Food-Borne Pathogens

Question 1

Botulism

Answer 1

• Caused by Clostridium botulinum
• AB-type neurotoxin
• causes flaccid paralysis, respiratory or cardiac failure
• Toxin destroyed by cooking but spores are not

Question 2

Staphylococcus aureus

Answer 2

• Most common form of food poisoning
• Due to an enterotoxin
• Symptoms: nausea, vomiting, diarrhea
• Associated with food prepared in large quantities and left at room T°
• Heat stable

Question 3

Salmonella enterica

Answer 3

• Infection of mammals, birds & reptiles
• Grows in the intestinal tract
• Uses two injectisome systems
• Associated with uncooked or slightly cooked foods, or cooked foods that are contaminated after cooking
• Killed by cooking

Question 4

Escherichia coli O157:H7

Answer 4

• infects the intestinal mucosa
• Produces AB-type toxin that inhibits protein synthesis
• kills intestinal cells, which produce inflammation and diarrhea.
• Toxin may get into the
  bloodstream and kidney cells and lead to hemolytic uremic syndrome.
• can result in acute renal failure and death
• Cooking kills the microorganism

Question 5

Food processing/preservation: Aims

Answer 5

• Prevent or delay decomposition by microorganisms (spoilage)
• Destroy pathogens or inhibit their growth
• Prevent or delay self-decomposition by enzymes present in the food

Question 6

Food processing/preservation: Methods

Answer 6

• Refrigeration and freezing
• Heating (pasteurization)
• Canning
• Reducing water availability
• Irradiation
• Chemicals

Question 7

Refridgeration and freezing: Aim

Answer 7

slow or inhibit growth of microorganisms

Question 8

Pasteurization: Aim

Answer 8

Reduce the number of microorganisms to delay spoilage and to eliminate pathogens

Question 9

Pasteurisation: Methods

Answer 9

Low temperature long time (LTLT):
* 30 min, 62.8°C, bad taste (ice cream & cheese)

High temperature short time (HTST):
* 15 sec, 71.7°C (milk for drinking)

Ultrahigh temperature (UHT):
* 2 sec, 141°C

Question 10

Canning: Aim

Answer 10

• Seal the food from the outside world and heat the container to kill most, if not all, of the microorganisms.
• Creates an anaerobic environment

Question 11

Canning: Temperatures

Answer 11

• 100°C for acidic food
• Up to 121°C for low-acid food

Question 12

Canning: 12D process

Answer 12

Temperature and time of exposure must be sufficient to kill 10 12 spores of Clostridium botulinum

Question 13

Water availability: Aim

Answer 13

• Prevent microorganisms from growing
• Doesnt necessarily kill the microorganisms but inhibits their growth

Question 14

Water availability: Methods

Answer 14

• Drying
• Adding salt or sugar

Question 15

Irradiation: Aim

Answer 15

Aim:
* reduce contamination of fresh
product by pathogen and spoilage
organism

Question 16

Irradiation: Doses

Answer 16

• Kill all microorganisms (radappertization)
• Kill specific microorganisms (radicidation)
• Reduce overall contamination (radurization)

Question 17

Chemicals: Aims

Answer 17

Aim:
* control the growth of microorganisms (usually selected microorganisms)

Question 18

Chemicals recognised as safe

Answer 18

• Nitrite: prevents outgrowth of C. botulinum.
• Sulfites: wine industry, inhibits wild yeasts.
• Nisin: bacteriocin produced by Lactococcus lactis