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ENVR 430: Foodborne Microbial Disease And Food Safety. Suggested Reading: Brock Chapter 29 – Food Preservation and Foodborne Microbial Diseases pp. 950. E. coli 0157:H7 - Spinach. Date: Tue 19 Sep 2006 Source: FDA.gov
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ENVR 430: Foodborne Microbial Disease And Food Safety Suggested Reading: Brock Chapter 29 – Food Preservation and Foodborne Microbial Diseases pp. 950
E. coli 0157:H7 - Spinach Date: Tue 19 Sep 2006 Source: FDA.gov Case Reports:To date, 131 cases of illness due to _E. coli_ infection have been reported to the Centers for Disease Control and Prevention (CDC), including 20 cases of Hemolytic Uremic Syndrome (HUS), 66 hospitalizations, and one death. Illnesses:Illnesses continue to be reported to CDC. This is considered to be an ongoing investigation. States Affected:There are 21 confirmed states: California, Connecticut, Idaho, Illinois, Indiana, Kentucky, Maine, Michigan, Minnesota, Nebraska, Nevada, New Mexico, New York, Ohio, Oregon, Pennsylvania, Utah, Virginia, Washington, Wisconsin, and Wyoming.
California – another outbreak!! E. COLI O157, UNPASTEURIZED MILK - USA (CALIFORNIA) Date: Fri, 22 Sep 2006 Source: CBS2.com Tainted milk has infected people with _E. coli_ [O157:H7] bacteria, prompting a recall of some milk products, health officials said Fri, 22 Sep 2006. Those infected got sick after drinking unpasteurized milk produced by Organic Pastures, a Fresno County, California dairy, according to the San Diego County Health and Human Services Agency. An 8-year-old San Diego County girl, a Riverside County boy, 7, and a 10-year-old girl in San Bernardino County got sick after drinking the contaminated milk. The state has ordered all Organic Pastures whole and skim raw milk to be pulled immediately from stores and consumers were encouraged to throw away any of the milk in their refrigerators. The recall order also affects raw cream and raw colostrum made by the dairy. Organic Pastures has been prohibited from producing raw milk for the retail market until further notice, officials said. The _E. coli_ outbreak was limited to raw, or unpasteurized milk, county health officials said. Most milk consumed in California is pasteurized, which reduces the risk of getting a bacterial illness.
Date: 2 Nov 2006 Source: CIDRAP (Center for Infectious Disease Research And Policy) News Tomatoes suspected in Salmonella outbreak Federal investigators have turned up few solid leads in a Salmonella outbreak that has sickened 171 people in 19 states, but some food safety experts are suggesting that contaminated tomatoes and infected food service workers might have played a role. The Centers for Disease Control and Prevention (CDC), in a press release yesterday, said DNA fingerprinting revealed that _Salmonella enterica serotype Typhimurium_ caused the outbreak. The organism typically causes fever and nonbloody diarrhea that resolves in a week. Of 73 patients for whom the CDC has clinical data, 14 (19 percent) were hospitalized; no deaths have been reported. The CDC said the outbreak appears to be over: "At this time, few new cases are being detected, and there is little evidence of continuing risk to the public." The agency said the hunt for the source of the outbreak may take days to weeks. The New York Times reported yesterday that the CDC detected the outbreak 2 weeks ago through a national database that identifies patterns in foodborne illness reports. The CDC said cases in the outbreak have been reported since 1 Sep [2006]. Most of the states affected are in the eastern half of the nation. Carlota Medus, PhD, an epidemiologist with the Minnesota Department of Health in St. Paul, said samples from 14 patients in Minnesota matched the outbreak strain on pulsed-field gel electrophoresis (PFGE). She said most of the Minnesota cases occurred between 12 Sep and 13 Oct [2006]. Minnesota, like some of the other states involved in the outbreak, noticed the pattern and contacted the CDC. Medus said a case-control study in Minnesota suggests the contamination source may be tomatoes, adding that 5 cases appear to be linked to the same fast-food restaurant. "Our study is pretty small, though. It would be nice to have more supporting information, so it's a little too soon to say," she said. Jack Guzewich, RS, MPH, director of emergency coordination and response in the Food and Drug Administration (FDA) Center for Food Safety and Applied Nutrition (CFSAN), said _S. Typhimurium_ is the most common strain found in humans and that the CDC usually sees about 5 to 10 cases each month; the numbers usually peak in September and October. "It is found in many places in the food supply, but most often in poultry," he said. Foodborne disease expert Craig W. Hedberg, PhD, an associate professor of environmental health sciences at the University of Minnesota School of Public Health in Minneapolis, called the outbreak fairly significant in its size and scope. "This outbreak is most likely due to tomatoes, and many cases were probably exposed through restaurants," he said, though health officials have not linked the outbreak to a specific product, restaurant, or store. David Acheson, MD, chief medical officer for the FDA's CFSAN, told the Associated Press yesterday that if fresh tomatoes are to blame in the outbreak, it will be more difficult to trace the original source of the contamination than it was in the recent Escherichia coli O157:H7 outbreak linked to fresh spinach. "You can get a lot of information from looking at a bag. You don't get that information from looking at a tomato," he told the AP. During the summer of 2004, three Salmonella outbreaks were traced to contaminated Roma tomatoes. The outbreak sickened 561 people in 18 states and one Canadian province, the CDC said in an April 2005 article in Morbidity and Mortality Weekly Report. Hedberg said a major concern in restaurant-related outbreaks of salmonellosis is the role of infected food handlers in spreading the disease. He said food service workers can become ill from eating the contaminated product and then expose customers to the disease when they are still shedding the organism and don't use proper hygiene practices.
Campus Health Alert - Confirmed E. Coli Cases Among UNC Students (11-6-2006) • In recent days, three University students have developed confirmed cases of gastroenteritis caused by E. coli O157:H7 bacteria. This illness causes severe diarrhea (often bloody), abdominal cramps and is occasionally associated with severe complications, especially in young children and the elderly. The affected students developed symptoms between October 26th and 29th. Health authorities are investigating a small number of additional possible cases among University students. To date, the investigation by public health authorities has not identified any common source of exposure. Currently, there is no indication that other students are at risk. These bacteria usually make people sick within 10 days of exposure. The Orange County Health Department, working in consultation with the North Carolina Communicable Disease Branch, is investigating all of the cases involving the small number of UNC students. Officials from the University's Campus Health Services, Department of Environment, Health and Safety and other offices are monitoring the situation closely and collaborating in the investigation. If you experience severe diarrhea and abdominal cramps, you are encouraged to seek medical attention immediately. • Following is a sampling of general tips from the Centers for Disease Control and Prevention on how you can prevent E. coli infection: • Washing hands frequently and well is the most important thing you can do to avoid bacterial illness. • People with diarrhea should wash their hands carefully with soap after bowel movements to reduce the risk of spreading infection. Anyone with a diarrheal illness should avoid swimming in public pools, sharing baths with others, preparing food for others, providing day care or direct health-care services. • Cook all meat and eggs thoroughly. You can decrease the risk of illness by not eating raw or undercooked meat or eggs. Use a digital instant-read meat thermometer to ensure thorough cooking. • If you are served an undercooked meat or eggs in a restaurant, send it back for more cooking and ask for a clean plate. • Avoid spreading harmful bacteria in the kitchen. Keep raw meat separate from ready-to-eat foods. Wash hands, counters and utensils with hot soapy water after they touch raw meat or eggs. Never place cooked food on the unwashed plate that held raw meat or eggs. Wash meat thermometers in between tests. • Wash fruits and vegetables under running water, especially those that will not be cooked. Bacteria are sticky, so even thorough washing may not remove all contamination. Remove the outer leaves of leafy vegetables. People at high risk of complications from food-borne illness may wish to eat cooked vegetables and peeled fruits.
