1. Food Biotechnology Dr. Tarek Elbashiti
Microbial Food-Borne Diseases 3

2. TYPES OF TOXINS Bacterial toxin Mold toxins
Staphylococcal intoxication (enterotoxin)
Botulism (neurotoxin)
Mold toxins
Mycotoxin (mycotoxisis)

3. Types of microbial food-borne diseases
Intoxication
illness occurs as a consequence of ingestion of a preformed bacterial or mold toxin (mycotoxin) due to its growth in a food.
A toxin has to be present in the contaminated food in an active form.
Once the microorganisms have grown and produced toxin in the food, there is no need of viable cells during the consumption of the food for illness to occur.
Eg. Staphylococcal food poisoning.

4. Infection
Illness results from consumption of food and water contaminated with entero-pathogenic bacteria or viruses.
It is necessary for entero-pathogenic bacteria and viruses to remain alive in the food or water during consumption.
Viable cells present in small numbers have the potential to establish and multiply in the digestive tract to cause the illness.
Eg. Salmonellosis, Hepatitis A.

5. Toxico-infection
Illness results from ingestion of a large number of viable cells of some pathogenic bacteria through contaminated food and water.
The bacterial cells either sporulate or die and release toxin(s) to produce the symptoms.
Eg. Clostridium perifringens gastroenteritis

6. Food intoxications
Toxin is produced by a pathogen while growing in a food.
Toxin can be heat labile or heat stable.
Ingestion of a food containing active toxin, not viable microbial cells, is necessary for poisoning.
Symptoms generally occur quickly, as early as 30 min after ingestions
Symptoms differ with type of toxin:
Enterotoxins produce gastric symptoms.
Neurotoxins produce neurological symptoms

7. Staphylococcus aureus
Organism
Gram positive cocci
Occur generally in grape like clusters
Are nonmotile, noncapsular and nonsporulating

8. Growth
Are facultative anaerobes but grow rapidly under aerobic conditions.
Cells are killed at 66°C in 12 min and at 72°C in 15s.
They are mesophiles with a growth range between 7-48°C and a rapid growth between 20-37°C.
They can ferment CHOs and also cause proteolysis by the extracellular proteolytic enzymes.
Grows well at low Aw (0.86), low pH (4.8) and high salt and sugar concentrations at 15% and in the presence of NO2.
Able to grow under several adverse conditions, S. aureus can grow in many foods.
Poor competitors in the presence of many other microorganisms in foods.
Enterotoxin-producing S. aureus strains associated with staphylococcal food intoxication.

9. Habitat
S. aureus naturally present in the nose, throat, skin and hair (feathers) of healthy humans, animals and birds.
Can be present in infections such as cuts in the skin and abscesses in humans, animals and birds, cuts in hands and facial erupted acne in humans.

10. Toxin and toxin production
6 enterotoxins are produced by enterotoxigenic strains:- A, B, C1, C2, D and E.
The toxins vary in heat stability
Normal temp and time used in processing or conventional heating will not destroy the potency of the toxins.
Rate of toxin production by a strain is directly related to its rate of growth and cell conc.
Optimum growth occurs around 37-40°C.
Staphylococcal toxins are enteric toxins and cause gasteroenteritis.

11. Disease and symptoms
 Symptoms occur within 2-4h with a range of 30min-8h and are directly related to the potency and the amounts of toxin ingested and an individuals resistance.
- Primary symptoms - salivation, nausea, & vomiting, abdominal cramps & diarrhea
- Secondary symptoms - sweating, chills, headache & dehydration

12. Botulism
Results in consumption of food containing toxin of Clostridium botulinum.
Is a Neurotoxin and produces neurological symptoms along with some gastric symptoms
Infant botulism occurs from the ingestion by the infant of C. botulinum spores that germinate, grow and produce toxins in the GI tract and cause specific symptoms.

13. Organism Cells are gram positive rods
Occur as single cells or in small chains, many are motile
Obligate anaerobes and form single terminal spores
Cells are sensitive to low pH (<4.6) , low Aw, moderate high salt(5.5%).
Spores do not germinate in presence of nitrate (250ppm).
Spores are highly resistant to heat (killed at 115°C).
Cells are killed at moderate temp (pasteurization).
Strains are proteolytic and nonproteolytic.

