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FOODBORNE ZOONOSES Over 250 diseases can be caused by contaminated food or drink most are bacterial ( Salmonella and Campylobacter) or caused by Norwalk virus most cases are single cases, not associated with a recognized food-borne outbreak

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FOODBORNE ZOONOSES

  • Over 250 diseases can be caused by contaminated food or drink

  • most are bacterial (Salmonella and Campylobacter) or caused by Norwalk virus

  • most cases are single cases, not associated with a recognized food-borne outbreak

  • majority of food items are raw or undercooked products of animal origin (meat, dairy, poulty, seafood)

  • ~ 500 outbreaks reported each year


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FOODBORNE ZOONOSES

  • Foodborne illness a substantial problem in US

    • 6.5 to 33 milliion cases annually

    • ~9000 deaths

  • Since 1986, of ~3200 outbreaks reported, only 21 were associated with contaminated produce

  • Reporting of food- and water-borne diseases began over 50 years ago as investigations of enteric fevers



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FOODBORNE ZOONOSES

  • Major virulence determinants:

  • toxins - destroy, damage, inactivate natural defense mechanism of host

    • exotoxins

    • endotoxins

  • enzymes - assist bacteria in establishing infection and producing disease


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FOODBORNE ZOONOSES

Toxins

  • exotoxins

    • secreted from cell or leak out after cell death

    • soluble protein, thus readily carried through body by lymphatics or blood

    • damage at distant site, usually specific

    • normally destroyed by heating to 100º C., although some are resistant to boiling (S. aureus)

    • non-pyrogenic

    • example: botulinism toxin, Staphylococcus aureus


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FOODBORNE ZOONOSES

Toxins

  • endotoxins

    • produced only by gram negative bacteria

    • part of the outer cell wall (lipopolysaccharide coat)

      • lipid A component is toxic

      • side chains (O, H antigen) are immunogenic

    • released in large amounts at cell death

    • heat stable, not destroyed by autoclaving

    • less potent and less specific than exotoxins


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FOODBORNE ZOONOSES

Toxins

  • endotoxins

    • pyrogenic

    • toxic to most animals, producing similar range of biological effects regardless of source

      • fever

      • increased WBC

      • DIC (disseminate intravascular coagulopathy)

      • hypotension

      • shock

      • death

    • degraded by oxidizing agents

    • examples: E. coli, Salmonella, Shigella


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FOODBORNE ZOONOSES

Enzymes

  • spreading factors

    • hyaluronidase (gram +) - attacks interstitial cement of connective tissue

    • collagenase (Clostridium) - break down collagen, facilitating invasion of muscle and gas gangrene formation

    • neuraminidase (Vibrio and Shigella) - break down intercellular cement of intestinal epithelial cells

    • kinase (Strep and Staph) - digests fibrin, preventing clotting and allowing rapid diffusion


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FOODBORNE ZOONOSES

Enzymes

  • cell lysis

    • hemolysins (Staph, Strep, and Clostridia)

    • lecithinases (C. perfringens)

    • phospholipases (C. perfringens) -  toxin

  • coagulase (Staph) - causes clotting

  • adenylate cyclase activity - bacterial toxins having immediate (short-range) effects that promote invasion

    • Ex: anthrax toxin - edema factor


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FOODBORNE ZOONOSES

New challenges

  • newly identified pathogens (emerging pathogens)

  • newly identified vehicles of transmission

  • changes in food production

  • changes in food distribution

  • decline in food safety awareness


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FOODBORNE ZOONOSES

Reasons for emergence or re-emergence

  • changes in pathogen

  • centralized and concentrated production

  • globalization of food supply

  • increase in “at risk” populations

  • changes in food animal practices

  • changes in type and volume of foods imported

    • now import over 30 billion tons of food annually

    • change in dietary preferences and exposure has led to many more types of produce being introduced


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FOODBORNE ZOONOSES

Surveillance programs

  • Foodborne Disease Active Surveillance Network (FoodNet) by CDC-EIP

    • collaboration with USDA, FDA

    • to determine incidence of foodborne illness in US

    • established in 7 locations:

      • California (selected counties)

      • Connecticut (selected counties)

      • Georgia (selected counties)

      • Minnesota (entire state)

      • Oregon (entire state)

      • New York (selected counties)

      • Maryland (selected counties)


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FOODBORNE ZOONOSES

Surveillance programs

  • FoodNet (continued)

