Food Intoxication Flashcards
FOOD BORNE INTOXICATIONS
These are diseases caused by consumption of food
containing:
- Biotoxicants, which are found in tissues of certain plants and animals.
- Metabolic products (toxins) formed and excreted by
microorganisms (such as bacteria, fungi, and algae), while they multiply in food or in gastrointestinal tract of man. - Poisonous substances, which may be intentionally or
unintentionally added to food during production, processing, transportation, or storage. - Food borne intoxications have short incubation periods (minutes to hours) and are characterized by lack of fever.
Food borne intoxications can be classified into:
a. Bacterial intoxications
b. Fungal intoxications
c. Chemical intoxication
d. Plant toxicants, and
e. Poisonous animals.
BACTERIAL FOOD BORNE INTOXICATIONS
- Staphylococcus aureus intoxication
- Bacillus cereus food borne intoxication
- Clostridium perfringens food borne intoxication
- Clostridium botulinum food borne intoxication
Staphylococcus aureus food borne intoxication
This is a type of food borne intoxication is caused by
consumption of food contaminated with staphylococcal enterotoxins produced by certain strains of Staphylococcus aureus while growing in food.
The organism produces the following five serologically different enterotoxins that are involved in food borne intoxication.
Growth conditions (Staphylococcus aureus)
•Staphylococcus aureus is a facultative anaerobe, non-
spore forming Gram positive cocci.
• It grows at a range temperature between 12-44oC
(optimum 37oC) and pH range 4.0-9.83 (optimum 7.4-7.6).
•Growth occurs in an environment containing up to 18% sodium chloride and water activity of 0.86 - 0.88 when growing aerobically and 0.9 under anaerobic conditions.
Toxin production (Staphylococcus aureus)
•Toxin production occurs at growth temperature 12-44oC, pH 4.2, and salt concentration of ≤10%.
•No toxin production occurs at temperatures below
12oC, pH < 4.2, and > 10 % salt.
Nature of enterotoxins (Staphylococcus aureus)
•All the staphylococcal enterotoxins are heat stable (withstand heating at 100oC for one hour) and ordinary
cooking procedures, pasteurization, and drying do not
inactivate these enterotoxins.
•They are insensitive to pH changes (pH stable) and
resistant to most proteolysis enzymes (trypsin, chymotrypsin, renin, and pepsin).
•The enterotoxins are also not affected by irradiation.
Competition with other organisms (Staphylococcus aureus)
•Staphylococcus aureus is a poor competitor and therefore grows poorly or not at all when growing together with other microorganisms.
•Majority of S. aureus food poisoning is due to foods in which the microbial flora is substantially reduced, such as cooked, cured, or pasteurized foods.
Vehicle foods (Staphylococcus aureus)
•Milk and milk products, including pasteurized milk, yogurt, chocolate milk, fermented milk, cream filled pastries, poultry, fish, shellfish, meat, and meat products, non meat salads, egg and egg products, vegetables, and cereal products have been involved.
Reservoirs (Staphylococcus aureus)
•Staphylococci are found in varying numbers in air, dust, water, food, feces, and sewage.
•The primary habitat of S. aureus is the mucous membranes of the nasopharynx and skin of man and
animals.
•The organism is found in the nose, skin, saliva, intestinal contents, and in feces.
•Contamination of foods may be traced to food handlers with minor septic hand infections or severe nasal infections
•The nasal mucous membrane is another particularly
important source of staphylococci of human origin.
Disease symptoms in man (Staphylococcus aureus)
• Incubation period is 1-6 hrs after consumption of food
contaminated with at least 1.0 µg of enterotoxin.
•Clinical signs include salvation, nausea, vomiting, abdominal cramps, sometimes diarrhea with prostration.
• It has an attack rate of 5-100%, but fatalities, which occurs in children, the old and debilitated victims are rare.
•Duration of illness is 24-72 hrs.
•Dose of 1.0 µg or more is needed to cause disease.
Bacillus cereus food borne intoxication
•This is a food borne intoxication caused by consumption of enterotoxins produced by some strains of Bacillus cereus.
•The organism produces the following enterotoxins, which are involved in a food borne intoxication;
a. Two diarrhoeal enterotoxins: -hemolysin BL enterotoxin, non-hemolytic enterotoxin
b. Emetic toxin
Vehicle foods (Bacillus cereus)
•Bacillus cereus is a common soil saprophyte and is easily spread to many types of foods, especially of plant origin,
• It is frequently isolated from meat, eggs, and dairy products,
•Cereal dishes e.g. rice, spice, mashed potatoes, herbs,
vegetables, minced meat, cream, and milk pudding have been involved in B. cereus poisoning.
Emetic syndrome (Bacillus Cereus)
•The syndrome is characterized by nausea, vomiting,
abdominal cramps and sometimes diarrhea that occur 1-6 hrs after consumption of contaminated food. The syndrome is associated with ingestion of rice and pasta based foods.
Diarrhea syndrome (Bacillus Cereus)
• In the diarrhea syndrome, patients experience profuse diarrhea (watery stool), abdominal cramps, and tenesmus (rarely vomiting) beginning 8 to 16 hours after ingestion of contaminated food.
•Fever is absent, and symptoms resolve within
approximately 12 hours.