Foodborne Disease Burden in The United States • Estimated morbidity and mortality: • 76 million illnesses / yr • 325,000 hospitalizations / yr • 5,000 deaths / yr • Estimated costs: • billions $ • loss of consumer confidence • loss of profits Mead et al. (1999) Food-Related Illness and Death in the United States. Emerging Infectious Diseases 5(5):607-625. www.cdc.gov/ncidod/EID/index.htm
OUTBREAKS n = 2,751 CASES n = 86,058 => 29 deaths: 28 confirmed, 1 unknown etiology Number Of Reported Foodborne Disease Outbreaks, Cases, And Deaths, By Etiology, United States (Incl. Guam, Puerto Rico, U.S. Virgin Islands) 1993-1997 Source: Surveillance for Foodborne Disease Outbreaks - United States, 1993-1997 MMWR (2000) 49(SS01):1-51 www.cdc.gov/mmwr
Only a Fraction of Foodborne Illnesses Are Routinely Reported to the CDC • Passive surveillance system • Many diseases not reportable • A complex chain of events must occur to report a foodborne infection to the CDC • Most household foodborne infections are not recognized or reported
Foodborne Disease: Vehicles • Fruits and vegetables and Other salad accounted for highest number of outbreaks • Beef, chicken, and fish also important Most Foodborne Disease of Unknown Etiology
Foods Implicated in Foodborne Illness: Meats Red Meats • High contamination in comminuted and processed meats (e.g. ground beef, sausage) • High surface area, increased contact with processing equipment; increased handling; variety of sources from the animal (organs, trimmings, etc.). • E. coli O157:H7 common etiologic agent in outbreaks assoc. with improperly cooked hamburger and other foods
Foods Implicated in Foodborne Illness: Meats Poultry • High contamination levels in cut‑up poultry • Increased handling, processing and contact with common equipment • Salmonella and Campylobacter are prevalent in poultry flocks • can contaminate an entire processing plant via equipment and process baths (e.g., chiller tank) • Eggs • Endogenous contamination by Salmonella enteritidis in some flocks • Time and temperature abuse leads to proliferation in the egg • Raw / undercooked eggs a source of exposure and infection
Foods Implicated in Foodborne Illness: Fish Contamination depends on type of seafood, quality of harvest water, and amount of processing, handling and storage Bivalve mollusks (oysters, clams, mussels, etc.); filter feeders • Accumulate enteric pathogens from fecally contaminated waters Crustaceans (e.g. crabs, shrimp) • Acquire some pathogens by feeding on mollusks • Acquire high levels of vibrios from their water environment Fin fish • Outer surface and epithelial lining (e.g. gut) contamination by enteric microbes in fecally contaminated waters; • Contamination during processing (e.g., filleting).
Other Foods Implicated in Foodborne Illness Produce (fruits and vegetables) • fecal contamination in irrigation water and other fecal sources (animal droppings, birds, etc.) • inadequate or unsanitary harvesting, washing or processing. Dairy Products • In developed countries milk and related dairy products are usually made from pasteurized milk. • Raw milk and products (e.g., cheeses) made from unpasteurized milk are high risk of bacteria contamination • Salmonella, Campylobacter, Brucella, Yersinia, Listeria
Other Foods Implicated in Foodborne Illness • Unpasteurized fruit juices and other beverages • fecal contamination from animal and human sources • Deli, "Fast" and Restaurant Foods • salads, sandwiches, other fast, deli or restaurant foods • become fecally contaminated during preparation and handling • Cereal and Grain: inadequate storage of cooked rice/grain
Comparison Of # Outbreaks, # Cases, and # Deaths by Food Vehicle (All Etiologic Agents): Shellfish, Poultry, And Produce 1988-1997 OUTBREAKS CASES DEATHS Shellfish 81 2,547 3 Poultry 70 2,707 0 Produce 130 14,805 11 MMWR (1996) 45(SS-5):1-66; MMWR (2000) 49(SS-01):1-51
Foodborne Disease: Etiologic Agents • Most reported outbreaks and cases are caused by bacteria: • Salmonella • Campylobacter • E. coli • Cl. perfringens • Shigella • Staph. aureus • These pathogens were responsible for 22% reportedoutbreaks; 49% cases; 79% deaths from1993-1997
Food Poisoning vs. Food Infection Food poisoning or food intoxication: disease that results from the ingestion of food containing microbial toxins • Microbes that produced the toxins do not have to grow and are often not viable at the time the food is consumed Food infection:active infections resulting from ingestion of pathogen-contaminated foods • Microbes are actively growing in the host • Clinical illness associated with microbial infection, but may also be attributed to toxins produced by the actively growing microbes
Salmonella • Causes an estimated 1.4 million foodborne illnesses / year • Est. 500 deaths / year • Decrease risks for egg-associated infections of S. enteritidis by not eating raw or undercooked eggs • ~40% of persons who died from S. enteritidis were residents of nursing homes; serious disease in others with weakened immune systems • Nursing homes, hospitals, and commercial kitchens should use pasteurized egg products for all recipes requiring pooled or lightly cooked eggs. • Proper egg storage in homes.