    • to document effectiveness of Hazard Analysis and Critical Control Points Rule (HACCP)

    • active surveillance

      • population survey

      • physician survey

      • case-control study of E. coli O157:H7


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FOODBORNE ZOONOSES

Surveillance programs

  • Antimicrobial resistance surveillance

  • PulseNet - network set up for molecular subtyping

    • pulsed-field gel electrophoresis method for E. coli O157:H7 now available in 24 state laboratories, along with USDA and FDA

    • rapid comparison of PFGE profiles with database at CDC

    • already been critical in outbreak investigation in Colorado associated with ground beef and multi-state investigation traced to alfalfa sprouts

  • Basic research at NIH

    • establish virulence mechanisms and develop prevention tools


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FOODBORNE ZOONOSES

Surveillance programs

  • Enter-Net (formerly Salm-Net)

    • European Commission funded

    • Established for surveillance for Salmonella and E. coli infections

    • Includes 15 European countries

    • has already let to public health interventions and product recalls in Europe


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FOODBORNE ZOONOSES

  • Escherichia coli O157:H7

  • Campylobacter spp. (jejuni; fetus ssp. fetus)

  • Listeria monocytogenes

  • Salmonella spp. (Enteriditis; Typhimurium)

  • Yersinia enterocolitica; Y pseudotuberculosis


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Escherichia coli

  • gram-negative rod-shaped bacteria

  • hundreds of strains

  • most strains are harmless, normal intestinal flora of healthy humans and animals

  • occurrence: ubiquitous, worldwide distribution


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Categories of Escherichia coli causing diarrhea

  • enterohemorrhagic (EHEC - hemorrhagic colitis; O157:H7)

  • enterotoxigenic (ETEC- traveler’s diarrhea)

  • enteroinvasive (EIEC - dysentery-like)

  • enteropathogenic (EPEC - infant diarrhea)

  • enteroaggregative (infant d. in underdeveloped countries)

  • diffuse-adherence (pediatric diarrhea)


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Escherichia coli O157:H7

  • first recognized in 1982 outbreak of hemorrhagic diarrhea traced to hamburgers (fast food chain)

  • estimated 10,000 to 20,000 cases/yr in the US

  • outbreaks have been associated with other foods such as leaf lettuce, cider, contaminated water

  • more commonly isolated than Shigella


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Escherichia coli O157:H7

  • “O” and “H” designation refer to cell surface antigen markers that are used to distinguish serotypes

  • Other serotypes of enterohemorrhagic strains may also be implicated (O26:H11; O111:H8; O104:H21)


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Escherichia coli O157:H7

  • syndrome caused by potent cytotoxins: verotoxins 1 and 2 (Shiga-like toxins I and II because resemble toxins of Shigella dysenteriae)

  • may also produce hemolytic-uremic syndrome

  • although recognized and intensively studied for 15 years, still do not know best method of treatment nor how animals become infected


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Escherichia coli O157:H7

  • Microbiological features and identification

    • most enterohemorrhagic (EHEC) strains of E. coli do not ferment sorbitol (MacConkey-sorbitol media used for screening O157:H7)

    • presence of Shiga-like toxins

    • serotyping (phage typing)


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Escherichia coli O157:H7

  • Microbiological features and identification

    • identification of toxin genes by DNA probes

    • presence of virulence plasmid (plasmid allows expression of a fimbria, attachment to the intestinal mucosa)

    • does not grow well or at all at 44-45ºC


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Escherichia coli O157:H7

Epidemiological features

  • Reservoir:

    • cattle especially young dairy cattle

    • wild ruminants - deer (?)

    • humans


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Escherichia coli O157:H7

Epidemiological features

  • Transmission:

    • ingestion of contaminated foods

      • usually inadequately cooked beef (especially ground beef)

      • raw milk

      • other foods by cross-contamination--lettuce, apple cider, apple juice

    • person-person (families, child care facilities, institutions)

    • waterborne (swimming in crowded areas, drinking water)


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Escherichia coli O157:H7

Epidemiological features

  • Incubation period:

    • relatively long, ranging from 3-8 days

  • Period of communicability:

    • <1 week in adults

    • may be up to three weeks in children

    • prolonged carriers uncommon


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Escherichia coli O157:H7

Epidemiological features

  • Susceptibility and resistance

    • very low infectious dose

    • old-age appears to be a risk factor

    • children < 5 years of age are at greatest risk of developing hemolytic-uremic syndrome


