Foodborne illnesses - gram+ pathogens

Question 1

What are the five gram-positive pathogens?

Answer 1

1. Listeria monocytogenes
2. Staphylococcus aureus
3. Bacillus cereus
4. Clostridium botulinum & perfringens

Question 2

Why is the prevention of contamination with L. mono important?

Answer 2

The mortality rate is 20%. Which is the case in the severe form of the disease, this form also van have an incubation time of three months, which makes it almost impossible to trace the origin. This is also the only pathogen that can potentially outgrow in the fridge (Tmin = 0 degrees) and in vacuum/MAP (fac. anaerobe).

Question 3

What are the symptoms of listeriosis? Also give inc. time

Answer 3

Mild listeriosis:
- Gastroenteritis, mild flu-linke
- Incubation time: 4-48 h
Severe illness:
- Stillbirth, septicemia (blood poisoning), meningitis (hersenvliesontsteking)
- Incubation time: 3h - 3 months

Question 4

What type of foods is L. mono mostly found?

Answer 4

Foods that are stored for a long time at a rather low temperature (Tmin = 0 degrees and relatively low pH)
Examples:
- Deli meat
- Soft cheese
- Raw milk
- Pate
- Smoked and lightly processed fish
- RTE foods

Question 5

What are different processing and storage methods to restrict outgrowth?

Answer 5

1. Fermentation –> reduce pH
2. Drying –> awmin =0.92
3. Heat the product –> D71.7 is 1-2s, therefore pasteurization will suffice

Question 6

Many people are Staphylococcus aureus carriers, however this rarely leads to outgrowth, how is that possible?

Answer 6

S. aureus is a very bad competitor.

Question 7

What are the symptoms of S. aureus intoxication, and how much of the toxin is needed for causing illness?

Answer 7

Mild symptoms, vomiting
- Inc. time: 0.5 - 6 hours
- Duration 1 - 2 days
- Either 10^6 CFU/gram or micro- to nanograms

Question 8

What kind of food products are S. aureus mostly present?

Answer 8

Protein rich foods with little competition.
- Heated foods which are recontaminated
- Salted meats (awmin = 0.83)
Interestingly low in milk, because there is a lot of competition. However, temperature abuse can lead to problems (if other MO are inactivated)

Question 9

Give six spore forming bacteria (food spoilage, food pathogens and non-food related pathogens)

Answer 9

Spoilage:
- B. subtilis
Foodborne pathogens:
- B. cereus
- Cl. perfingens & Cl. botulinum
Non-food related pathogens:
- B. anthracis
- B. thuringiensis (insecticide)

Question 10

Bacillus cereus is a toxin producer, which has two types. Give both types and their symptoms.

Answer 10

1. Emetic type:
   - Cereulide produced in carb-rich food products (that are cooled down slowly –> bulk rice)
   - mild-symptoms: vomiting (like S. aureus)
   - inc. time: 0.5-5h
   - duration: 6-24h
2. Diarrhoeal type:
   - Produced in the gut
   - Sauces, dessert, dairy, meat products
   - Mild symptoms: like Cl. perfringens
   - Inc. time: 8-16h
   - Duration: 12-24h