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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

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E. coli 0157:H7 - Spinach

Date: Tue 19 Sep 2006Source: 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.

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E. coli 0157:H7 - Spinach

Date: Thu, 21 Sep 2006Source: CNN.com Health authorities hunting the source of a nationwide _E. coli_ [O157:H7] outbreak are focusing on 9 California farms after discovering what could be a crucial clue: an opened bag of spinach left in the refrigerator of someone sickened by the bacteria. The bag of tainted Dole baby spinach is the "smoking gun" that has allowed investigators to zero in on 3 counties in California's greater Salinas Valley, said Dr. Mark Horton, the state public health officer. Authorities also were checking processing plants, Horton said. Officials said consumers still shouldn't eat bagged spinach, even as they closed in on the source of the bacteria as likely somewhere in Monterey, San Benito or Santa Clara counties. The bag of fresh spinach that tested positive for _E. coli_ was found in New Mexico, and other bags recovered elsewhere in the country also were being tested. "It's certainly premature to say only this bag is going to test positive," said Dr. David Acheson of the FDA's Center for Food Safety and Applied Nutrition. "There are others in the works." New Mexico Department of Health officials confirmed the tainted bag of spinach was found after a person who ate some of the leafy greens became 1 of 146 people in 23 states sickened by the outbreak, and 1 person has died. The spinach tested positive for the same strain of _E. coli_ linked to the outbreak, Acheson said. Dole is one of the brands of spinach recalled Friday by Natural Selection Foods LLC of San Juan Bautista, California.

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Spinach E.Coli Source: Wild Pigs On Monterey Ranch(CBS 5 / AP / BCN) MONTEREY 10/26/2006Wild pigs at a single ranch in the Monterey-San Benito county area may have spread deadly bacteria onto a California spinach field, sparking an outbreak that killed three people and sickened more than 200 others nationwide in recent months, investigators said Thursday. They also said the outbreak appears to be over. No one has become ill from eating contaminated spinach since Sept. 25. "All evidence points to this outbreak having concluded," said Dr. Kevin Reilly of the California Department of Health Services. "The outbreak appears to be over at this point." State and federal investigators have narrowed their focus to the ranch, where boars trampled fences that had hemmed in a spinach field. Samples taken from a wild pig, as well as from stream water and cattle on the ranch, have tested positive for the same strain of E. coli implicated in the outbreak, Reilly said. He cautioned, though, that the investigation into the E. coli outbreak remains ongoing and investigators have not completely ruled out the possibility that the bacteria contaminated the spinach somewhere else. "We are not saying this is the source at this point," Reilly said of the ranch. However, he said nine samples of the same E. coli strain as in the outbreak were found in various places on or near the one ranch. "All these findings ... have been found on the same ranch," Reilly said. "All of the specimens were between one-half mile and one mile from the spinach field.“ The outbreak sickened 204 people in 26 states and one Canadian province, he said. Wild pigs are one "real clear vehicle" that could explain how E. coli spread from cattle on the ranch to the spinach field less than a mile away, Reilly said. The pigs could have tracked the bacteria into the field or spread it through their droppings. "I think we have good evidence" pointing to feral pigs as the vehicle that transported the bacteria to the spinach fields, Reilly said. Investigators also are looking at runoff, flooding, irrigation water, fertilizer and other wildlife, including deer, as possible sources. Reilly refused to give a specific location for the ranch, other than to say it's in a valley in the area of San Benito and Monterey counties. Investigators first recovered the same strain of bacteria earlier this month from three cattle manure specimens collected on the ranch. On Thursday, Reilly said the strain had been isolated from six other samples collected on the ranch, including from cattle. The finds mark the first time that investigators have identified a possible source for any of the multiple E. coli outbreaks linked to the heavily agricultural area. Still, investigators continue to look at three other ranches in the area in seeking the source of the contaminated fresh spinach. Investigators have taken roughly 750 samples from the four ranches. They've found generic E. coli on all four ranches the bug is commonly found in cattle but turned up the particular strain involved in the outbreak on only one. "We have no evidence to suggest people should not be eating spinach from other places except from these four ranches," said Jack Guzewich, of the Food and Drug Administration's Center for Food Safety and Applied Nutrition.