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Escherichia coli O157:H7

Epidemiological features

  • Occurrence

    • important cause of foodborne disease in US, UK, Europe, Japan, South Africa, southern regions of South America, Australia

    • importance in underdeveloped regions and rest of world not established


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Escherichia coli O157:H7

Clinical features

  • diarrhea ranging from mild, non-bloody to virtually

  • straight bloody stool, abdominal cramping

  • fever is infrequent


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Escherichia coli O157:H7

Clinical features

  • Hemolytic-uremia syndrome

    • more common in children

    • may occur in up to 10% of cases

    • characterized by:

      • hemolytic anemia

      • thrombocytopenia

      • renal failure (common cause of renal failure in children)


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Escherichia coli O157:H7

Clinical features

  • Thrombotic thrombocytopenic purpura (TTP) in elderly

  • Case fatality rate: 3-5% (up to 50% in elderly with TTP)


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Escherichia coli O157:H7

Control methods

  • Preventive measures to reduce incidence

    • slaughterhouse management to minimize contamination of meat by intestinal contents

    • pasteurization of milk and dairy products

    • irradiate beef, especially ground beef


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Escherichia coli O157:H7

Control methods

  • preventive measures to reduce incidence

    • adequately cook meat to a temp of 155°F (68°C)

      • ‘pink all gone’ does not mean necessarily safe - cooking with meat thermometer is recommended

    • protect, purify, chlorinate public water supplies for drinking

    • chlorination of swimming pools

    • adequate hygiene in day-care facilities


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Escherichia coli O157:H7

Control methods

  • control of patient and immediate environment

    • report to health department (mandatory in many states)

    • isolation: because of extremely small infective dose, patients should not be allowed to handle food or provide child/patient care until 2 negative samples are obtained

    • disinfection

    • contacts with diarrhea should be handled as if infected (no food handling, no patient care or child contact) until two negative fecal samples are obtained


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Escherichia coli O157:H7

Control methods

  • treatment

    • fluid/electrolyte replacement

    • antibiotic treatment uncertain; TMP-SMX may lead to hemolytic-uremia syndrome


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Campylobacter enteritis

Background

  • Significant cause of enteritis worldwide and of traveler’s diarrhea in U.S.

  • Leading cause of bacterial diarrhea in U.S.

    • Campylobacter 45%

    • Salmonella 30%

    • Shigella 17%

    • E.coli O157:H7 5%

  • Most common isolate: C. jejuni (C. fetus ssp. jejuni)


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Campylobacter enteritis

Microbiology

  • Campylobacter jejuni; C. colio, C. fetus ssp. fetus, C. spp.

  • many biotypesand serotypes occur; useful in epidemiology

  • gram-negative, microaerophillic, motile rods

  • distinct shape of organism, flagella useful in identification

  • require special environmental conditions for optimal growth

    • 5% O2

    • prefers relatively high concentration of CO2

  • relatively fragile, sensitive to stresses such as oxygen, drying, heat, acidic conditions


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Campylobacter enteritis

Microbiology

Gram stain from culture media

(Note slender, curved rods)


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Campylobacter enteritis

Clinical features

  • watery diarrhea, sometimes with blood (occult)

  • normally self-limiting, not requiring treatment

  • most common in children (<5 yrs) and young adults (15-29 yrs of age)

  • low fatality rate--usually in immunocompromised

  • infective dose small (~500 organisms in some cases)

  • toxin production may cause diarrhea


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Campylobacter enteritis

Epidemiology

  • Occurrence: estimated 2 - 4,000,000 cases/yr in US, probably more

  • Reservoir:

    • poultry and cattle primarily; also pets, swine, and other species

    • common contaminant of raw poultry (20-100% at retail)

    • can exist in intestinal tract of people and animals without causing symptoms

    • present in high numbers in stools of infected symptomatic individuals


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Campylobacter enteritis

Epidemiology

  • Mode of transmission:

    • vehicles:

      • undercooked meat

      • contaminated food and water

      • raw milk

    • direct contact: pets, farm animals, infected infants

    • person-person uncommon


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Campylobacter enteritis

Prevention and control

  • On the farm: good sanitary practices (USDA guidelines)

  • In the plant: HACCP1 to minimize opportunity for spread

  • At retail: recall policy on ready-to-eat meat and poultry products found to be contaminated enforced by USDA (similar for E. coli O157:H7)

