Foodborne zoonoses
1 / 93

FOODBORNE ZOONOSES Over 250 diseases can be caused by ... - PowerPoint PPT Presentation

  • Uploaded on

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

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'FOODBORNE ZOONOSES Over 250 diseases can be caused by ...' - benjamin

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Foodborne zoonoses l.jpg

  • 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

Foodborne zoonoses2 l.jpg

  • 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

Foodborne zoonoses4 l.jpg

  • Major virulence determinants:

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

    • exotoxins

    • endotoxins

  • enzymes - assist bacteria in establishing infection and producing disease

Foodborne zoonoses5 l.jpg


  • 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

Foodborne zoonoses6 l.jpg


  • 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

Foodborne zoonoses7 l.jpg


  • 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

Foodborne zoonoses8 l.jpg


  • 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

Foodborne zoonoses9 l.jpg


  • 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

Foodborne zoonoses10 l.jpg

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

Foodborne zoonoses11 l.jpg

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

Foodborne zoonoses12 l.jpg

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)

Foodborne zoonoses13 l.jpg

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

Foodborne zoonoses14 l.jpg

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

Foodborne zoonoses15 l.jpg

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

Foodborne zoonoses16 l.jpg

  • Escherichia coli O157:H7

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

  • Listeria monocytogenes

  • Salmonella spp. (Enteriditis; Typhimurium)

  • Yersinia enterocolitica; Y pseudotuberculosis

Escherichia coli l.jpg
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

Categories of escherichia coli causing diarrhea l.jpg
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)

Escherichia coli o157 h7 l.jpg
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

Escherichia coli o157 h720 l.jpg
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)

Escherichia coli o157 h721 l.jpg
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

Escherichia coli o157 h722 l.jpg
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)

Escherichia coli o157 h723 l.jpg
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

Escherichia coli o157 h724 l.jpg
Escherichia coli O157:H7

Epidemiological features

  • Reservoir:

    • cattle especially young dairy cattle

    • wild ruminants - deer (?)

    • humans

Escherichia coli o157 h725 l.jpg
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)

Escherichia coli o157 h726 l.jpg
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

Escherichia coli o157 h727 l.jpg
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

Escherichia coli o157 h728 l.jpg
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

Escherichia coli o157 h729 l.jpg
Escherichia coli O157:H7

Clinical features

  • diarrhea ranging from mild, non-bloody to virtually

  • straight bloody stool, abdominal cramping

  • fever is infrequent

Escherichia coli o157 h730 l.jpg
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)

Escherichia coli o157 h731 l.jpg
Escherichia coli O157:H7

Clinical features

  • Thrombotic thrombocytopenic purpura (TTP) in elderly

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

Escherichia coli o157 h732 l.jpg
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

Escherichia coli o157 h733 l.jpg
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

Escherichia coli o157 h734 l.jpg
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

Escherichia coli o157 h735 l.jpg
Escherichia coli O157:H7

Control methods

  • treatment

    • fluid/electrolyte replacement

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

Campylobacter enteritis l.jpg
Campylobacter enteritis


  • 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)

Campylobacter enteritis37 l.jpg
Campylobacter enteritis


  • 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

Campylobacter enteritis38 l.jpg
Campylobacter enteritis


Gram stain from culture media

(Note slender, curved rods)

Campylobacter enteritis39 l.jpg
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

Campylobacter enteritis40 l.jpg
Campylobacter enteritis


  • 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

Campylobacter enteritis41 l.jpg
Campylobacter enteritis


  • Mode of transmission:

    • vehicles:

      • undercooked meat

      • contaminated food and water

      • raw milk

    • direct contact: pets, farm animals, infected infants

    • person-person uncommon

Campylobacter enteritis42 l.jpg
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

Campylobacter enteritis43 l.jpg
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

Campylobacter enteritis44 l.jpg
Campylobacter enteritis


  • 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)

Salmonellosis l.jpg

  • 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

Salmonellosis46 l.jpg

  • 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)

Salmonellosis47 l.jpg

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

Salmonellosis48 l.jpg

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

Salmonellosis49 l.jpg

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

Salmonellosis50 l.jpg

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

Salmonellosis51 l.jpg

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

Salmonellosis52 l.jpg

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)

Salmonellosis53 l.jpg

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

Salmonellosis54 l.jpg

  • 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

Salmonellosis55 l.jpg

  • 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

Salmonellosis56 l.jpg

  • 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

Salmonellosis57 l.jpg

  • 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

Salmonellosis58 l.jpg

  • Prevention and control

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






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

Salmonellosis59 l.jpg

  • 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

Salmonellosis60 l.jpg

  • 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

Salmonellosis61 l.jpg

  • 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

Listeriosis l.jpg

  • 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

Listeria monocytogenes l.jpg
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%)

Listeria monocytogenes64 l.jpg
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

Listeria monocytogenes65 l.jpg
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)

Listeria monocytogenes66 l.jpg
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

Listeria monocytogenes67 l.jpg
Listeria monocytogenes

  • Epidemiological features

    • Susceptibility and resistance

      • fetuses, newborns are highly susceptible

      • older aged, immunocompromised individuals

      • acquired immunity unlikely

Listeria monocytogenes68 l.jpg
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

Listeria monocytogenes69 l.jpg
Listeria monocytogenes

  • Epidemiological features

    • Mode of transmission

      • direct contact

      • neonatal

        • transmitted in utero

        • during passage through infected birth canal

        • contaminated equipment in nurseries

Listeria monocytogenes70 l.jpg
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)

Listeria monocytogenes71 l.jpg
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)

Listeria monocytogenes72 l.jpg
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

Listeria monocytogenes73 l.jpg
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

Listeria monocytogenes74 l.jpg
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

Listeria monocytogenes75 l.jpg
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

Listeria monocytogenes76 l.jpg
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

Listeria monocytogenes77 l.jpg
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

Listeria monocytogenes78 l.jpg
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

Listeria monocytogenes79 l.jpg
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

Listeria monocytogenes80 l.jpg
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

Listeria monocytogenes81 l.jpg
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)

Listeria monocytogenes82 l.jpg
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

Listeria monocytogenes83 l.jpg
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

Yersiniosis l.jpg

  • Organisms:

    • Yersinia enterocolitica

    • Y. pseudotuberculosis

  • Other names for disease:

    • Intestinal yersiniosis

    • Extraintestinal yersiniosis

Yersiniosis85 l.jpg

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

Yersiniosis86 l.jpg

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

Yersiniosis87 l.jpg


  • 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

Yersiniosis88 l.jpg


  • 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

Yersiniosis89 l.jpg

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)

Yersiniosis90 l.jpg

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”

Preventing food borne disease l.jpg
Preventing food-borne disease

  • Fight BAC!

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

      • Clean

      • Separate

      • Cook

      • Chill

Preventing food borne disease92 l.jpg
Preventing food-borne disease


    • 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

Preventing food borne disease93 l.jpg
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