Campylobacter jejuni • Causes an estimated 2.5 million foodborne illnesses / year • Among the most common causes of enteric infection in humans overall • Usually mild disease in immunocompetent hosts • for immunocompromised hosts, antimicrobial therapy needed • ~2 in 100,000 diagnosed infections lead to Guillan-Barre syndrome, a paralysis that lasts several weeks • Primary vehicles: milk, poultry, pork • colonization of poultry flocks almost universal; 106-107 cells / processed bird • inadequate cooking, cross-contamination primary causes of infection
Escherichia coli E. coli 0157:H7 (EHEC) Causes at least 60,000 infections and 50 deaths per year Leading cause of kidney failure in children Produces a verotoxin (enterotoxin) similar to Shiga toxin Associated with undercooked meat, particularly ground meat E. coli (ETEC) “travelers diarrhea” Produces two heat-liable enterotoxins Associated with fresh vegetables Also, enteropathogenic (EPEC) and enterinvasive (EIEC) E. coli
Clostridium Anaerobic spore-forming, gram-positive rod; ubiquitous in the environment Clostridium perfringens Most prevalent cause of food poisoning in the US (248,000 cases per year) Perfringens enterotoxin Generally self-limiting Clostridium botulinum Botulism – severe food poisoning Neurotoxin – seven distinct types of botulinum toxin Destroyed by high heat (80oC, 10 m) Associated with foods not cooked after processing; home-canned vegetables, smoked fish vacuum-packed
FOODNET: 1. Active lab-based surveillance 2. Survey of clinical labs 3. Survey of physicians 4. Survey of the population 5. Epidemiologic studies FoodNet also looks for: Listeria monocytogenes Vibrio spp. Yersinia enterocolitica Cyclospora Cryptosporidium www.cdc.gov/foodnet
HOWEVER, Recall that 68% of Reported FBDOs were of Unknown Etiology • Retrospective analysis of clinical data shows that about 50% had incubations period of >15 hours, suggesting viral etiology. Viruses (e.g., Noroviruses; human caliciviruses) are likely a much more important cause of foodborne disease outbreaks than is currently recognized. • Local and state public health programs lack resources and expertise to diagnose viral pathogens, but methods are becoming increasingly available. Viral outbreaks are more likely to be detected in the future.
Human Caliciviruses • ex. Norwalk-like virus(es) • Major agents of foodborne disease. • Outbreaks due to fecally contaminated bivalve mollusks, deli meats, produce, and many other foods. • Relatively persistent in the environment. • Fecal-oral transmission in all age groups; worldwide; direct / indirect contact; secondary spread: common, 25-50%. • Causes acute gastroenteritis: humans are only host; • ~1-2 day incubation period and ~1-4 day duration; • (diarrhea, vomiting, nausea, abdominal pain, anorexia, etc.) • Multiplies in upper small intestine epithelium; blunts microvilli
Hepatitis A Virus (HAV) • Fecal-oral route of exposure • Incubation period: 2-6 weeks • Serious debilitating disease (general infection): fever, abdominal pain, headache, jaundice, nausea, diarrhea • Fecally excreted at concentrations up to 106 infectious units per gram (>109 virions per gram) • Infectious at relatively low doses • Persistent in feces and on foods and environmental surfaces for weeks to months, depending on temperature and other environmental factors. • Heat resistant: requires >60oC for rapid inactivation. • HAV associated with largest documented outbreak of shellfish illness ever recorded: • ~300,000 cases in Shanghai, China 1988 • Traced to consumption of clams harvested from a sewage-polluted area.