  • Consumer: proper food handling procedures in kitchen

    1 HACCP = Hazard Analysis and Critical Control Point


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Campylobacter enteritis

Prevention and control

  • CDC report: 80% of US outbreaks due to Campylobacter could be prevented with universal pasteurization of milk and proper treatment of drinking water

  • improved handling of chicken important

  • bacteria destroyed when meat/poultry reach internal temperature of 160º F

  • freezing not reliable method for destroying organism but thorough cooking will render product safe


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Campylobacter enteritis

Outbreaks

  • Usually outbreaks are small (< 50 individuals)

  • Vermont: 2,000 people ill from temporary use of non-chlorinated water supply

  • 1986 outbreak in school children traced back to milk which was being pasteurized for 135º F for 25 minutes rather than the required 145º F for 30 minutes (LTLT)

    • Note: 161º F for 15 seconds (HTST)

      280º F for 2 seconds (ultra-pasteurized)


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SALMONELLOSIS

  • Causative organisms: primarily S. enteriditis, typhimurium in U.S.

  • numerous serotypes, many are pathogenic to both animals and man

  • of the ~2,000 serotypes known, only ~200 recognized in the U.S.

  • discovered in 1880, genus named for American scientist Salmon in honor of his extensive work


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SALMONELLOSIS

  • Microbiological features and identification

    • gram-negative rod-shaped bacteria

    • motile (non-motile forms are S. gallinarium, pullorum)

    • heat labile

    • growth prevented at <7º C for most serotypes

    • non-spore forming, but can survive for long periods in foods and other substrates

    • can survive for long periods in foods with low aw (water activity) such as chocolate, peanut butter, black pepper)


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SALMONELLOSIS

Epidemiology - reservoir

  • ubiquitous

  • found in a wide range of animals, particularly poultry, swine, cattle, pets (iguanas, turtles, terrapins, tortoises, chicks, dogs, cats), humans

  • chronic carriers common in animals and birds, less so in humans

  • S. enteriditis infects ovaries of healthy appearing hens, thereby contaminating eggs in oviduct before shell is formed


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SALMONELLOSIS

Epidemiology - reservoir

  • S. typhi, paratyphi - man only

  • S. typhimurium - animals, particularly food animals

  • S. enteriditis - animals, particularly food animals

  • S. dublin - cattle

  • S. choleraesuis - swine

  • S. gallinarum, pullorum - poultry

  • S. arizonae - animals, reptiles


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SALMONELLOSIS

Epidemiology - mode of transmission

  • ingestion of raw, undercooked, or contaminated food

    • meat, milk, eggs, produce

  • fecal-oral transmission

    • contact with pets (especially infants)

    • foods contaminated by infected food handler

  • outbreaks usually traced to food items


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SALMONELLOSIS

Epidemiology - disease frequency

  • incidence highest in infants and young children

  • estimated 5 million cases annually (US)

    • up to 80% are sporadic cases

    • large outbreaks in hospitals, restaurants, institutions are common

  • largest outbreak in US (25,000 cases) resulted from a nonchlorinated municipal water supply


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SALMONELLOSIS

Epidemiology - disease frequency

  • proportion of reported cases due to S. enteriditis has increased from 5% in 1976 to 26% in 1994

  • report in J of Infectious Diseases (1994) - 82% of outbreaks due to S. enteriditis between 1985-1991 were traced to contaminated shell eggs


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SALMONELLOSIS

Epidemiology - disease frequency

  • case fatality rate

    • <1% for most forms of salmonellosis

    • 15% with S. dublin reported in elderly

    • up to 4% with S. enteriditis (nursing homes, hospital associated outbreaks with most being elderly)


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SALMONELLOSIS

Selected outbreaks in US

  • 1985 - 16,000 cases in 6 states

    • low fat and whole milk from a Chicago dairy

    • pasteurization process changed, resulting in contamination of pasteurized milk with raw milk

    • persons on antibiotic therapy more likely to be affected

  • 1984 - ~2700 passengers affected on 29 flights

    • caused by S. enteriditis

    • strongly associated with food in First Class section only


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SALMONELLOSIS

  • Clinical features

    • generally, salmonellosis is a milder disease than typhoid/paratyphoid

    • acute disease

      • nausea, vomiting, cramping, diarrhea, fever, headache

      • more severe, even life-threatening disease can occur in infants, elderly, immunocompromised


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SALMONELLOSIS

  • Clinical features

    • chronic disease

      • small percentage of cases develop Reiter’s syndrome

        • arthritic pain, irritation of eyes, painful urination

        • can last for months to years, leading to chronic arthritis refractive to treatment

        • antibiotic therapy does not seem to prevent development of this serious sequela to acute salmonella infection


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SALMONELLOSIS

  • Clinical features

    • incubation period: variable - 12 to 72 hours

    • illness generally lasts 4-7 days

    • disease is caused by penetration and passage of organisms from gut lumen into epithelium; enterotoxin production (?)

