Foodborne Illness

Foodborne Illness:

  • General Info about Microbes:

    • Composition of Microbes Contributing to Foodborne Illness:

      • 90% Bacteria, 6% Viruses, 3% Chemicals and 1% Parasites

    • Bacteria Info: 

      • Examples: e coli, salmonella, listeria, clostridium botulinum etc

      • Young children are vulnerable to e. Coli ; can have long-term health effects

      • Pregnant women are vulnerable to listeria 

      • Clostridium botulinum: contains a neurotoxin that is used to reducing wrinkling (botox) but can have health consequences especially when not handled by health professional

        • 1990-2005 indigenous population had significantly higher clostridium botulinum illnesses likely due to methods of preparation, consumption of country foods and environmental contamination. 

        • In the late 2000s, Clostridium botulinum illness rates were similar between Indigenous and non-Indigenous populations.

    • Virus Info:

      • Norovirus outbreak in guelph campuses

    • Parasite Info:

      • Outdoor water ways can be contaminated by parasites



numbers on slide #2 aren’t important to remember




  • Groups most at risk for foodborne illnesses: 

    • infants (underdeveloped immune system and environmental exposure)

    • elderly (nursing homes), patients with compromised immune systems, and pregnant/lactating women 

    • In nursing homes/long-term care facilities the staff can also contribute to increase of illness among patients 

    • Pregnant/lactating mothers 

  • Safe Food Storage:

    • Temperature abuse: improper storage of raw or cooked foods

    • Danger zone: 4 - 60 celcius; bacteria growth and toxin production

    • Slow Growth Zone: 4 - 0 celsius 

    • Freezing: bacterial growth stops but cells survive

    • Ideal Cooking Temperature Range: 74 - 100 celsius 

    • 60 - 74 celsius range: growth inhibited for most microbes except thermophiles  

    • Suggestions:

      • Let leftovers cool down but don’t leave them out at room temperature

      • JUST BECAUSE IT'S COOKED DOESNT MEAN YOURE OFF THE HOOK

  • Other Relevant Terms and Info

  • Cross Contamination: transfer of bacteria from handlers to raw food or from raw food to cooked food during preparation/storage 

    • Preventing Cross Contamination from Raw to Cooked Products: do not store raw foods above cooked foods in refrigerator

  • HACCP Principles: hazard analysis and critical control points

  • Critical control points: stages or steps in production where something could potentially go wrong (ex: heating, handling, packaging etc); controlling this decreases risk of hazard 

  • RTE: ready to eat 

  • GMP: good manufacturing process/practice

  • Application of HACCP Principles:

    • Training: gmp & hygiene training, technical training, sanitation training, communication

  • Sources of Contamination:

    • Environmental

    • Microflora (bacteria in intestines of animals and defacted via feces)

      • Risks of animal pooping near produce

    • Food handlers and utensils

    • Raw Ingredients: 

      • poultry (Salmonella spp)

      • beef (Escherichia coli)

      • Seafood: fecal coliforms (exposure to poorly managed sewage; often time affects oysters) and hepatitis A (abundant in warm climates)

      • Eggs/dairy: listeria monocytogenes 

    • Contact with Surfaces:

      • To avoid, take proper sanitizing measures:

        • Sanitize between batches 

        • Sanitizing products: chlorine (bleach), hydrogen peroxide, and ozone

          • Bleach as a sanitizer is diluted with water (Cl2 + H2O → HOCl + HCl) thus producing a weak hypochlorous acid and strong hydrochloric acid

          • Noname bleach: NaOCl (sodium hypochlorite, the salt of hypochlorous acid) 

          • HOCl inactivates bacteria and cell membranes of microbia 



  • Symptoms of Foodborne Illness:

    • Diarrhea: damage of intestinal wall

    • Fever/headache: response to fighting off virus/bacteria

    • Vomiting: intestinal effects

    • Fatigue: body expends energy to fight off illness

  • Classifying Foodborne Illness:

