Still Afraid of the Big Bad Bugs?
By Julie Larson Bricher
In April 2004, the Centers for Disease Control and Prevention (CDC) reported a encouraging trend: Some of the most common diseases associated with foodborne pathogens, parasites and other bacteria are on the decline or holding steady. In the U.S., E. coli O157:H7 infections decreased a dramatic 36% in just one year, posting an overall decline of 42% since FoodNet surveillance began in 1996. Campylobacter, Salmonella, Cryptosporidium and Yersinia infections also had considerable declines in the eight-year surveillance period, at 28%, 17%, 51% and 49%, respectively. While Shigella and Listeria infections did not post significant decreases in estimated incidence rates, they fortunately did not increase either.
Even better, CDC credited the food industry’s efforts in implementing food safety science-based programs and systems, along with federal food safety agencies’ policies and guidances, with these reductions. But does this mean that the food and beverage industry can let down its guard?
The short answer is no. There are plenty of reasons that we must remain vigilant in identifying what additional kinds of efforts can be undertaken to prevent and control foodborne illness-causing pathogens. Continuing to utilize technologies in detection and process control and staying abreast of new developments in identifying and reducing the incidence of microbial contamination from the food processing environment are key to furthering the nation’s—and the processing industry’s—food safety agenda. The oft-quoted figure from Mead’s 1999 estimate of food-related illness and death in the U.S. state that foodborne diseases cause approximately 76 million illnesses, 325,000 hospitalizations and 5,000 deaths in the U.S. each year, with known pathogens accounting for an estimated 14 million illnesses, 60,000 hospitalizations and 1,800 deaths. But that does not account for unreported illnesses and fatalities, which likely pushes these estimates even higher. In addition, the National Center for Health Statistics estimates a higher number of deaths per year from foodborne illness at 9,100. And, according to a U.S. Food and Drug Administration (FDA) estimate, 2-3% of pathogen-related foodborne illness may lead to secondary long-term illnesses such as meningitis from Listeria infection or kidney failure in young children as a result of E. coli O157:H7 infection. The battle is far from over.
A close look at the 2004 FoodNet preliminary surveillance data shows that, in addition to the success of industry and government efforts to reduce the incidence of foodborne pathogens that cause illness, some microbes continue to pose significant problems. After a four-year decline, Listeria infections did not continue to decrease in 2003, despite concerted efforts on the part of industry to institute focused strategies to combat the ubiquitous bug. The data also shows that the incidence of Vibrio infections actually increased 116% from 1996-2003, and that although the incidence of Salmonella declined, it remains above the Healthy People 2010 national health objectives. Among the five most common Salmonella serotypes, only S. Typhimurium demonstrated a sustained decline in incidence, and the incidence rate of Salmonella Enteritidis infections has not changed significantly since 1996.
The available estimates of costs of foodborne illness associated with the microbial contamination of foods, both economically and in terms of public health, also are sobering:
• The U.S. Department of Agriculture’s Economic Research Service (USDA ERS) estimated in 2000 the medical costs, costs of premature deaths and losses in productivity resulting from five major foodborne pathogens—Campylobacter, Salmonella (nontyphoidal), E. coli O157, E. coli non-O157 STEC, and Listeria monocytogenes—at $6.9 billion.
• Of the seven pathogens analyzed by USDA, Salmonella and Toxoplasma gondii are the two most costly, largely because of the high number of Salmonella cases annually and because of the severity of the chronic illness caused by Toxoplasma gondii. Salmonellosis infections in 1993 were responsible for an estimated $600 million to $3.5 billion in medical costs and lost productivity. At the same time, toxoplasmosis costs an estimated $2.7 billion annually.
• In 2003, ERS updated its estimate of the annual economic costs due to foodborne Salmonella infections, the second most frequently reported cause of foodborne illness in the U.S., causing 1.4 million annual illnesses and resulting in an estimated 16,000 hospitalizations and 600 deaths each year, to $2.9 billion.
These figures are a bit fear-provoking, but of the estimated 250 foodborne pathogens identified by CDC, the reality is that a specific few are identified as the most common sources of concern for the food supply chain, from farm to processing facility to food handling at foodservice, retail or home. Although the epidemiology of foodborne disease continues to change as new pathogens and vehicles of contamination emerge, making it difficult to address all pathogens in all foods all of the time, the good news is that the implementation of integrated food safety strategies, good detection methods and appropriate control mechanisms by food manufacturers is having a significant impact on the reduction of the hazards posed by microbial contamination across all categories.
This guide to online resources highlights some of the recent and promising research and scientific advances in microbial prevention, detection and process control technologies that the food industry is using to banish the big, bad bugs from production lines. Listed alphabetically by the common pathogens of interest to food safety professionals, resources referenced under one pathogen may also contain useful information pertaining to the detection and control of others.
According to CDC, Campylobacter is the most common bacterial cause of diarrhea in the U.S., resulting in nearly 2 million illnesses each year. The most significant common food vehicles for Campylobacter jejuni or coli are poultry and swine, and the pathogen also has been associated with milk, mushrooms, clams, hamburger, water, cheese, pork, shellfish, eggs and cake icing.