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E. COLI VTEC NON-O157, LETTUCE - USA (UTAHDate: Thu 30 Aug 2006Source: Monterey Herald Utah health officials say Salinas Valley lettuce may be responsible for an _E. coli_ outbreak in their state in June 2006 that sickened 73 people, including 3 who developed kidney failure. The announcement comes just 2 days after federal and state regulators began inspecting local lettuce fields, plants and coolers in response to an increase in lettuce-related _E. coli_ outbreaks over the past decade. The iceberg lettuce was served in salads from a Wendy's restaurant in North Ogden, Utah, which catered a teachers' conference at a junior high school. Just where between field and fork the lettuce was contaminated is unknown, Utah health officials said. In the past decade, said the FDA, more than 400 people nationwide have been sickened in leafy-produce-related _E. coli_ outbreaks, including 2 people who died. Investigations into these outbreaks, often done weeks and months after they occur, rarely reveal how or when the lettuce is tainted. In response, federal and state regulators this week began the unprecedented monitoring of the local industry, which produces at least 75 percent of the nation's lettuce. At least 2 women, one who ate salad at the conference and one who didn't attend the conference but ate a hamburger with lettuce from the same restaurant, experienced serious complications. One of the women is now on a kidney transplant list. The other was on dialysis for several weeks and nearly had to have her large intestine removed. The outbreak involved _E. coli_ O121:H19, a rare form of the bacteria that normally live in the intestines of humans and animals. Most _E. coli_ outbreaks connected to leafy greens in the past decade have involved the 0157:H7 strain. Officials from the Weber-Morgan Health Department in Utah said they narrowed their focus on the lettuce because it was the only food that all of the sickened people ate. Wendy's International spokesman Denny Lynch stressed on Tue, 29 Aug 2006, that the lettuce in question wasn't tested following the outbreak. Instead, health officials are using patients' eating histories to deduce what carried the bacteria, he said. "There is no confirmation there was lettuce because there was nothing to test," Lynch said. Two days before the outbreak, Lynch said, the Wendy's in North Ogden passed a routine health inspection "with flying colors." Once the company learned about the outbreak, it asked the health department to come back to the restaurant for an inspection, and nothing inappropriate was found, he said.

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E. COLI O157, UNPASTEURIZED MILK - USA (CALIFORNIA)Date: Fri, 22 Sep 2006Source: 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.

California – another outbreak!!

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SALMONELLOSIS, SEROTYPE TYPHIMURIUM - USA (MULTISTATE)Date: Tue 31 Oct 2006Source: CDCThe CDC, in collaboration with state departments of health and the FDA, is investigating an outbreak of infections caused by a type of salmonella called _Salmonella_ [enterica_ serotype] Typhimurium. This infection has no relationship to typhoid fever, which is caused by another organism. Serotype Typhimurium typically causes an illness with fever and non-bloody diarrhea, which commonly resolves after about one week. This illness is different from that caused by _E. coli_ O157:H7, which produces bloody diarrhea, severe cramps, and in some persons, severe kidney disease. PulseNet, the network of public health laboratories that performs molecular subtyping [DNA fingerprinting?] on bacteria that cause foodborne illnesses, has identified a specific strain of _S._ Typhimurium that has caused this outbreak. Cases caused by the specific strain have been detected regularly at low frequency (average, 86 cases per year) for the past 5 years, indicating the presence of this strain at low levels in the environment and the food chain. The outbreak has involved 171 cases of infection by this strain in 19 states reported since 1 Sep 2006. The median age of patients is 36 years, and 59 percent are female. As with most infections by salmonella, most patients had a febrile diarrheal illness. Of 73 patients for whom clinical data has been reported, 14 (19 percent) were hospitalized; there have been no deaths reported. At this time, few new cases are being detected, and there is little evidence of continuing risk to the public. CDC and its public health partners are vigorously working to identify the specific contaminated food or foods that caused this outbreak. Outbreaks from a widely distributed contaminated food cause cases to be scattered across the country, and the identity of the contaminated food is often not readily apparent. In outbreaks like this one, identification of the contaminated food requires conducting detailed standardized interviews with recovering case-patients and with non-ill members of the public to compare the foods they had eaten. Using statistical methods, the contaminated food is identified as one eaten more commonly by case-patients than the controls. This statistically-based method of identifying contaminated foods is routinely supplemented and confirmed by laboratory testing of foods. The process is labor intensive and may require days to weeks. As soon as the contaminated food is identified, if there is evidence of ongoing risk, public health officials can advise the public to avoid it and remove the food from the marketplace. Precise information on avoiding infection with the outbreak strain of salmonella will be provided by CDC as soon as the contaminated food(s) is identified.