    • infective dose:

      • as few as 15-20 cells depending on strain (4 serotypes ingested in vehicles that buffer gastric acids)

      • normally >102-3


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SALMONELLOSIS

  • Diagnosis

    • serological identification of culture isolated from stool

  • Food analysis

    • developed for many foods

    • conventional methods - 5 days for presumptive results

    • rapid methods require only 2 days


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SALMONELLOSIS

  • Prevention and control

  • FDA: ‘farm-to-table’ actions to reduce food safety risks associated with shell eggs

    farm

    slaughter

    processing

    retail

    consumer

  • 1 in 20,000 eggs produced annually contain S. enteriditis


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SALMONELLOSIS

  • Prevention and control

    • FDA/FSIS pending proposals

      • 38 states require refrigeration at retail level

      • voluntary quality assurance programs for egg producers

        • cleaning/disinfecting hen houses

        • rodent control

        • proper egg washing

        • refrigeration between transport and storage

        • biosecurity measures

        • monitoring chick mortality

        • use of SE free chicks and pullets


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SALMONELLOSIS

  • Control

    • processing - control of factors such as pH, moisture, presence of preservatives should me assessed at all stages using systematic approach (HACCP)through transit, storage, foodservice, and retail levels

    • storage at low temperatures - most serotypes fail to grow below 7ºC

    • retail

      • handwashing

      • avoid food preparation by workers with diarrhea

      • thoroughly cook all poulty, pork, meat, egg dishes

      • strict sanitation practices in kitchen, including rodent and insect control


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SALMONELLOSIS

  • Control

    • consumer control

      • FDA Recommendations

        • avoid consumption of raw eggs

        • avoid cross-contamination - clean utensils, disinfect surfaces, proper hygiene, separate cutting surfaces for raw and cooked meats and vegetables

        • thoroughly cooking meat, poultry, eggs (71ºC)

        • do not freeze eggs in shell

        • store cooked eggs in refrigerator, discard after 1 week

      • recognize risk in pets (chicks, ducklings, and reptiles)--not recommended for small children


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LISTERIOSIS

  • Causative organism: Listeria monocytogenes

  • common inhabitant of intestine, soil, silage, other environmental sources

  • most are pathogenic to some degree

  • not recognized as a food-borne pathogen until the 1980’s


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Listeria monocytogenes

  • Microbiological features and identification

    • gram-positive rod-shaped

    • motile, flagellated

    • non spore-forming

    • will grow at pH 4.4 - 9.6

    • will grow in high salt concentrations (>10%)


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Listeria monocytogenes

  • Microbiological features and identification

    • resistant to heat, freezing, drying

      • able to grow at temperatures as high as 50ºC and as low as 3ºC (psychotrophic - able to grow at refrigerator temperatures)

      • freezing has little detrimental effect on the organism


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Listeria monocytogenes

  • Microbiological features and identification

    • aerobic, microaerophillic

    • growth on simple media (blood, trypticase soy agar) or selective media (McBride’s agar)

    • cold-enrichment techniques - too time consuming once recognized as a food pathogen

      • now have faster methods - FDA (dairy products); USDA (meat products)


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Listeria monocytogenes

  • Epidemiological features

    • Reservoir

      • ubiquitous

      • primary reservoir is soil, silage, environment

      • also present in intestinal tract of animals and humans; asymptomatic carriers common (up to 10%)

      • seasonal use of silage followed by increase in number of listeriosis cases in livestock


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Listeria monocytogenes

  • Epidemiological features

    • Susceptibility and resistance

      • fetuses, newborns are highly susceptible

      • older aged, immunocompromised individuals

      • acquired immunity unlikely


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Listeria monocytogenes

  • Epidemiological features

    • Mode of transmission

      • foodborne - outbreaks associated with ingestion of raw or contaminated food

        • milk (raw and supposedly pasteurized), cheeses (particularly soft-ripened), ice cream, raw vegetables, fermented raw-meat sausage, raw and cooked poultry, raw meat, raw and smoked fish