Updated in July, this report page details the National Advisory Committee on Microbiological Criteria For Foods’ (NACMCF) Campylobacter Subcommittee’s latest charge pertaining to advances and use of laboratory methods for identification and quantification of the pathogen.
“Campylobacter: Unmasking the Secret Genes of a Food-Poisoning Culprit” is a timely article on current USDA ARS research, published in the October 2004 issue of Agricultural Research magazine. Discusses the ARS Produce Safety and Microbiology Research Unit’s genome sequencing efforts aimed at furthering the development of microarray, or gene chip, analyses that may lead to better prevention and control methods.
The 2003 Annual Report on the ARS Poultry Microbiological Safety Research Unit research project, “Campylobacter Spp. Epidemiology, Methods Development and Interventions in Poultry,” provides a solid overview of the data being gathered from poultry production operations to identify the sources of Campylobacter contamination; to create directed interven-tions aimed at reducing levels of Campylobacter; to provide predictive models (quantitative risk assessment); and to develop methods for the rapid detection of Campylobacter in complex matrices.
Escherichia coli O157:H7
Since 1982, E. coli O157:H7 has emerged as an important cause of foodborne illness. CDC estimates this pathogen causes approximately 73,000 illnesses and 61 deaths annually. The major common food vehicle is beef, primarily ground beef, and the pathogen has been associated with other food sources, including poultry, apple cider, raw milk, vegetables, cantaloupe, hot dogs, mayonnaise and salad bar items.
This site offers workshop materials provided by FSIS through its 2004 small and very small meat plant outreach efforts, updating information in three recently revised and released FSIS directives dealing with E. coli O157:H7. Materials include revised guidelines and sampling diagrams for FSIS Directive 10,010.1, Revision 1, Microbiological Testing Program and Other Verification Activities for Escherichia coli O157:H7 in Raw Ground Beef Products and Raw Ground Beef Components and Beef Patty Components, as well as zero tolerance and verification of procedures for controlling fecal material, ingesta and milk in slaughter operations.
Prepared by a task force of 13 scientists and downloadable for a nominal fee, “Intervention Strategies for the Microbiological Safety of Foods of Animal Origin,” is an issue paper that provides a timely consideration of critical issues: microbiological safety of foods of animal origin during production; food processing strategies for manufactured foods of animal origin, both ready-to-cook and ready-to-eat; food safety initiatives in retailing; consumer interventions to enhance food safety; challenges to applying food safety controls uniformly across all sectors of the foodservice industry; and recommendations for development and application of new intervention strategies to decrease human illnesses attributed to foods derived from animals.
“Targeting E. coli Infections at Their Source,” published in the August 2004 issue of Agricultural Research, details the work of government scientists working to develop and test an oral vaccine that eliminates E. coli O157:H7 bacteria from cattle.
Extensive links to completed research studies on E. coli O157:H7 and other pathogens affecting the beef industry. Much of the research focuses on innovations in pathogen reduction technologies and interventions, pre- to post-processing.
According to CDC, the rate of listeriosis fell by 35% from 1996-2002, but has since reached a plateau. Each year, L. monocytogenes causes an estimated 2,493 cases of listeriosis and 499 deaths. In 2000, the CDC reported that of all the foodborne pathogens tracked by CDC, Listeria monocytogenes had the second highest case fatality rate (21%) and the highest hospitalization rate (90.5%).
FDA’s 2003 Listeria risk assessment of ready-to-eat (RTE) foods identified as high risk vehicles soft unripened cheeses, high fat and other dairy products, pasteurized fluid milk, pâté and meat spreads, smoked seafood and unpasteurized fluid milk, and moderate risk products as cooked RTE crustaceans, deli salads, fermented sausages, reheated frankfurters, fresh soft, soft ripened and semi-soft cheeses, fruits and vegetables.
AMI provides an comprehensive list of backgrounders, including useful documents on Listeria monocytogenes prevention and intervention strategies, as well as the 10 Principles of Sanitary Equipment Design and the recent 11 Principles of Sanitary Facility Design, which identify specific ways that processors can reduce the incidence of microbial contamination of RTE products.
An updated roundup of completed scientific project reports on the prevention and control of Listeria monocytogenes, including research on antimicrobial additives, competitive exclusion microorganisms and composite sampling validation. Useful literature reviews/surveys of the various techniques used in Listeria interventions, including modified atmosphere packaging, high pressure, UV, PEF, irradiation, organic acids, preservatives and ultrasound. Also reviews the foundation’s completed projects on E. coli O157:H7.
The International Fresh-cut Produce Association has posted its Sanitary Equipment Design Buying Guide & Checklist to help fresh-cut produce processors better assess equipment purchases to ensure optimal sanitation, safety and efficiency. Good sanitation is one of the keys to reducing Listeria contamination, and this guide provides a step-by-step look at evaluating the design, fabrication and installation of equipment for food processing that achieve proper sanitation and help reduce the risk of food safety hazards in the plant. The guide includes an extensive list of equipment-related definitions, graphic illustrations of different equipment features and an easy-to-use checklist for evaluating equipment purchases.
