Food Intoxication

Question 1

FOOD BORNE INTOXICATIONS

Answer 1

These are diseases caused by consumption of food
containing:

1. Biotoxicants, which are found in tissues of certain plants and animals.
2. 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.
3. Poisonous substances, which may be intentionally or
   unintentionally added to food during production, processing, transportation, or storage.
4. Food borne intoxications have short incubation periods (minutes to hours) and are characterized by lack of fever.

Question 2

Food borne intoxications can be classified into:

Answer 2

a. Bacterial intoxications
b. Fungal intoxications
c. Chemical intoxication
d. Plant toxicants, and
e. Poisonous animals.

Question 3

BACTERIAL FOOD BORNE INTOXICATIONS

Answer 3

1. Staphylococcus aureus intoxication
2. Bacillus cereus food borne intoxication
3. Clostridium perfringens food borne intoxication
4. Clostridium botulinum food borne intoxication

Question 4

Staphylococcus aureus food borne intoxication

Answer 4

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.

Question 5

Growth conditions (Staphylococcus aureus)

Answer 5

•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.

Question 6

Toxin production (Staphylococcus aureus)

Answer 6

•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.

Question 7

Nature of enterotoxins (Staphylococcus aureus)

Answer 7

•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.

Question 8

Competition with other organisms (Staphylococcus aureus)

Answer 8

•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.

Question 9

Vehicle foods (Staphylococcus aureus)

Answer 9

•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.

Question 10

Reservoirs (Staphylococcus aureus)

Answer 10

•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.

Question 11

Disease symptoms in man (Staphylococcus aureus)

Answer 11

• 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.

Question 12

Bacillus cereus food borne intoxication

Answer 12

•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

Question 13

Vehicle foods (Bacillus cereus)

Answer 13

•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.

Question 14

Emetic syndrome (Bacillus Cereus)

Answer 14

•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.

Question 15

Diarrhea syndrome (Bacillus Cereus)

Answer 15

• 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.

Question 16

Clostridium perfringens intoxication

Answer 16

1. This is a food borne intoxication caused by Clostridium perfringens enterotoxin (CPE) produced in the gastrointestinal tract by enterotoxigenic strains of C. perfringens.
2. The organism is found in the soil, dust, water, sewage marine sediments, decaying materials, intestinal tracts of humans and other animals.
3. This organism is a spore-forming, anaerobic, Gram-positive bacillus.
4. Spores produced by these organisms can resist boiling for 4 or more hours.
5. If the spores are present as contaminants on raw meat, they may resist boiling or steaming, and on slow cooling, the spores will germinate into rapidly multiplying bacterial cells, which produce large amounts of toxin.

Question 17

Cause of intoxication (Clostridium perfringens)

Answer 17

•Clostridium food borne intoxication is caused by the
ingestion of food containing large numbers of vegetative cells of enterotoxigenic C. perfringens type A and some type C and D strains.

•These cells multiply in the intestine and sporulate, releasing Clostridium perfringens enterotoxin (CPE).

•Sometimes CPE may be pre-formed in food, and once the food is consumed, symptoms may occur within 1-2 hours.

Question 18

Characteristics of CPE

Answer 18

• Clostridium perfringens enterotoxin (CPE) is synthesized during sporulation.

• CPE is heat labile (destroyed at 60oC for 10 min), and its activity is enhanced by trypsin.

• Note: The food poisoning strains are heat resistant and survive heating at 100oC for 1 hr).

Question 19

Vehicle foods (Clostridium perfringens)

Answer 19

•The food involved are those that are prepared one day and served the next day.

•Foods that have been involved include red meats, chickens, fish, pork, fruits, vegetables, spices, etc.

•The heating of such foods is inadequate to destroy heat- resistant endospores,

•Upon cooling and warming the endospores germinate and grow.

•Cooking kills the vegetables cells of Cl. perfringensbut activates surviving spores, which will germinate and multiply.

•Foods poisoning occurs when the level reaches 107-108 cells/g of food,

•Growth is enhanced by anaerobic conditions achieved after removal of oxygen by cooking.

Question 20

Mode of transmission to foods (Clostridium perfringens)

Answer 20

1. Directly from slaughter animals
2. Contamination of slaughter meat from containers, handlers, dust, and water.
3. Cross -contamination in the kitchen environment.

Question 21

Symptoms of disease in man (Clostridium perfringens)

Answer 21

•Symptoms appear 6-24 hours after ingestion of a large number of viable vegetative cells up to 5x108/g food, but not after ingestion of spores.

•Symptoms include nausea, intestinal cramps, pronounced diarrhea

• Vomiting is rare, and the illness takes a duration of 1-2 days.

Question 22

Clostridium botulinum foodborne Intoxication

Answer 22

•Clostridium botulinum food borne intoxication (botulism) is a type of food poisoning caused by consumption of enterotoxins produced by strains of Clostridium botulinum.

•C. botulinum is an obligate, spore-forming anaerobe, and Gram-positive bacilli

•The strains are divided into proteolytic and non-proteolytic types according to whether they hydrolyze proteins or not.

Question 23

Growth characteristics (C. Botulinum)

Answer 23

•Proteolytic strains grow at temperature range between 10-50oC, while non-proteolytic grows at 3.3-45oC (optimum 35-37oC).

•Toxin production occurs at temperature range between 25-30oC.

•Both strains grow at minimum pH of 4.5.

•Proteolytic strains produce an active botulinal toxin, while non-proteolyic strains produce inactive pro-toxin that requires activation by trypsin.

