chapter 19

Question 1

food-borne pathogens

Answer 1

• Many diseases can be transmitted by means of foods. Any food that is handled, processed or stored improperly may be a public health hazard
  
  • Many fresh foods are contaminated with pathogens, but the initial population is usually too low to cause illness in a helathy individual. Ex: raw milk
  • The subsquent abuse of the food (ex; storage at warm temp.) permits the growth of pathogens to a level sufficient to cause illness
  • Food poisoning/intoxicatuon: caused by microbial toxins in food. Symptoms appearquickly
    Food infection: organisms are ingested woth the food and muliply in the host. Symptoms take longer to develop. Illness may be due to tissue invasion, production of toxins or both

Question 2

top 10 causes of food-borne diseases

Answer 2

1. Leaving cooked foods at room temp.
   
   2. Lapse of 12h or more between preparation and consumption
   3. Colonized/infected persons handling food
   4. Inadequate reheating
   5. Improper hot holding
   6. Contaminated raw food/ingredients
   7. Foods from unsafe sources
   8. Improper cleaning of equipment
   9. Cross contamination- raw to cooked
      Inadequate cooking

Question 3

3 most frequently reported diseases

Answer 3

Salmonellosis, campylobacter and giardiasis

Question 4

botulism

Answer 4

• Food poisoning, ingestion of the neurotoxin produced by Clostridium botulinum
  
  • 10% mortality, cause flaccid paralysis, respiratory or cardiac failure. Symptoms: difficulty swallowing, double vision, breathing difficulty, paralysis. 1-2 days
  • Anaerobe that produces spores, risk factors:
    1. Home canning, insufficient heat to kill the spores
    2. Processed foods that are not reheated (non-acid canned vegetables, sliced meats)
    3. Spores gerinate, growth, toxin is produced
• • toxin is destroyed by heating (80C, 10 min). Properly cooked foods are safe to eat; it destroys the toxin, not the organisms

Question 5

staphylococcal food poisoning

Answer 5

• Most common form of food poisoning, accounts for 40% of food poisoning cases
  
  • Due to enterotoxin (SE) produced by some strains of Staphylococcus aureus (enterotoxigenic strains). The toxin is relatively heat-stable (30 mun at 100C, 16h at 60C)
  • 20-30% of humans are colonized by S. aureus (skin and upper respiratory tract). It is easily transferred to food where it can grow and produce the toxin. Symptoms appera quickly (1-6h): nausea, vomiting, diarrhea
  • Associated with food prepared in large quantities and then, left at room temp. (banquet, picninc, airline meals). Halotolerant, can grow on salted sausage..
    Keep cold food col and hot food hot. Adequate sanitation/hygiene

Question 6

salmonella enterica

Answer 6

• More than 2000 serovars. (typhimurium, enteritidis, typhi). Only a fraction is isolated from human infections
  Infections of mammals, birds and reptiles
• Food infection, salmonella grows in the intestinal tract (salmonellosis); uses 2 injectisome systems. Most frequent serovars are enteritidis and typhimurium
  
  • 10^5-10^8 organisms are required to cause disease. SALMONELLA must usually multiply in the foods before the food is eaten
  • Symptoms are caused by the invasion and destruction of the intestinal epithelium
  • Associatied with uncooked or slightly cooked foods, or cooked foods that are contaminated after cooking (cross contamination)
    COOKING KILLS SALMONELLA ENTERICA. Good sanitation practices are important to minimize the chances of cross contamination

Question 7

e. coli

Answer 7

• Fecal coliforms BUT DOES NOT GROW AT 44.5; escape detection by standard fecal coliform methods
  
  • Enterohemorrhagic e. coli (EHEC). Effective dose is less than 100 microorganisms. COOKING KILLS the microorganisms
  • Toxin damage the underlying tissues = causes bloody diarrhea (hemorragic colitis)
    Toxin travels through the blood stream and destroys cells in the kidney = causes hemolytic uremic syndrome (HUS), can result in acute renal failure and death

Question 8

3 terms irradiation

Answer 8

• RADAPPERTIZATION: kill all microorganisms
  
  • RADICIDATION: kill specific microorgansisms
    RADURIZATION: reduce overall contamination

Question 9

Chemicals and other treatments

Answer 9

• NITRITE: prevents outgrow of C. botulinum
  
  • SULFITES: wine industry, inhibits wild yeasts
  • NISIN: bacteriocin produced by LACTOCOCCUS LACTIS
    1. Present in cheeses made with lactococcus lactis
    2. Effective against gram- positive organisms, including lactic acid bacteria (L. MONOCYTOGENES, S. AUREUS, B. CEREUS, C. BOTULINUM)
    BACTERIOPHAGES PREPARATION (FDA has approved a cocktail of bacteriophages against LISTERIA MONOCYTOGENES)

Question 10

cereulide

Answer 10

• Toxin produced by B. Cereus (spore-forming)
  
  • Attacks the mitochondrion, compromise membrane potential and oxidative phosphorylation
  • Eventually leads to cell death (apoptosis)
  • Acute emetic agent (causes vomiting)
    Especially toxic for liver and pancreas (beta cells)

Question 11

food processing/preservation

Answer 11

• Aims:
  
  1. Prevent or delay decomposition by microorganisms (spoilage)
  2. Destroys pathogens or inhibit their growth
  3. Prevent or delay self-decomposition by enzymes present in food
     - Refrigeration and freezing
     - Heating (pasteurization)
     - Canning
     - Reducing water availability
     - Irradiation
     chemicals

Question 12

refrigeration and freezing

Answer 12

• Aims: slow or inhibit growth of microorganisms
  
  • At -20C, the aw can reach 0.82. most microorganisms cannot grow
  • Viable microorganisms will resume growth once the temp. Is permissive
    Freeze/thaw cycles affects tje quality of the food (ice crystals) : can have growth of microorganisms between each cycle

Question 13

pasteurization

Answer 13

• Aim: reduce the number of microorganisms to delay spoilage and to eliminate pathogens
  
  • Dairy products, liquid egg products, alcoholic beverages, fruit juice
  • 3 methods for milk:
    1. Long temperature long time (LTLT): 30 min, 62.8C, bad taste (ice cream and cheese)
    2. High temperature short time (HTST): 15 sec, 71.7C (Milk for drinking)
    3. Ultahigh temperature (UHT): 2 sec, 141C (long shelf life at room temp., virtually sterile)
  *** LTLT OR HSLT TREATED MILK IS EQUALLY SAFE
  Time and temperature required are affected by the amount of fat, sugar and proteins