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Listeria monocytogenes

  • Epidemiological features

    • Mode of transmission

      • direct contact

      • neonatal

        • transmitted in utero

        • during passage through infected birth canal

        • contaminated equipment in nurseries


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Listeria monocytogenes

  • Epidemiological features

    • Frequency of disease

      • in US - ~1,850 cases annually

      • case fatality rate: 425 deaths annually

        • 30% in newborn infants

        • up to 50% when onset within first 4 days

        • nonpregnant - recent epidemic 35% (63% in >60 yrs of age)


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Listeria monocytogenes

  • Epidemiological features

    • Risk factors

      • pregnancy (20 times more likely to get listeriosis); 33% of cases occur during pregnancy

      • newborns - more likely to suffer serious effects

      • immunocompromised (AIDS, CA, diabetes, renal disease, elderly)


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Listeria monocytogenes

  • Epidemiological features

    • source of infection in selected outbreaks

      • Maritime Provinces (Canada) - coleslaw made from cabbage fertilized with sheep manure; 28% CFR

      • California (1985) - Mexican-style cheese, numerous stillbirths; 142 cases, 33% CFR; FDA now monitors all domestic and imported cheeses

      • many cases are sporadic, now thought to be foodborne, associated with soft cheese (Brie, Camembert, etc.)

      • jellied pork tongue - cause of 279 cases, 63 deaths, 22 abortions in France in 1992


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Listeria monocytogenes

  • Clinical features

    • Target population

      • pregnant women/fetus

      • Cancer patients

      • immunocompromised (AIDS, steroid therapy, graft suppression therapy)

      • elderly

      • healthy individuals - low risk

        • antacids and H2 blockers may predispose to infection

        • outbreak among healthy individuals in Switzerland involving heavily contaminated cheese


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Listeria monocytogenes

  • Clinical features

    • incubation period: variable - 3 to 70 days

    • signs and symptoms:

      • flu-like symptoms

      • septicemia

      • meningitis or meningoencephalitis

      • encephalitis

      • intrauterine or cervical infections

      • spontaneous abortion (2nd or 3rd trimester)

      • gastrointestinal symptoms (nausea, vomiting, diarrhea)

    • onset time varies: few days to 3 weeks in serious disease, > 12 hours in more mild forms


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Listeria monocytogenes

  • Clinical features

    • infective dose varies with strain; foodborne disease occurs with less than 1,000 organisms in susceptible individuals (immunocompromised, elderly)

    • invades monocytes, macrophages, PMN leukocytes, hence name and pathogenesis (transplacental and access to brain tissue)

    • “circling disease” and abortions in cattle, sheep, and goats


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Listeria monocytogenes

  • Diagnosis

    • isolation from CSF, blood, amniotic fluid, placenta, gastric washings

    • growth on routine media

    • serology unreliable

  • Food analysis

    • FDA method (1990) requires 5-7 days for identification

    • use of specific DNA probes should afford faster and less complicated confirmation of isolates


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Listeria monocytogenes

  • Control

    • Prevention of listeriosis begins on the farm and continues through processing and handling by the consumer

      • On the farm:

        • silage production controlled to achieve rapid acidification (pH <4.0)

        • storage of milk at low temperatures (<5ºC) until shipping


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Listeria monocytogenes

  • Control

    • Processing

      • control of factors such as pH, moisture, presence of preservatives should me assessed at all stages using systematic approach (HACCP)

      • measures to prevent contamination through transit, storage, foodservice, and retail levels


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Listeria monocytogenes

  • Control

    • Three major objectives of processing control

      • minimize growth and multiplication of organism in raw foods, particularly before and during processing

      • use of appropriate products to assure destruction of organism

      • minimize risk of recontamination of ready-to-eat products


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Listeria monocytogenes

  • Control

    • Storage

      • temperature is a major factor affecting the risk of multiplication; <5ºC will retard, but not prevent, multiplication

      • storage times of food should be kept to a minimum


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Listeria monocytogenes

  • Control

    • Consumer control

      • avoid cross-contamination - clean utensils, disinfect surfaces, proper hygiene, separate cutting surfaces for raw and cooked meats and vegetables