14. Growth Strains (type of toxin production) divided into 8 types A-H
A, B, E and F - associated with human food-borne intoxications
A- proteolytic, E-nonproteolytic
B & F either proteolytic or nonproteolytic.
Proteolytic strains - grow b/w 10°C and about 48°C with optimum temp of 35°C
Nonproteolytic strains - grow in the range of °C, optimum at 30°C
For growth - anaerobic condition

15. Habitat
Spores of C. botulinum are widely distributed in soil, sewage, mud, sediments of marshes, lakes and coastal waters, plants, and intestinal contents of animals and fishes.
Fruits and vegetables can be contaminated with spores from soil.
Fishes from water and sediments
Types A and B spores are more prevalent in soil, sewage and fecal matters of animals
Type E spores are generally found in marine environment.

16. Toxins and disease and symptoms
Toxins are neurotoxic proteins
For food intoxication in humans - Type A, B, E and F - extremely potent
Following ingestion
Toxins absorbed through intestinal wall, spread to the nerves and they block the transmission of impulse.
At initial stage (12-36h, but can be 2h) some GI disorders (nausea, vomiting, diarrhea and constipation) may be evident.
Neorological symptoms develop within a short time, esp if amount consumed is high.

17. Highly potent toxins-(1ng/kg body weight) is necessary for severe symptoms and even death.
Neurological symptoms include difficulty in breathing, speaking, dryness of mouth, paralyses in all involuntary muscles that spreads to the diaphragm, lungs and heart.
Death usually results from respiratory failure.
Toxins are antigenic (contains antigen) - thus antitoxins are present

18. Botulism Poisoning Source of trouble:
Low acid foods that were improper canned
Trouble signs
Clear liquid turn milky
Cracked jars
Loose or dented lids
Swollen or dented cans
An off odor

19. Prevention
Examine all canned foods before cooking
Cook & reheat foods thoroughly
Keep cooked food hot above 140 degrees or cold below 40 degrees.
Symptoms after eating
Double vision and droopy eyelids
Trouble speaking, swallowing or breathing
Untreated botulism can be fatal.

20. MYCOTOXICOSIS Organism
Toxigenic species and strains of molds from many genera are known to produce mycotoxins
Some toxigenic strains from several species and genera and the toxin they produce include:
- Asp. flavus (alfatoxin)
- Asp. parasiticus (alfatoxin)
- Asp. nidulans (sterigmatocystin)
- Penicillium viridicatum (ochratoxin)
- Pen. patulum (patulin)
- Pen. roqueforti (roquefortin)
The toxigenic strains cannot be differentiated from nontoxigenic strains.

21. Growth Molds grow best in humid and warm environments.
They are aerobic and thus need air for growth
they can grow slowly at very low Aw (0.65), low temperature (refrigerated temp) and low pH (3.5)
These conditions are often used to extend the shelf life of many foods.
Unless vacuum packaging is used, molds can grow in foods and if toxigenic can produce toxins in foods.

22. Habitat Spores are present in - Soil - Dust - environment
Many foods have viable spores or mycelia especially before heat treatment.

23. Toxin and toxin production
Mycotoxins include a large numbers of toxins produced by different toxigenic species and strains of molds.
Are small molecular hetrocyclic organic compounds and have more than one chemicial type. E.g aflatoxin (B1 and G1).
Produced by the toxigenic mold strains as secondary metabolites.
Toxin production in general is directly related to the growth rate of a mold strain

24. Food association
Consumption of mycotoxin-contaminated food can cause mycotoxicosis in humans.
Feeding moldy products to food animals and birds can also produce foods of animal origin (milk , eggs) that are contaminated with mycotoxins.
Many of the mycotoxins are resistant to heat used in the normal preparation of foods.

25. Prevention of mycotoxicosis
Contamination of food with toxigenic mold strains (or all molds) should be reduced.
Proper packaging should be used to reduce the incidence.
Heat treatment where applicable reduce load by killing molds and their spores.
Preventing growth in food and in feeds.
Use anaerobic packaging.

26. Reduce Aw where possible to ≤ 0.6
Freezing
Using specific preservatives against mold growth.
Chemical treatments-ammonia, hydrogen peroxide and sodium hypochlorite inactivates alfatoxins.
Trimming -not a good methods as the remaining portion may have some mycotoxins.