Lecture 13: Food Poisoning Flashcards
List food hazards in order of concern by regulatory agencies (FDA, CDC)
- Microbial
- Nutritional
- Environmental
- Natural toxicants
- Pesticide residues
- Food additives
Which microorganisms can only multiple in food?
Yeasts and molds
Which microorganism can multiply in food and humans?
Bacteria
Which microorganism can only multiply in humans?
Human viruses
Which microorganism multiplies in bacteria?
Bacterial viruses
Name the 2 general types of food-borne illness
Intoxications and infections
Food-borne intoxication
- aka food poisoning
- Relatively acute illness associated with the consumption of PRE-FORMED microbial toxins in food
- Microorganism must grow in the food, but not necessarily in consumer
Under the best conditions, a bacterial cell can divide every ____?
20-30 mins
Name the 3 food-borne intoxications we learned about in class
- Staphylococcus aureus
- Clostridium botulinum
- Bacillus cereus
How does one get staphylococcal intoxication?
Ingestion of a pre-formed enterotoxin (stomach toxin) from a Staphyloccocus species
What are the symptoms of staphylococcal intoxication?
- Salivation
- Nausea & vomitting
- Retching
- Abdominal cramps
- Diarrhea
Staphylococcal etiology: What makes it a problem?
- Ubiquitous in the environment
- Can grow in nasal and pharyngeal area of humans
- In CA, 50% of humans are carriers
Manifestations of staphylococcal intoxication
- Sudden onset = 1-6 hrs
- Short duration = 2-24 hrs
- Usually attributed to other causes (one-day flu)
- Fatalities are rare
What are the conditions under which staphylococcal toxin are produced?
- 50-140 F
- Rapid growth at 70-105 F
- Aerobic conditions (desires oxygen to grow)
What kinds of foods are high incidence for staphylococcal poisonings?
- Custard-filled bakery products
- Sliced cooked meats
- Chicken calad
- Cheeses
- Sausages
- Spray-dried milk
Staphylococcal prevention
- Low temp storage for foods
- Pasteurization followed by preventing contamination
What is the botulinum toxin resistant to?
Proteolytic enzymes in GI tract
What is Clostridium botulinum?
- Gram-positive (thick-walled), anaerobic, spore-forming bacterium
- Ubiquitous in soil
What is the causal agent of botulism?
A neurotoxin, heat-labile protein
Symptoms of botulism
- Nausea & vomitting = 12-24 hrs
- Weakness, double vision, lack of energy
- Death in 2-9 days from respiratory paralysis
Infant botulism
- C. botulinum can colonize infants’ (< 1 yr old) colon
- Spores present in honey and corn syrup
- “Floppy baby” syndrome may be responsible for some SIDS cases
- Symptoms = constipation, no facial expression, poor feeing, weak cry, reduced movement, drooling
Prerequisites for botulism toxicity
- Obligate anaerobe
- Water activity > 0.9 (water must be available)
- pH > 4.6 (low acid food)
What are 3 reasons to add nitrite to meats?
- Taste
- To fix color (pink of sausage)
- Inhibit growth of C. botulinum
Are nitrites carcinogens?
- Nitrites can make nitrosamines, which are carcinogens at high levels
- Food scientists can keep these levels very low
Botulism prevention
- Heat processing according to National Food Processors Association (NFPA)
- Refrigeration < 40 F
- Hygienic food handling, especially if pH > 4.6
- Heat food to boiling temp for 10 mins
How is home canned food a major source of botulism?
Insufficient processing of low acid foods such as green beans, veggies, fish, meats
What are Bacillus?
Aerobic, rod shaped, gram positive, spore-forming bacteria
Where does Bacillus cereus live?
In cereals and meat
What 2 toxins does B. cereus make? What are the symptoms associated with them?
- Small peptide = heat stable; vomitting 1/2-6 hrs after meal
- Large protein = heat labile; diarrhea 6-15 hrs after meal
What is the symptom of B. cereus in meat, milk, veggies, fish?