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Date: 2 Nov 2006Source: CIDRAP (Center for Infectious Disease Research And Policy) News Tomatoes suspected in Salmonella outbreakFederal 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.

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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: 

1.Washing hands frequently and well is the most important thing you can do to avoid bacterial illness. 2.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. 3.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. 4.If you are served an undercooked meat or eggs in a restaurant, send it back for more cooking and ask for a clean plate. 5.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. 6.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.

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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

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OUTBREAKSn = 2,751

CASESn = 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, 1993-1997MMWR (2000) 49(SS01):1-51

www.cdc.gov/mmwr

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Only a Fraction of Foodborne Illnesses Are Routinely Reported to the CDC

1. Passive surveillance system

2. Many diseases not reportable

3. A complex chain of events must occur to report a foodborne infection to the CDC

4. Most household foodborne infections are not recognized or reported

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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

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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

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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

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Foods Implicated in Foodborne Illness: Fish

Contamination depends on type of seafood, quality of harvestwater, 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).

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Other Foods Implicated in Foodborne IllnessProduce (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

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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

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Comparison Of # Outbreaks, # Cases, and # Deaths by Food Vehicle (All Etiologic Agents):

Shellfish, Poultry, And Produce 1988-1997

OUTBREAKS CASES DEATHSShellfish 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

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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% reported outbreaks; 49% cases; 79% deaths from 1993-1997

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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

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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.

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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

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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

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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

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www.cdc.gov/foodnet

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

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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.

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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

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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.

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Natural Toxins

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)

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.

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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

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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.

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•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 $$

Factors Contributing to the Emergenceof Foodborne Diseases

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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:

1) Perishable foods2) Semiperishable foods3) Stable or nonperishable foods

related to their moisture content or water activity

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Methods to Control MicrobialContamination of Foods

1. Prevention: keep enteric microbes out2. 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.

3. 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

4. Prevent growth of microbes– Use cold and freezing to prevent proliferation

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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 animals1. Immunize animals against infectious diseases:

• Brucella abortus: brucellosis from cattle; raw milk/dairy products

2. Colonize animals with harmless microflora: • colonize baby chicks with harmless

bacteria competitive to Salmonella3. 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 environment1. harvest shellfish only from waters that are not fecally contaminated2. irrigate fruits and vegetables with non‑fecally contaminated water3. use uncontaminated fertilizer for fruits and vegetables

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Methods to Control Microbial Contamination of Foods

Maintain adequate hygiene and sanitation during harvest, processing, storage and distribution

1. Use clean water for washing, processing, cleaning and worker hygiene

2. Adequate human and food waste treatment and disposal facilities3. Plant and equipment sanitation: clean, sanitize, etc.4. Personal hygiene, food handling practices and

employee health (education, training and policies)

Source control: use of non‑fecally contaminated foods and ingredients

1. Establish criteria, standards, and guidelines for measuring fecal contamination of foods (pathogens and microbial indicators)

2. Inspection, monitoring and surveillance (product testing)

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Heat and Thermal TreatmentEffects 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

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Drying, Dehydration, and Desiccation

Low moisture foods: usually <15% moistureIntermediate 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 butis not very effective for others

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Chemical TreatmentsPreservatives:

– 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

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Food IrradiationIonizing 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.

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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

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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

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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 Salmonella cases 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)

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Steps to Prevent Foodborne Illness

1. 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)

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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