Question 24

Characteristic of Botulinal toxins

Answer 24

•These toxins are neurotoxins that are highly toxic, heat labile (inactivated by heating at 80oc for 10 min), unstable at alkaline pH (but stable below pH 7.0).

•The toxins can resist the action of the gastric and intestinal juices.

•Botulinus toxin is one of the most lethal poisons known. The calculated lethal dose for an adult person is 10 µg.

Question 25

Types of foods implicated (C. Botulinum)

Answer 25

•Foods associated with anaerobic conditions such as spoiled canned meat, or hams and bacon stacked without air access, are particularly liable to be infective. •Uncooked fresh foods are safe because they are eaten before the toxin has had time to develop, while if foods are cooked (>80oC, >5mins), the toxin is destroyed.

Question 26

Role of preservatives in meat

Answer 26

•Nirates/nitrites are used in canned meat as preservatives. The salts reduce the chances of growth of C. botulinun and inhibit toxin production. •The danger of botulism has been the deciding factor in the formulation of food processing techniques, especially canned meat .

Question 27

Mode of transmission (C. Botulinum)

Answer 27

1. Contamination of food due to improper handling. 2. Insufficient heating of food to destroy spores. 3. Spores present in animal tissues, e.g. meat and fish.

Question 28

Adult botulism

Answer 28

•The period of incubation in man is usually 12-72 hrs). •Symptoms include nausea, vomiting, fatigue, dizziness, headache, dryness of skin, mouth and throat, constipation, lack of fever, nerve paralysis and great muscular weakness, double vision, respiratory failure and death. •Duration of illness 1-10 days and mortality is high up to 60-100% of affected persons. The earlier the appearance of symptoms, the higher the mortality rate.

Question 29

Infant botulism

Answer 29

•Occurs in infants less than 1 year of age following ingestion of spores in honey and syrup. •The spores germinate in the gastrointestinal tract with toxin production. • A high number of spores are found in feces of infants during acute phase of the disease. The number reduces as recovery progress. •Symptoms are similar to adult botulism

Question 30

Animals biotoxications

Answer 30

•This type of intoxication occurs as a result of consumption of poisonous animals. •Animal tissues may be rendered poisonous by bacterial and enzymatic decomposition, but some are naturally toxic. •Primary toxicity occurs due to inherent toxicants that arise due to normal metabolic processes.

Question 31

Ciguatera poisoning (ciguatoxicity)

Answer 31

1) Almost all fishes involved in ciguatera poisoning are reef or shore species that become toxic by feeding upon herbivores fish, which in turn feed on toxic algae or other toxophoric matter present in coral reefs or from related areas. 2) Over 400 species of fishes involved, including sharks, eels, jacks, and groupers. 3) The illness is caused by a heat stable ciguatoxin. 4) Symptoms include mild paralysis and gastrointestinal disturbances.

Question 32

Tetrodotoxin poisoning

Answer 32

•This type of poisoning is associated with puffer fish, mainly of the genus fugu from the Pacific, Atlantic, and Indian oceans. •Puffers contain tetrodotoxin, the most lethal poison from fish that can kill 60-70 % of human victims. •The toxin is heat stable, concentrates in the liver, and gonads of puffer fish. •One must ensure that the toxic organs are removed before the fish is eaten.

Question 33

Scombroid toxicity

Answer 33

•This type of poisoning involves consumption of tuna, bonitos, mackerel, and related fish, which become toxic due to bacterial decomposition arising from improper preservation. •The toxic principle is the heat stable histamine or histamine-like substances, e.g. saurine.

Question 34

Scombroid toxicity symptoms

Answer 34

•Symptoms of this type of poisoning resemble those of allergy. • Initially, there is a sharp or peppery taste, followed by headache, dizziness, abdominal pain, burning of throat, difficulty in swallowing, thirst, and gastrointestinal upsets. •A severe urticaria eruption may develop covering the entire body, which may be accompanied by severe itching. •Death may occur due to suffocation and shock. However, the acute symptoms are generally transient, rarely lasting more than 12 hours. •Treatment involves use of anti-histamines, which give effective relief. •Control of illness is through hygienic handling of fish to prevent bacterial decomposition.

Question 35

Mollusca

Answer 35

•Mollusca may either be inherently or secondarily toxic. Poisoning is mainly due to the transvectionof dinoflagellate protozoa toxins by the mollusca. •Mollusca are however not harmed by ingestion of dinoflagellates. Involved toxins are stored in the digestive glands, gills, and siphore from where they poison vertebrates •Mollusca involved are oysters, mussels,, and clams, which feed on dinoflagellates and planktons containing alkaloids making them toxic.

Question 36

Paralytic shellfish poisoning

Answer 36

•This results from consumption of shellfish such as oysters, mussels, and clams that have become toxic after consumption of toxic dinoflagellate protozoa, which pre-dominantly feed on planktons containing saxitoxin and accumulating the toxin in their tissues. •Saxitoxin is heat stable and highly toxic.The toxin acts by blocking the propagation of nerve impulses without depolarization. Small doses lead to tingling of mouth and lips, while higher doses lead to paralysis, collapse, and death. Mortality is about 1-22 %. There is no known antidote.

Question 37

Prevention of Paralytic shell fish poisoning

Answer 37

1. Avoiding sea foods from waters laden with toxic dinoflagellates. 2. Reduce toxin activity by heating above 100oC. Thorough cooking may reduce 70 % of the toxin activity in mussels.