Foodborne diseases Food poisoning

Food poisoning:
Gastrointestinal illness caused by
consumption of food contaminated with
bacteria, fungi, parasites, viruses, bacterial or
fungal toxins or chemicals.
• In 2010, Public health workers (Foodborne
diseases active surveillance Network
(Food-Net)) estimate approx. 1000
outbreaks, 48 million illnesses, 128,000
hospitalization, and 3000 deaths annually
due to foodborne illness in USA.
Foodborne disease outbreak:
Gastrointestinal illness of two or more
persons who experience similar symptoms
due to ingestion of contaminated food or
water confirmed by epidemiological analysis
Types of Food Poisoning:
• Intoxication.
• Food poisoning caused by microbial entry.
Food poisoning caused by microbial entry:
• Due to ingestion of food contaminated by
microbes or microbes and their toxins.
• Caused by Vibrio species, ETEC, EPEC,
Salmonella, Campylobacter, and others.
• This type is mainly characterized by
longer incubation period than intoxication,
fever, and lower gastrointestinal
Food poisoning Due to intoxication
Ingestion of food contaminated by microbial
Intoxication is mainly characterized by short
incubation period, upper gastrointestinal
symptoms such as nausea and vomiting.
Caused by:
o Staphylococcus aureus,
o Clostridium perfringens,
o Clostridium botulinum,
o Bacillus cereus.
Staphylococcus aureus toxigenic disease:
Implicated food:
Carbohydrate rich food: cake, pasta, potato,
Protein rich food: beef or pork-meat,
mayonnaise, milk and its products (e.g. icecream).
Source of food contamination:
Usually a carrier persons such as foodhandlers. The organism grows in the food and
produces the toxin.
Incubation period: Very short (1 – 6 hours;
epidemiological clue)
Symptoms: Vomiting, nausea, abdominal
cramps, followed by diarrhea but no fever.
Abdominal pain and inflammation are absent.
Duration of illness: 24 – 48 hrs (self limited).
Types of enterotoxins produced by S. aureus:
• Enterotoxins: A, B, C, D, E, and G.
• Enterotoxin: F & pyrogenic exotoxin c.
Enterotoxins: A, B, C, D, E, and G.
o Produced by 65% of Staphylococcus aureus.
o Heat-stable (resist ~30 minutes of boiling 100ᵒC).
o Resistant to hydrolysis by gastric proteases.
o Do not change the food taste, color, or odor.
o Enterotoxin A is the most common. Enterotoxin C
and D are associated with contaminated milk.
o These toxins may cause Watery diarrhea;
o Enterotoxin B is associated with Staphylococcus
pseudomembrance enterocolitis.
Enterotoxin F and pyrogenic exotoxin c:
(Toxic-Shock Syndrome toxin-1):
Mainly produced during S. aureus growth in
the GIT. When reached bloodstream, these
toxins will cause sepsis, septic shock, and
multiple organ distress syndrome (MODS).
• Clinical: symptoms, history of eating meats
of high salt content or eating high sugar
content food.
• Laboratory Diagnosis:
Laboratory Diagnosis:
o Specimens:
Swabs from vomitus and implicated food.
Skin of food-handler, Nasal swabs of carriers.
o Phage typing and biotyping: to confirm the source of
the bacteria.
Bacillus cereus intoxication:
Two presentations: Emetic syndrome or Diarrheal
 Emetic syndrome: Heat-stable enterotoxins.
-Associated foods: Consumption of toxin in
boiled or fried rice and carbohydrates rich food*.
-Incubation period: Short incubation period of
1-6 hours
-Clinical presentation: Upper gastrointestinal
symptoms such as nausea, vomiting and abdominal
-Duration of illness: 6-10 hour.
 Diarrheal syndrome: Heat-Labile enterotoxins.
- (Stimulate adenylate cyclase-cAMP system).
