Food Microbiology 1

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Food Microbiology 1
Unit 3 Food borne Pathogens II
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Infection
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Bacteria That Cause Infection

• Campylobacter jejuni
• Salmonella
• Listeria monocytogenes
• Yersinia

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Campylobacter jejuni

• Gram negative spiral curved rod
• Non-spore forming
• Microaerophilic (low oxygen) i.e. 3-8 Oxygen,
  15 CO2
• Growth Temperature 32-45oC, optimum is 42oC
  (body temperature of chickens)

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Campylobacter jejuni

• In the intestinal tract of warm-blooded animals
• Does not survive well outside the host and does
  not grow well in food

Initial contamination levels are more important
than storage conditions

• Fastidious nutrient requirements
• Sensitive to oxidative stress
• Normally present in low numbers in foods
• Can be isolated from patients diarrhea at
  relatively high levels

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• Less than 500 organisms are thought to be enough
  to cause illness in humans
• Colonizes the mucosal surface of the lower
  intestinal tract
• Motility permits access through mucus to
  epithelial cells
• Invasion of epithelial cells results in
  inflammatory enteritis

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Symptoms

• Incubation period (from ingestion till first
  sign) 2-5 days
• Abdominal pain/cramps
• Headache, Diarrhea (sometimes bloody)
• Nausea and sometimes vomiting
• Fever, chills
• Case fatality rate is 0.1 to 0.2
• Duration is approximately 1 week

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Further complications

• Meningitis
• Guilian- Barré syndrome
• - ascending paralysis leading to
  respiratory muscle paralysis and death
• The number one bacteria causing food borne
  illness

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Sources

• Found in foods of animal origin, water and
  sewage
• Commonly found in birds (chicken)
• 80 of poultry carry Campylobacter
• 90-100 of organic poultry produced carry
  Campylobacter
• Birds, cattle and pigs show no symptoms
• Humans can be symptomless carriers

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Foods Implicated

• Undercooked poultry and meats
• Raw Milk
• Contaminated Water
• Raw Clams

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Prevention

• Adequate cooking of poultry
• Minimize cross-contamination between cooked and
  raw foods
• Wash hands and work surfaces after handling raw
  foods
• Pasteurize milk
• Chlorinate water

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Salmonella

• Facultative anaerobes, Gram-negative, motile
  rods with peritrichous flagella, highly invasive
  and spread easily
• Salmonellosis disease caused by bacteria in this
  genus
• Salmonella Enteritidis PT4 most pathogenic in
  chickens and predominated
• Temperature for growth 5-45oC (35-37oC)
• Min pH 4.5
• Min aw 0.97

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• Contamination from eggs and broiler meats
• Trans-ovarian before eggs formed.
• Trans-shell infection invade the egg
  through
• the shell after eggs laid
• Estimated 1 of the population diagnosed with
  Salmonella yearly
• Infected birds are symptomless, eggs laid
  appear normal
• They may survive the hard-cooking process
  (Hard-cooked eggs associated with two recent
  outbreaks)
• Infective dose for Salmonellae is believed to be
  less than 103 CFU/ml

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Salmonella Cycle
Contaminated feed, environment, insects, rodents,
spread from infected birds, etc
Colonization in intestinal tract
Invasion into internal organs
Fecal Shedding
Broilers
Breeders
Layers
Hatching eggs
Poultry Meat
Infected chicks
Table Eggs
Infected pullets
Contaminated eggs or meat
Human enteritis
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• Invades small intestine and colon by entering
  absorptive mucosal cells and mucosa associated
  macrophages
• Grow inside fixed macrophages of liver and spleen

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Frequent Serotypes Associated with Food borne
Illness

• Salmonella Typhimurium
• Salmonella Enteritidis
• Salmonella Dublin

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Symptoms

• Typhoid or paratyphoid fever from Salmonella
  typhi and Salmonella paratyphi
• Salmonellosis

• Headache
• Fever and chills
• Diarrhea, cramps
• Nausea
• Vomiting

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Salmonella

• Symptoms usually occur 12 to 24 hours after
  ingestion of the contaminated food
• Period of illness is 1-3 days
• Infected individuals can carry and shed
  Salmonella for months
• Infected persons can show no symptoms but carry
  and spread the organism. E.g. Typhoid Mary

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Typhoid Mary

• Mary Mellon
• A house cook in 1906 in New York
• She was a symptomless carrier of Salmonella
• Infected 33 people
• Eventually she was sent to jail to protect the
  public!

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Sources of Salmonella

• Inhabitant of intestinal tract of animals,
  birds, reptiles, insects
• Garden soil survives for 250 days
• Liquid manure for 27-286 days
• Slurry for 84 to 250days
• Infected feces stored in cans for 159 days

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Factors Contributing to outbreaks

• Improper cooling
• lapse of a day or more between preparation and
  serving
• Inadequate cooking or heat processing
• Ingestion of contaminated raw ingredients
• Cross-contamination

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Associated Foods

• Poultry
• Eggs and Egg products
• Meat and meat products
• Un-pasteurized milk and dairy products
• Vegetables and sprouted seeds

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Prevention

• Vaccine programs and screening significantly
  reduce numbers in poultry and eggs
• Cook food products sufficiently (no sunny
  side-up eggs)
• Avoid cross-contamination between raw and cooked
  foods