Natural Toxins • Toxin: A poison, usually a protein, formed by microorganisms. • Exotoxins are given off as waste products of a microorganism. • Endotoxins are contained within the cells, and are liberated only when the cell dies and disintegrates. Marine Biotoxins • Ciguatera poisoning (fish) • Shellfish toxins (PSP, DSP, NSP, ASP) PSP=paralytic; DSP=diarrheal; NSP=neurotoxic, ASP=amnesic shellfish poisoning • Scombroid poisoning (fish) • Tetrodotoxin (Pufferfish) Fungal And Plant Toxins • Mushroom toxins • Aflatoxins • Pyrrolizidine alkaloids • Phytohaemagglutinin (Red kidney bean poisoning) • Grayanotoxin (Honey intoxication)
Sources of Foodborne Enteric Microbial Contamination Food handler‑associated contamination: inadequate personal hygiene fecal contamination of foods (e.g., hands) Food processing: equipment, packaging, and personnel may contaminate foods during processing
Sources of Foodborne Enteric Microbial Contamination Food storage: time and temperature abuse bacterial growth Fecal contamination prior to harvest or collection: • Animal foods contaminated naturally (e.g., salmonella) • Surface contamination (e.g., feces on fur, feathers, hooves, etc.) • Shellfish and finfish contaminated in their environment • Fecal (sewage) contamination of water pathogen uptake by filter‑feeding on waterborne particles • Fish and shellfish naturally colonized by aquatic pathogens (e.g. Vibrios) • Produce contaminated by irrigation with sewage or contaminated water or fertilization with nightsoil (feces) or animal feces.
Factors Contributing to the Emergence of Foodborne Diseases • Human demographics • -growing segments of the population at • increased susceptibility to infections; ex. elderly • Human behavior • -changes in dietary patterns; ex. increasing consumption • of produce, shellfish • Changes in agricultural industry and technology • -greater geographic distribution of certain types of foods • -mass production, rapid dissemination • Microbial adaptation / evolution • -environmental conditions; antimicrobial resistance • -newly emerging human pathogens • Public health infrastructure • -limited or passive surveillance; monitoring; lack of $$
Microbial Contamination of Foods Food spoilage: any change in the appearance, smell, or taste of a food product that makes it unacceptable to the consumer • May or may not make the food unsafe to eat Foods can be classified into categories with respect to spoilage: • Perishable foods • Semiperishable foods • Stable or nonperishable foods related to their moisture content or water activity
Methods to Control MicrobialContamination of Foods • Prevention: keep enteric microbes out • Remove enteric microbes • Identify and remove contaminated food items and ingredients • Wash to remove contaminants filtration or other physical separation methods • Depurate or relay live shellfish. • Inactivate: kill / destroy microbes • Use of heat • sterilize • disinfect (e.g., pasteurize and cook to destroy pathogens) • Drying, dehydration and intermediate-moisture processing • Chemical treatments: disinfect and sanitize • Irradiation: UV and gamma (ionizing) radiation • Prevent growth of microbes • Use cold and freezing to prevent proliferation
Methods to Control Microbial Contamination of Foods Prevent exposure to fecal contamination in the environment, after harvest or during processing, preparation and handling: Maintain uninfected herds and flocks of animals • Immunize animals against infectious diseases: • Brucella abortus: brucellosis from cattle; raw milk/dairy products • Colonize animals with harmless microflora: • colonize baby chicks with harmless bacteria competitive to Salmonella • Destroy animals harboring pathogens: • Bovine Spongiform Encephalopathy (BSE; “mad cow” disease) • caused by a prion able to infect humans (neural tissue in meat) Maintain sanitation in the environment • harvest shellfish only from waters that are not fecally contaminated • irrigate fruits and vegetables with non‑fecally contaminated water • use uncontaminated fertilizer for fruits and vegetables
Methods to Control Microbial Contamination of Foods Maintain adequate hygiene and sanitation during harvest, processing, storage and distribution • Use clean water for washing, processing, cleaning and worker hygiene • Adequate human and food waste treatment and disposal facilities • Plant and equipment sanitation: clean, sanitize, etc. • Personal hygiene, food handling practices and employee health (education, training and policies) Source control: use of non‑fecally contaminated foods and ingredients • Establish criteria, standards, and guidelines for measuring fecal contamination of foods (pathogens and microbial indicators) • Inspection, monitoring and surveillance (product testing)