CDC estimates that 1.4 million illnesses occur each year in the U.S. from the more than 2,000 strains of Salmonella, with infections associated with this pathogen resulting in more than 16,000 hospitalizations and nearly 600 deaths. Half of salmonellosis cases are caused by two serotypes: S. Enteritidis (SE) and S. Typhimurium (ST). CDC estimated that 118,000 illnesses were caused by consumption of S. Enteritidis-contaminated eggs in 2001. The most common food vehicles for non-typhoid Salmonella are poultry, meat, eggs, milk, and their products. Salmonella has also been detected in chocolate, peanuts, shellfish, alfalfa sprouts, artichokes, beet leaves, celery, cabbage, cantaloupe, cauliflower, chili, cilantro, eggplant, endive, fennel, green onions, lettuce, mungbean sprouts, mustard cress, orange juice, parsley, pepper, salad greens, spinach, strawberries, tomato, and watermelon.
This web page offers links to fact sheets and public comment opportunities pertaining to FDA’s proposed rule for prevention of Salmonella Enteritidis (SE) in shell eggs during production. The proposed regulation would require implementation of SE prevention measures for all egg producers with 3,000 or more laying hens that produce shell eggs for retail sale and do not process their eggs with a treatment, such as pasteurization, to ensure their safety. The proposed rule’s SE prevention measures include: provisions for procurement of chicks and pullets; a biosecurity program; a pest and rodent control program; cleaning and disinfection of poultry houses that have had an environmental sample or egg test positive for SE; refrigerated storage of eggs at the farm; and producer testing of the environment for SE in poultry houses.
FDA posted in June a notice of public meetings on “Produce Safety From Production to Consumption: A Proposed Action Plan to Minimize Foodborne Illness Associated with Fresh Produce Consumption.” This web page summarizes the background of the objectives of the proposed plan to target microbial food safety hazards in or on produce consumed in the U.S., including promoting the application of Good Agricultural Practices and Good Manufacturing Practices (GAP/GMPs) to fresh produce production, using FDA’s Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables or comparable guidance, developing additional guidance applicable to the production of fresh produce, and developing guidance to promote improved hygiene and better preparation practices in the retail environment. The proposed plan would also promote the application of other guidance relevant to fresh produce production, such as FDA’s two guidance documents relating to growing sprouts. Salmonella and E. coli O157:H7 are the most common causes of contamination in sprouts.
An extensive list of links on the latest research, scientific advances, issues, technological process control innovations, and rapid and automated microbiological methods for the enumeration, identification and detection of Salmonella and most of the common pathogens of interest from a wide variety of industry sources. Updated regularly.
Other Pathogens and General Resources
Of course, there are other significant microorganisms, parasites and viruses of concern to the food manufacturer, including Clostridium perfringens associated with outbreaks involving meat, meat stews, meat pies, and beef, turkey, and chicken gravies, beans and seafood; Staphylococcal aureus in sliced meat, poultry, fish, canned mushrooms, dairy products, prepared salad dressing, ham, salami, bakery items and custards; Vibrio vulnificus in oysters and other raw seafood; Shigella found in salads, milk and dairy products, raw vegetables, bakery products, sandwich fillings and poultry; the parasite Toxoplasma gondii in meat, primarily pork; and noroviruses, particularly Norwalk-like, which are associated with cross-contamination of a wide variety of foods, including salad, sandwiches, bakery products, salad dressings and raspberries. Enterobacter sakazakii recently has emerged as a pathogen of concern in powdered infant formulas. In 2004, the World Health Organization estimates that of the one in 100,000 infants made ill, between 20 and 50% of illnesses result in death.
Some useful web resources address many of these microbial food contaminants and more:
The FSIS New Technology Information Table is part of the agency’s effort to encourage the continued innovation in food safety technologies, processes, methods and procedures to improve the safety of meat, poultry, and egg products. The brief summary describes some of the new technologies that FSIS has reviewed, and for which FSIS has had “no objection” to use in FSIS establishments, including antimicrobial washes, treatments, packaging and ingredients, non-intrusive imaging systems for microbial detection, post-packaging and surface pasteurization interventions, and biocides.
Many of the technologies listed have applications in other food categories.
The Institute of Food Technologists’ Scientific Status Summaries are peer-reviewed reports that assess the current state of knowledge on food issues. In July 2004, IFT published the latest report, “Bacteria Associated with Foodborne Diseases,” which reviews the pathogenic significance, association with foods and control measures for the microorganisms historically and newly linked with foodborne illness, excluding enterohemorrhagic E. coli.
The Food Safety Research Consortium’s current backgrounder, “Prioritizing Opportunities to Reduce Foodborne Disease,” details the group’s launch of this new project, funded by USDA/CSREES. The project is part of the FSRC’s long-range program to develop the models and decision tools required to implement a more science- and risk-based approach to food safety, which includes being able to prioritize risk reduction opportunities, taking into account the magnitude of the risk and the feasibility, effectiveness, and cost of possible risk reduction interventions and strategies. The initial framework paper, “Constructing the Analytical Tools for an Integrated, Risk-Based Food Safety System,” is also posted.