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Foodborne Pathogen and Disease
Foodborne Pathogens
a biological infectious agent (Microorganism)
that causes Foodborne illness to host (referred
to as food poisoning) is any illness resulting from
the consumption of contaminated food.
Foodborne Pathogens:
• Foodborne pathogens are the leading causes of
illness and death in less developed countries
killing approximately 1.8 million people annually.
• In developed countries foodborne pathogens are
responsible for millions of cases of infectious
gastrointestinal diseases each year, costing
billions of dollars in medical care and lost
productivity.
• New foodborne pathogens and foodborne
diseases are likely to emerge driven by factors
such as pathogen evolution, changes in
agricultural and food manufacturing practices,
and changes to the human host status.
• There are growing concerns that terrorists could
use pathogens to contaminate food and water
supplies in attempts to incapacitate thousands of
people and disrupt economic growth.
Pathogenic microorganisms
1. Intoxication :
- Staphylococcus aureus
- Clostridium botulinum
- Bacillus cereus
2. Infection :
- Salmonella
- Clostridium perfringens
- Vibrio
- Phathogenic E.coli
Staphylococcus aureus
TAXONOMY
• Gram positive coccus (producing an exotoxin)
Source of contamination of food
- nose and skin of humans and animals
- high level in people with
- skin infection
- heavily colonised skin disease
• Contamination by food handler
• Eliminated by pasteurization
• Microwave decreases counts
• Fat/ sugar/ salt protects the organism
• Usually about 106 / g needed to produce
sufficient toxin
• Generally low numbers are allowed in food
GROWTH REQUIREMENTS
* Temperature range
7 - 48 o C (optimum 37 oC)
* pH range
4 - 9.8 (optimum 6 - 7)
* Facultative anaerobe
REQUIREMENTS FOR TOXIN PRODUCTION
• Range is more limited than growth range
optimum temperature 40 – 45 o C
Aw above 0.85
Staphylococcal Exotoxin
(Enterotoxin / Neurotoxin)
* Resistant to proteolytic enzymes
e.g. trypsin in the gut
* Resistant to heat
Mechanism of Activity
• Toxin (exotoxin) is performed and ingested in
food
• Stimulates neural receptors in the
gastrointestinal tract
• Vomiting within approx 4 hours (1-6 hours) after
ingestion of toxin
• The toxin can also induce diarrhea, nausea,
headache
Examples of foods implicated in outbreaks
•
•
•
•
•
Salted meats
Cold cooked meats
Poultry
Custard
Cream filled bakery products
(whipped cream)
• Mayonnaise
• egg
PREVENTION
MOST OUTBREAK ASSOCIATED WITH ONE OR MORE OF :
• Inadequate in refrigeration
• Food prepared in advance
• Poor personal hygiene
• Moderate cooking or heat processing
• Holding food in warmer
SO…
* Control post-process contamination
* Control temperature abuse (cooking/ holding/ refrigeration)
* Handle food correctly
* Good quality raw material
Salmonella
TAXONOMY
•
•
•
•
Enterobacteriaceae
Gram Negative, Short Rod
Non spore forming
Peritrichous flagella
RESERVIOR
• Intestinal of domestic and wild animal
• Water, Sewage, Environment
GROWTH REQUIREMENTS
* Temperature range
optimum 37 oC
42 oC used for selective enrichment
* pH range
4-9
* Facultative anaerobe
Found in many foods :
• Contamination directly or indirectly with animal or human
feaces
- Raw/Undercooked eggs
- Uncooked meat
- Raw milk and milk products
- Poultry and poultry products
- Skim milk powder
- Ice-cream
- Mayonnaise
- Chocolate
- Cantaloupes
Clinical
•
•
•
•
•
Diarrhoea
Vomiting
Antibiotics minimal effect
Organism may be excreted for weeks
Some outbrakes have shown very low
infective dose causing death in infants,
elderly and immunosuppressed.
PREVENTION
• Correct food hygiene – direct or indirect
feacal contamination
• Correct food processing – heating /
cooling / storing.
• Correct personal hygiene to control
secondary spread
• Food handlers should have consecutive
negative feacal cultures before returning to
work with food.
Indicator Microorganisms
Coliform
• is the name of a test for the Enterobacteriaceae family.
• commonly-used bacterial indicator of sanitary quality of foods and
water.
• They are defined as rod-shaped Gram-negative non-spore forming
organisms.
• Some genus can ferment lactose with the production of acid and
gas when incubated at 35-37°C.
• abundant in the feces of warm-blooded animals, but can also be
found in the aquatic environment, in soil and on vegetation.
• they are easy to culture and their presence is used to indicate that
other pathogenic organisms of fecal origin may be present. Fecal
pathogens include bacteria, viruses,or protozoa and many
multicellular parasites
Escherichia coli
• Member of the coliform group
• Gram Negative, rod and Non-sporulating
• Facultative anaerobic
• ferment lactose at 44°C in the fecal
coliform test
• When cultured on an EMB plate,
a positive result for E. coli is Metallic
sheen colonies on a dark purple media.
Reference
Adams, M.R. and Moss, M.O., Food Microbiology,
2008

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