Food- and Waterborne diseases

1
Food- and Waterborne diseases

• Causes
• Roles of microbes
• Contributing factors

2
Three overlapping groups of GI disorders

• Pathogenic microbes and toxins that they form
  (most common)
• Algae and parasites
• Other
• Toxins formed from breakdown of food
• Toxic chemicals
• Allergens
• Digestive or nutritional disorders

3
Investigating foodborne disease

• Regulatory agencies (USDA, FDA, CDC)
• Outbreak two or more people get sick from eating
  the same food (with the same symptoms)
• Chemical poisoning, highly fatal disease one
  case is enough

4
Major pathogens (in terms of cost)

• Campylobacter jejuni
• Clostridium perfringens
• E. coli O157H7
• Listeria monocytogenes
• Salmonella
• Staphylococcus aureus
• Toxoplasma gondii

5
Categories of microbial infection

• Intoxication (toxin is preformed)
• Infection (microbes can grow in body)
• Toxicoinfection (organisms ingested, die, and
  release toxins)
• Opportunistic pathogens

6
Major pathogens associated with foodborne diseases

• Intoxication
• C. botulinum highest mortality
• S. aureus most cases
• Pathogens
• Salmonella, Listeria monocytogenes
• Toxicoinfection
• C. perfringens, followed by B. cereus
• Viral diseases
• Hepatitis, Norwalk-type viruses

7
Why certain foods?

• Raw vs finished foods
• Food environment favors the growth of a pathogen
• Quality control is lacking
• More handling

8
Predominant food types

• Meats- Salmonella S. aureus
• Egg products- Salmonella
• Fish- Salmonella, C. botulinum
• Fruits and vegetables- C. botulinum
• Processed meats, unpasteurized milk- L.
  monocytogenes
• Salmonella is ubiquitous

9
Incidence of foodborne illness

• Restaurants, fast-food, cafeterias, schools
• High volume, much handling
• Homes
• Improper cooling and storage, cross-contamination
• Outings (picnics, etc.)
• Mishandling, temperature abuse
• Commercial preparation- outbreaks rare, but can
  affect large numbers of people

10
Factors contributing to outbreaks from pathogenic
bacteria and viruses

• Improper refrigeration most common factor
  (according to data from 1980s)
• Poor personal hygiene
• Survival of pathogens due to improper cooking
• Cross-contamination
• Unsafe food sources

11
Tis the season

• Foodborne outbreaks more common during the summer
  months
• Why do you think so?
• Regional conditions
• Migration patterns
• Different susceptibilities to disease (age,
  general health, immune status)
• Innate virulence of pathogen

12
FoodNet established 1996

• Objectives
• Determine frequency and severity of foodborne
  diseases
• Trace foodborne diseases to specific foods
• Determine the epidemiology of new bacterial,
  viral, parasitic pathogens
• Use epidemiological studies and surveillance of
  outbreaks to reduce foodborne illnesses (are
  initiatives working?)

13
Nine pathogens evaluated over 10-year period
(1996-2005, gt 25 million persons)

• Campylobacter ssp.- declined 30
• Salmonella- decreased, then increased
• Shigella ssp.- decreased 43
• E. coli O157H7 -decreased 29
• Listeria monocytogenes- decreased 32
• Yersinia enterocolitica decreased 43
• Vibrio spp. increased 41
• Cryptosporidia much fluctuation unchanged
  overall
• Cyclospora- unchanged
• Highest incidence (Salmonella) ca 14 per 100,000
  populaiton

14
Is foodborne illness underreported?

• Studied surveillance and reporting systems like
  FoodNet (Mead et al., Emerg. Infect Dis, 1999)
• Total number of foodborne illness from known and
  unknown causes 76 million
• Known pathogens accounted for about 25 of all
  foodborne illnesses
• 75 of deaths caused by Salmonella, Listeria, and
  Toxoplasma
• Not all outbreaks can be documented accurately
• Some cases are sporadic, some outbreak
• Some pathogens are transmitted by food, but also
  other sources
• Answer yes

15
Foodborne intoxications features

• Can be produced while pathogen is growing in food
  or preformed (presence of viable microbes not
  always necessary)
• May be heat sensitive or heat stable
• Onset of symptoms may be very rapid (30 minutes)
• Fever not usually produced
• Toxins tend to affect body systems (enterotoxins,
  neurotoxins)

