FOODBORNE ZOONOSES

1
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

2
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

3
FOODBORNE ZOONOSES
4
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

5
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

6
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

7
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

8
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

9
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

10
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

11
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

12
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 O157H7

14
FOODBORNE ZOONOSES

• Surveillance programs
• Antimicrobial resistance surveillance
• PulseNet - network set up for molecular subtyping
• pulsed-field gel electrophoresis method for E.
  coli O157H7 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

15
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

16
FOODBORNE ZOONOSES

• Escherichia coli O157H7
• 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

18
Categories of Escherichia coli causing diarrhea

• enterohemorrhagic (EHEC - hemorrhagic colitis
  O157H7)
• enterotoxigenic (ETEC- travelers diarrhea)
• enteroinvasive (EIEC - dysentery-like)
• enteropathogenic (EPEC - infant diarrhea)
• enteroaggregative (infant d. in underdeveloped
  countries)
• diffuse-adherence (pediatric diarrhea)

19
Escherichia coli O157H7

• 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

20
Escherichia coli O157H7

• 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 (O26H11 O111H8 O104H21)

21
Escherichia coli O157H7

• 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

22
Escherichia coli O157H7

• Microbiological features and identification
• most enterohemorrhagic (EHEC) strains of E. coli
  do not ferment sorbitol (MacConkey-sorbitol media
  used for screening O157H7)
• presence of Shiga-like toxins
• serotyping (phage typing)

23
Escherichia coli O157H7

• 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

24
Escherichia coli O157H7

• Epidemiological features
• Reservoir
• cattle especially young dairy cattle
• wild ruminants - deer (?)
• humans

25
Escherichia coli O157H7

• 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 O157H7

• Epidemiological features
• Incubation period
• relatively long, ranging from 3-8 days
• Period of communicability
• may be up to three weeks in children
• prolonged carriers uncommon

27
Escherichia coli O157H7

• Epidemiological features
• Susceptibility and resistance
• very low infectious dose
• old-age appears to be a risk factor
• children developing hemolytic-uremic syndrome

28
Escherichia coli O157H7

• 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 O157H7

• Clinical features
• diarrhea ranging from mild, non-bloody to
  virtually
• straight bloody stool, abdominal cramping
• fever is infrequent

30
Escherichia coli O157H7

• 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)

31
Escherichia coli O157H7

• Clinical features
• Thrombotic thrombocytopenic purpura (TTP) in
  elderly
• Case fatality rate 3-5 (up to 50 in elderly
  with TTP)

32
Escherichia coli O157H7

• 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

33
Escherichia coli O157H7

• Control methods
• preventive measures to reduce incidence
• adequately cook meat to a temp of 155F (68C)
• 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

34
Escherichia coli O157H7

• 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

35
Escherichia coli O157H7

• Control methods
• treatment
• fluid/electrolyte replacement
• antibiotic treatment uncertain TMP-SMX may lead
  to hemolytic-uremia syndrome

36
Campylobacter enteritis

• Background
• Significant cause of enteritis worldwide and of
  travelers diarrhea in U.S.
• Leading cause of bacterial diarrhea in U.S.
• Campylobacter 45
• Salmonella 30
• Shigella 17
• E.coli O157H7 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 biotypes and 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)
39
Campylobacter enteritis

• Clinical features
• watery diarrhea, sometimes with blood (occult)
• normally self-limiting, not requiring treatment
• most common in children ((15-29 yrs of age)
• low fatality rate--usually in immunocompromised
• infective dose small (500 organisms in some
  cases)
• toxin production may cause diarrhea

40
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

41
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

42
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 O157H7)
• Consumer proper food handling procedures in
  kitchen
• 1 HACCP Hazard Analysis and Critical Control
  Point

43
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

44
Campylobacter enteritis

• Outbreaks
• Usually outbreaks are small (
• 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
• 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

48
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

49
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

50
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

51
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

52
SALMONELLOSIS

• Epidemiology - disease frequency
• case fatality rate
• 15 with S. dublin reported in elderly
• up to 4 with S. enteriditis (nursing homes,
  hospital associated outbreaks with most being
  elderly)

53
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

54
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

55
SALMONELLOSIS

• Clinical features
• chronic disease
• small percentage of cases develop Reiters
  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

56
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

57
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

58
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

59
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

60
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

61
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

62
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
  1980s

63
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)

64
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

65
Listeria monocytogenes

• Microbiological features and identification
• aerobic, microaerophillic
• growth on simple media (blood, trypticase soy
  agar) or selective media (McBrides agar)
• cold-enrichment techniques - too time consuming
  once recognized as a food pathogen
• now have faster methods - FDA (dairy products)
  USDA (meat products)

66
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

67
Listeria monocytogenes

• Epidemiological features
• Susceptibility and resistance
• fetuses, newborns are highly susceptible
• older aged, immunocompromised individuals
• acquired immunity unlikely

68
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

69
Listeria monocytogenes

• Epidemiological features
• Mode of transmission
• direct contact
• neonatal
• transmitted in utero
• during passage through infected birth canal
• contaminated equipment in nurseries

70
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)

71
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)

72
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

73
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

74
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

75
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

76
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

77
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
• storage of milk at low temperatures (shipping

78
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

79
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

80
Listeria monocytogenes

• Control
• Storage
• temperature is a major factor affecting the risk
  of multiplication
  prevent, multiplication
• storage times of food should be kept to a minimum

81
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 (

82
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

83
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

84
Yersiniosis

• Organisms
• Yersinia enterocolitica
• Y. pseudotuberculosis
• Other names for disease
• Intestinal yersiniosis
• Extraintestinal yersiniosis

85
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

86
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

87
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

88
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

89
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)

90
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

91
Preventing food-borne disease

• Fight BAC!?
• Partnership for Food Safety Education program
  aimed at educating food handlers and food
  preparers
• Clean
• Separate
• Cook
• Chill

92
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

93
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