Heat and Thermal Treatment Effects of heat vary with food composition and microbe • food composition: water, fat, proteins, carbohydrates, salts and pH • organism factors: form, composition, growth stage, age, etc. Sterilize (or nearly sterilize) foods (destroys all viable microbes) • heat >100oC; usually uses high pressure and steam • typical target temperature is 115‑116oC for about 60 minutes • ex. retorting of canned foods Pasteurization • intended to kill pathogens but does not sterilize the food • often used prior to subsequent cold storage so pathogens or spoilage organisms do not proliferate • High Temperature‑Short Time Method: 72oC; 15 sec. (milk) • Low Temperature‑Long Time Method: 62.8oC for 30 min. (milk) • pasteurization times and temperatures for other foods depend on the effects of heat on the food, food composition and the target organisms of interest
Drying, Dehydration, and Desiccation Low moisture foods: usually <15% moisture Intermediate moisture foods (IMF): 15-50% moisture • fruits, cakes, syrups, candies, jams, milks, some meats and cheeses • Sun (natural) drying: often used for fruits • Heat drying (dehydration; desiccation) • Freeze drying (lyophilization; cryophilization) • Condensing or evaporating: reducing moisture in a liquid food; e.g., evaporated or sweetened condensed milk. Drying destroys some enteric microbes but is not very effective for others
Chemical Treatments Preservatives: • Most are designed to control certain bacteria and molds • Generally, ineffective against viruses and protozoan cysts • Propionates, sorbates, benzoates and p‑hydroxybenzoates: molds • Nitrates and nitrites (ex. for Clostridium botulinum; Cl. perfringens) • Sulfur dioxide and sulfites • Acetic, lactic and other organic acids • NaCl and sugars • Ethylene and propylene oxides Disinfectants and sanitizers: • Used to treat (by washing or dipping) certain meats and produce • Chlorine, peroxyacetic acid, ozone, hydrogen peroxide • Concentrations: 10s to 100s of mg/L; contact times: seconds to minutes • Organic acids (acetic, lactic and citric) at 2-7%; less effective
Food Irradiation Ionizing radiation (X‑rays and gamma rays) • Becoming more widely used • gamma radiation from Co-60 and Cs-137 sources • Effectiveness depends on: organism, composition of the food, temperature, and presence of oxygen • undesirable changes in foods from excessive radiation UV radiation • low (monochromatic 254 nm) and medium (polychromatic) • used primarily for beverages: water, juices, ciders, etc.
Shellfish Depuration and Relaying Place live bivalve mollusks shellfish in clean flowing seawater • normal pumping, feeding and related activity rids accumulated microbes Relaying: • transfer shellfish from contaminated (restricted) waters to uncontaminated natural estuarine waters • typical holding times in the clean water are two weeks or longer Depuration: • Place restricted shellfish in shore‑based tanks of clean, flowing seawater under controlled conditions for periods of several days • Factors influencing deputation efficiency: • tank geometry and loading • water quality • temperature
Hazard Analysis / Critical Control Points (HACCP) A program of process control to (1) identify microbial hazards, (2) identify the most vulnerable (critical) sites or steps in the process and (3) implement an in‑house monitoring system for quality assurance and hygiene. Incorporates elements of: (i) education and training (iv) inspection (ii) ingredient or commodity control (iv) microbiological and (iii) process control related surveys HACCP is designed and implemented on a commodity-specific and production facility-specific basis
Foodborne Safety in the Home • Investigations from outbreaks indicate that consumers do not always take precautions to reduce the risks of foodborne infections • About half of all Salmonellacases result from unsafe handling of food in the home • Many experts believe the kitchen harbors more potentially dangerous bacteria than even the bathroom • Individuals at increased risk and others in the population may be unaware of the risks involved, or of risk-reducing practice(s)
Steps to Prevent Foodborne Illness • Clean: wash hands and surfaces often 2. Separate: don't cross-contaminate 3. Cook: cook to proper temperatures (minimum 160oF) 4. Cool / chill: refrigerate promptly (refrigerator= 41oF)
Study Points: • What are the three leading foods associated with illness? • Food poisoning vs. food infection • Agents of disease: • Bacteria • Campylobacter • Salmonella • E. coli • Clostridium • Viruses • Noroviruses • Hepatitis A virus • Sources of food contamination • Methods to control contamination • Thermal, chemical, desiccation, irradiation, etc. • HACCP • Steps to prevent foodborne illness in the home