature decline are essential in controlling the microbiological hazards such as Escherichia coli O157:H7, Clostridium perfringens and Salmonella spp. to insure food safety.
Requirements for processing of meat and poultry products are published in Title 9 of the Code of Federal Regulations and include performance standards to control pathogens. The lethality performance standard is based on destruction of the pathogenic microorganism Salmonella (USDA-FSIS, 2002). The lethality standard states that manufacturers must use a combination of thermal and non-thermal processes sufficient to achieve a 6.5-log10 reduction in Salmonella in ready-to-eat, cooked beef, roasted beef, cooked corned beef (9 CFR 318.17) and a 7-log10 reduction in ready-to-eat poultry products (9 CFR 381.150). Alternatively, processors may follow USDA compliance or safe harbor guidelines. Safe harbor guidelines listing specific processing times and temperatures for beef patties are in effect (9 CFR 318.23). If a processor elects to use their own process, they must provide evidence that the process meets the lethality performance standard. More research is needed to understand and predict microbial lethality during thermal processing.
The stabilization performance standard is designed to prevent growth of pathogens in cooked product during chilling and cold storage. The stabilization performance standards require no multiplication of toxigenic microorganisms, such as Clostridium botulinum, and no more than a 1 log10 multiplication of C. perfringens within the product after cooking for poultry (9 CFR 381.150), roast beef (9 CFR 318.17) and beef patties (9 CFR 318.23). Specification and evaluation of rate of temperature decline within a product are essential in controlling microbiological hazards due to E. coli O157:H7, C. perfringens and Salmonella spp. to insure food safety.
Bovine pre-harvest food safety: Over the past decade, Escherichia coli O157:H7 has emerged as a significant public health concern. Infection with this pathogen in humans is associated with a range of clinical syndromes, including mild to severe bloody diarrhea and hemolytic uremic syndrome. E. coli O157:H7 is considered a transient member of the normal flora of cattle and is only rarely associated with clinical disease in cattle. However, cattle are important sources of E. coli O157:H7, with beef and beef products being implicated in many food borne disease outbreaks of E. coli O157:H7 in humans. E. coli O157:H7-contaminated meat linked to human outbreaks of disease can have devastating effects on the industry because of product recalls and reduced consumer confidence. Thus, from both a humanitarian and an economic perspective, E. coli O157:H7 removal from the food supply is both a state and a national priority.
Control of E. coli O157:H7, to be effective, will require the implementation of intervention strategies throughout the food chain continuum, from farm to table. Sanitation efforts after slaughter have been demonstrated to reduce contamination of carcasses with E. coli O157:H7. However, pre-harvest intervention strategies may reduce E. coli O157:H7 levels prior to entry in the food processing chain. At the farm level, intervention measures that have been investigated or are currently under investigation include competitive exclusion, general sanitation strategies, dietary component modifications, and pre-slaughter feeding strategies. An area of on-farm E. coli O157:H7 control that has not been investigated is the role of an immunosuppressive pathogen such as bovine viral diarrhea virus (BVDV) on fecal E. coli O157:H7 shedding. BVDV is widely distributed among cattle, and identifying a potential on-farm risk factor for E. coli O157:H7 will assist the beef and dairy industry by identifying critical control strategies to minimize the threat of human food borne illnesses associated with E. coli O157:H7, as well as ensuring consumer confidence through the provision of wholesome food.
Seafood: A major food industry concern is the ability of Listeria monocytogenes to grow at refrigerator temperatures, resist various environmental conditions and thus survive longer under adverse conditions. L. monocytogenes has been found in the environments of crawfish and smoked fish processing plants. These environments include drains, floors, condensate lines, crates, door handles, and conveyor belts (Destro et al., 1996; Thimothe et al., 2002) and can serve as a source for L. monocytogenes contamination of raw seafood and smoked fish and post-processed seafood. Rinse treatments and other measures that reduce L. monocytogenes on smoked fish and seafood would be valuable.
The CDC estimates that noroviruses alone cause 9.2 million cases of acute foodborne gastroenteritis a year, and at least 50% of all foodborne gastroenteritis outbreaks can be attributed to noroviruses (Shabin, 2004; CDC, 2003; Schaub and Oshiro. 2000). Generally, foods that are minimally processed or encounter a high degree of handling are susceptible to virus contamination. With a concurrent increase in the use and consumer interest in innovative nonthermal process technologies (such as high hydrostatic pressure processing or HPP) to improve the sensory quality of foods, there is a need to understand and predict the sensitivity of infective viruses in foods to these newly developed technologies to ensure product safety (Calci et al., 2005; Hoover et al., 1989.
Antimicrobial drug resistance: Antibiotics and other growth-promoting antimicrobials have been used as feed additives for over 50 years. The economic benefits to the animal producer include improved growth rate and feed conversion, reduced mortality, improved health, and greater resistance to disease challenge (Jukes, 1972; Guest, 1976; Hays, 1978). A recent review of the literature indicated that in 12,153 feeding studies, dietary antimicrobial growth promotants successfully increased growth performance 72% of the time (Rosen, 1996).
Today, more than 50% of all antibiotics produced are used in animal feeds. Despite the success of this practice, the inclusion of antibiotics in animal feeds to enhance growth is banned in many countries. The use of antibiotics for growth promotion requires long-term subtherapeutic addition of the antibiotic in the feed. Unfortunately, these practices may increase the prevalence of antibiotic-resistant bacteria in the animal (Fuller et. al. 1960; Langlois et. al., 1978 a, b; Morehead and Dawson, 1992). Some have proposed that this increase in antibiotic-resistant bacteria in the animal may result in an increase in antibiotic-resistant bacteria in the food supply, which could ultimately result in human illnesses (Guest, 1976; Novick, 1981). Antibiotic-resistant bacteria pose a significant human health risk if they are pathogens, or if they transfer the resistance to pathogens (Corpet, 1988). Many consumer groups and researchers in the United States support the elimination of subtherapeutic doses of antibiotics in animal feeds in an attempt to reduce or eliminate antibiotic resistant bacterial populations in livestock.
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