- Associated foods: consumption of contaminated
meat products, soups, sauces, and vegetables.
- Incubation period: Longer incubation period of
8-16 hours.
- Symptoms and signs: Watery diarrhea,
abdominal cramps and occasional nausea &
-Duration of illness: 24-48 hours.
-Isolation of microbes from clinical specimens and
food samples(same species identification).
-Phage typing and biotyping.
Clostridium perfringens intoxication:
Implicated food:
-Poultry, meat, pork-meat.
-Spores are present in cooked-meat that not is
refrigerated; spore will germinate due to exposure to
gastric acid and produce it’s toxins.
Types of Toxins: Enterotoxin & exotoxin.
Enterotoxin: Heat-labile: with maximal activity in
ileum. Inhibits glucose and ions transport; damage of
intestinal epithelial cells and loss of protein.
-Effect: Watery diarrhea without nausea or
Exotoxins: Alpha-toxin ; lecithinase: Heatstable toxin.
Disease: Enteritis necroticans: Intestinal
necrosis with bloody diarrhea (only the toxin,
the bacteria is not present)
Damage of phospholipids in the cell
membrane causing lysis of RBCs ,WBCs,
platelets, and endothelial cells.
If the toxin reach the bloodstream; sepsis and
septic shock; Mortality rate: 40%.
Diagnosis of Clostridium perfringens
• Watery diarrhea:
-Positive culture from stool specimens and
implicated food samples; 105 CFU/gm is a
diagnostic feature.
-The enterotoxin can be detected in stool, and antitoxin antibodies can be detected in patient serum.
• Enteritis necroticans:
-Negative stool culture. Antibodies can be detected
in serum in 65-85% of patients.
Clostridium botulinum intoxication: Botulism:
o Implicated food:
Canned food, sausage, canned salmon and salted fish.
o Produced Toxin: Botulinum toxin A,B,C,….G.
 Polypeptide, heat-labile (10 minutes at 60 ᵒC).
 Has two subunits:
light-A chain: Neurotoxin*.
heavy-B chain: protects the toxin from stomach
acidity. The toxin is also protected from gastric
enzyme by large content of protein in the meal.
o Incubation period: 12-72 hours.
Effect of botulinum toxin:
Effect of botulinum toxin:
After absorption, circulating neurotoxins affect the
cholinergic nerves function:
 Effect on sympathetic nervous system:
Blocking of excitatory acetylcholine release in
neuromuscular junctions; bilateral descending
flaccid paralysis.
 Effect on parasympathetic nervous system:
Respiratory paralysis; death.
 Effect on cranial nerve function: blurred vision,
fixed dilated pupils.
-Adequate ventilation support.
-Gastric Lavage and Penicillin therapy.
-Trivalent botulinum antitoxin vaccination.
- With good care the mortality rate is decreased to
-Good heating of food to destroy toxin.
-Storage of food at 4C.
Fungal Intoxication: Mycotoxicosis:
Toxins: Aflatoxins, ergot alkaloids, tricothecene &
 AflatoxinsB1,B2, G1,G2:
-Produced by Aspergillus flavus.
-Implicated food: Peanuts, Corn, grains.
-Effect: liver necrosis, hepatocarcinogen.
 Ergot alkaloids:
-Produced by Claviceps purpurea.
-Implicated food: wheat, corn, rice.
-Effect: Arterial and venous vasoconstriction and
endothelial cell damage. (ergotamine drug)*
 Tricothecene:*
-Produced by Fusarium species.
-Implicated food: corn, rice, wheat.
-Effect: inhibition of DNA replication and mRNA
transcription in the epithelial lining of GIT and
bone marrow (diarrhea, hypotension, weakness,
bleeding and death)
 Ochratoxins A,B,C:
-Produced by Aspergillus species.
-Food: Corn, rice.
-Effect: Destruction of proximal tubules of
kidney; decreased electrolytes absorption, increased
water excretion.

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