      • thaw food in the refrigerator, then keep refrigerated but only for short period, then discard

      • serve foods hot (>60ºC) or cold (<4ºC)


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Listeria monocytogenes

  • Control

    • Consumer control

      • potentially unsafe foods should not be kept between 4ºC - 60ºC more than 4 hours between buying and eating

      • thoroughly cooking meat (71ºC), poultry (85ºC), seafood

      • thorough scrubbing of vegetables, do not cook too far in advance since this increase likelihood of bacterial growth


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Listeria monocytogenes

  • Recent multistate outbreak, 1998-1999

    • at least 50 cases caused by a rare strain of Listeria monocytogenes (serotype 4b)

    • reported to CDC by 11 states

    • onset August 2 - December 13, 1998

    • vehicle for transmission: hot dogs and possibly deli meats under several brands but all by same manufacturer: Bil Mar Foods

    • massive product recall in OH, NY, TN, MI, MA, VT, GA, MN, WI, MO, AK, AL, CT, OR


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Yersiniosis

  • Organisms:

    • Yersinia enterocolitica

    • Y. pseudotuberculosis

  • Other names for disease:

    • Intestinal yersiniosis

    • Extraintestinal yersiniosis


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Yersiniosis

Microbiological features

  • Gram-negative bacilli

  • Growth: microaerophillic, psychrotrophic

  • Motility at 25ºC - Y pseudotuberculosis

  • Serotypes

    • Y enterocolitica: >50 (5 biotypes)

    • Y pseudotuberculosis: 6 (4 subtypes)

    • O3; O8 strains most common in US


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Yersiniosis

Microbiological features

  • Virulence plasmid mediated – invasion factors (unknown)

  • Growth preference primarily extracellular

  • CIN agar (cefsulodin-irgasan-novobiocin) – selective medium for optimal growth of Yersinia organisms


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Yersiniosis

Epidemiology

  • Reservoir

    • Y enterocolitica – swine, other animals

    • Y pseudotuberculosis – wild and domestic animals including canine and feline pets

  • Occurrence

    • Ubiquitous worldwide

    • Both species may account for up to 3% of acute gastroenteritis in some areas

    • Infants (Y entercolitica), children and young adults (both species) most susceptible

    • CDC estimates ~17,000 cases annually; normally associated with outbreaks


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Yersiniosis

Epidemiology

  • Mode of transmission

    • fecal-oral by ingestion of contaminated food or water as a result of poor sanitation and improper handling

    • associated with pork, seafood, raw milk

    • Recent outbreaks

      • Tofu

      • Chitterlings

      • Pasteurized milk in contaminated milk cartons


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Yersiniosis

Clinical features

  • Incubation period: 24-48 hrs

  • Signs/symptoms

    • Acute gastroenteritis (enterocolitis)

      • diarrhea (80%)

      • abdominal pain

      • Fever

    • Acute lymphadenitis (mesenteric nodes) in lower right quadrant — mimics appendicitis

    • Erythema nodosum (~10%)

    • Arthritis (post-infection)


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Yersiniosis

Clinical features

  • Diagnosis

    • Isolation of organism from feces, blood

    • Biochemical confirmation

    • Serologic – acute and convalescent sera

  • Complications

    • Fatalities rare

    • Unnecessary appendectomies

    • Reactive arthritis in up to 3% of cases even in the absence of symptoms

    • Bacteremia – transient “carrier state”


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Preventing food-borne disease

  • Fight BAC!

    • Partnership for Food Safety Education program aimed at educating food handlers and food preparers

      • Clean

      • Separate

      • Cook

      • Chill


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Preventing food-borne disease

  • HACCP

    • Hazard Analysis and Critical Control Point

      • USDA/FSIS program implemented in all plants processing meat and poulty

      • Pathogen reduction standards for Salmonella and E coli

      • Implementation began in 1997, to be completed as of Jan 2000


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Preventing food-borne disease

  • Food Compliance Programs

    • FDA/CFSAN (Center for Food Safety Applied Nutrition)

    • Issued for 3 years; re-issued every three years or more frequently as needed

    • Guidance for inspection, investigation, administration

    • Apply to imported and domestic products

      • Acidified/low-acid canned foods

      • Milk and cheese products

      • Drug residue in milk

      • Milk safety

      • Mycotoxins

      • Medical foods

      • Infant formulas


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