16
Staphylococcus aureus
Gram-positive coccus Transmitted from skin and
hair (by handling) Multiplies in foods held at
room temperature Toxin does not affect food
quality More than 17 enterotoxins Heat
stable Stimulates vagus nerve, induces
vomiting Grows in a wide variety of foods
Microbiologyinpictures.org
Citizendick.org
17
Neurotoxins Clo. botulinum (Gram-positive
anaerobe)

• Foodborne
• Preformed spreads from intestines to peripheral
  nerves
• Infant- ingestion of spores
• Hidden- in feces but food source unknown
• Wound- anaerobes can grow in deep wounds
• Inadvertent- BoTox gone awry

18
Mycotoxicosis Secondary metabolites, not
toxins Can be carcinogenic, Hallucinogenic
(ergot) Aflatoxin Aspergillus species liver
damage
Air.ky.gov
19
Foodborne infections

• Live cells are consumed and penetrate gut lining
• Produce toxins and/or cause cell damage
• Does levels vary greatly
• Symptoms usually occur after 24 hours
• Some can spread out of the digestive system

20
Salmonellosis

• Most common cause of foodborne illness- and most
  persistent
• Carrier state persists after recovery
• Inflammation leads to loss of fluid and diarrhea
• Associated with wide variety of foods
• Gram-negative rod, non-lactose fermenting

21
Listeriosis

• Recently recognized as foodborne pathogen-
  oppotunistic?
• Psychrotroph- can grow in refrigerators, so
  low-level contamination can increase
• Highly fatal to young, old, pregnant, immune
  compromised
• Zero tolerance because of high fatality rate

22
Listeriosis forms of disease

• Febrile gastroenteritis
• High infectious dose
• Flu-like symptoms
• Bacteria shed for weeks or months in feces
• Invasive systemic disease
• Infectious dose of 100-1000
• Passes through intestines into body can affect
  liver, brain, placenta

23
Listeriosis is usually sporadic

• Strict controls in place for ca 20 years
• High-risk people told to avoid soft cheeses and
  ready-to-eat foods without heating
• Rapid testing possible with serological methods

24
Pathogenic E. coli

• Most E. coli are harmless and at very high levels
  in intestines
• Six groups can cause disease
• Enterotoxigenic (ETEC)
• Travelers diarrhea toxin no inflammation high
  dose required
• Enteropathogenic (EPEC)- infant diarrhea
• Enteroinvasive (EIEC)-dysentery (bloody diarrhea)
• Enterohemorrhagic(EHEC)- bloody diarrhea and HUS
  (hemorrhagic uremic syndrome)
• Shiga-like toxin kills cells
• Enteroaggregative (EAEC)
• Diffuse-adhering (DAEC)

25
Toxicoinfections

• Spore formers cells do not multiply but form
  spores and release toxins
• Clostridium perfringens (meats)
• Bacillus cereus (variety of foods)
• Gram-negative cells multiply, or die and release
  toxins
• Vibrio cholerae- contaminated food and water
• ETEC- fecally contaminated food and water

26
Opportunistic pathogens or toxins

• Dont normally cause disease
• Breakdown products of proteins
• Algal toxins (Gonyaulax catenella)
• Parasites (worms and protozoans)

27
New and emerging food borne pathogens

• Are they really new, or newly confirmed?
• Pathogens can increase or decrease as causative
  agents for illness
• Food consumption patterns
• Changes in food processing and marketing
• Changes in agricultural practices
• Migration of food and people
• Health of individuals

28
More knowledge of pathogens

• Many are discovered in large outbreaks
• Campylobacter jejuni
• EHEC O157H7
• Listeria monocytogenes, among others
• More data
• New testing technology
• Regulatory practices, education

29
Food habits

• More seafood, more vibrio and hepatitis
• More low-heat-processed foods stored longer
• More consumption of raw foods
• Fruits, vegetables, and juices organisms
  modified to low-pH and low temperature
  environments
• New pathogens
• Hepatitis E
• H. pylori
• BSE
• Aeromonas

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Summary

• Foodborne illness has been recognized for
  centuries
• New pathogens are regularly added to the list-
  and this will continue
• Illness may be sporadic or due to an outbreak
• Much is known about many organisms, their
  symptoms, and the onset of disease
• Not everyone reacts to exposure the same way