Diarrhea
What is the symptom of B. cereus associated with rice and some other starchy foods?
Vomitting
Food-borne infections
- Food is the vector that carries high levels of the pathogen to the body
- Illness caused by pathogen colonizing or invading the body
What bacterium causes Salmonellosis?
Salmonella enterica
What are the symptoms of Salmonella?
- Gastroenteritis
- Fever (typhoid)
- Diarrhea
- Cramping
How is salmonella transmitted?
By the fecal-oral route (food contaminated with feces)
Salmonellosis prevention
- Hygienic food handling
- High temps for cooking food
- Rigid temp control and hygienic practices for processed foods
In the U.S., what bacterium is the second leading killer due to food borne illness?
Listeria monocytogenes
What does listeria monocytogenes cause?
Meningitis (infection of the brain)
How is listeria monocytogenes particularly harmful to pregnant women?
This bacteria can cross the placental barrier to cause a fatal infection of the developing fetus
What is the USDA’s policy on listeria monocytogenes?
Zero tolerance
How fatal is listeria monocytogenes?
~25% fatal in susceptible individuals (pregnant women, very old, very young, those on immunosuppressant therapy, HIV)
Under what conditions does listeria monocytogenes thrive?
- High osmotic strength (deli meats)
- Temp < 7 C (45 F)
- Cross-contamination followed by refrigeration
In what foods is listeria monocytogenes most common?
- Low-acid cheeses
- Cured and raw meat products
What symptom does E. coli cause?
Dysentery (bloody diarrhea)
What foods is E. coli most common in?
Rare hamburgers, unwashed produce
What parasite causes trichinellosis?
Trichinella spiralis (trichina worm)
What foods can cause trichinellosis?
From undercooked pork, bear, dog, cat
How common is trichinellosis?
Rare in the U.S.
How can trichinellosis be prevented?
Freezing food for 3 weeks
What parasite causes anisakiasis?
Anisakis simplex (roundworm)
What food causes anisakiasis?
Undercooked fish (sushi)
How can you prevent anisakiasis?
Freeze food at -20 C for 24 hrs
What are the smallest pathogens?
Viruses
Where do viruses grow?
In the body, not food
How are viruses transmitted?
Through improper food handling
How do viruses multiply?
Hijack the host’s genetic & protein synthesis apparatus –> force it to make more viruses
Are viruses alive?
Not really
-No metabolism, no energy source, no metabolic waste
Why don’t antibiotics work on viruses?
Antibiotics interfere with microbial cell wall synthesis, protein synthesis –> viruses don’t have these
What is the common route for viruses?
Fecal to oral route
What does it mean that a virus is an obligate parasite?
No life without a host
How do infected people “shed” virus particles?
In feces
What is Hepatitis A?
Disease due to viral infection of the liver
Symptoms of Hepatitis A
Sudden fever, malaise, nausea, anorexia, abdominal discomfort, jaundice
What happens if Hepatitis A is left untreated?
Irreversible liver damage that can lead to death
How is Hepatitis A transmitted?
- Person-to-person contact through fecal contamination
- Any food handled by people (salads, shellfish)
What is another name for Norovirus?
Cruise Ship Virus
Symptoms of Hepatitis A
Sudden fever, malaise, nausea, anorexia, abdominal discomfort, jaundice
What happens if Hepatitis A is left untreated?
Irreversible liver damage that can lead to death
How is Hepatitis A transmitted?
- Person-to-person contact through fecal contamination
- Any food handled by people (salads, shellfish)
HACCP
Hazard Analysis & Critical Control Points
- Systematic approach to food safety
- Identifies factors where lack of control could potentially result in an unacceptable health risk
How is Norovisus transmitted?
Fecal-oral route
What is considered an infectious dose for Norovirus?
18 virus particles
In what foods is Norovirus most common?
- Water
- Raw or under-steamed shellfish
- Any foods handled by infected individuals
HACCP
Hazard Analysis and Critical Control Points
Two most important sanitation protocols
- Wash your hands
- Avoid cross contamination carried on cutting boards, knives, sponges, and hands