    • Bacterial Infection: the effect of micro-organism on gut wall 

      • Bacteremia: bacteria damage intestinal wall so much it enters bloodstream which impact other organs

      • Salmonellosis and listeriosis (-osis refer to inflammation) are illnesses arise from salmonella/listeria bacteria which are common drivers of bacterial infection

    • Intoxication/toxin-mediated infection: the effect of the toxin produced by the micro-organism in food item or within body

      • Toxin-mediated infection: microorganism is consumed then toxin is produced in body

        • Bacteria that produce this infection: clostridia spp. And potentially e.coli 0157:H7

      • Intoxication: toxin is produced in food and food is consumed

        • Bacteria that produce toxins in food: Staphylococcus aureus and clostridium botulinum (neurotoxin affecting nervous system)

  • Foods of Concern for Foodborne Illness Transmission

  1. Improperly stored or washed properly fruits/vegetables (ex: baked potatoes)

  2. Protein-rich foods:

  • Presence of amino acids facilitates growth of microorganisms and allows them to proliferate

  • Ground-beef has higher risk of contamination than other beef and meats because it has more moisture and more moisture due to grounding; also muscle tissue is sterile until punctured 

  • Highest risk: chicken and ground beef

  • High Risk: beef, steak and turkey

  • Medium Risk: bbq, deli meat, pork (not as many parasites in today age) and roast beef 

  • Low Risk: chicken nuggets, ham and sausage 

  1. High moisture content foods: 

  • mostly fresh foods like eggs, meats and fresh produce

  1. Low-acid foods: 

  • foods items at pH 4.5 or higher (such as tomatoes, baked beans, cream of mushroom soup)


Foodborne Illness Bacteria

  • Bacteria Morphology:

    • Bacilli: salmonella spp. (hot-dog shaped/rod)

    • Cocci: enterococci (sphere shaped) 

      • Entero-: associated with intestines/GI tract

      • Often come in clusters of 4

  • Bacteria Staining:

    • Gram stain is purple dye called crystal violet:

      • Bacteria retaining purple stain are referred to as: gram positive 

      • Bacteria that show pink stain are referred to as: gram negative

  • Bacteria Metabolism: certain sugars bacteria grow on

  • Bacteria Respiration Requirements: 

    • Aerobic Bacteria: requiring O2 for growth

    • Anaerobic Bacteria: prefer absence of O2 for growth (ex: clostridia)

    • Facultative Anaerobic Bacteria: grow in presence or absence of oxygen (ex: all salmonella, escherichia coli, staphylococcus aureus)

    • Microaerophilic Bacteria: requiring specifically 3-6% O2 for growth (ex: campylobacter jejuni)

  • Bacteria Environmental Tolerances:

    • Thermophiles: found on thermal vents are bottom of ocean

    • Halophiles: can grow at high salt concentrations 

      • Withstand osmotic effect

      • Ex: vibrio cholera (contaminate water supply and responsible cholera outbreaks)

  • Campylobacter Jejuni:

    • Gram negative, microaerophilic, spiral or S-shaped cells

    • Onset of symptoms: 2 - 5 days

    • Mild symptoms: abdominal pain and bloody diarrhea 

    • Self-limiting disease: illness that lasts for short duration in healthy individuals without need for treatment 

    • Food Sources: raw milk, poultry and meat

    • Only a small number of cells are required for infection

    • Primary mode of transmission: cross-contamination 

  • Escherichia Coli O157:H7:

    • Gram negative, facultative anaerobic, rod-shaped cells

    • Can be an infection or toxin-mediated 

    • Onset of symptoms: rapid 12 - 72 hours

    • Duration: 1 - 3 days

    • Symptoms: severe abdominal pain, nausea, vomiting, bloody diarrhea, kidney failure, and hemolytic uremic syndrome

    • Modes of transmission: cattle intestines, fruits falling to ground (orchard apples are at risk) that get fecal contamination and cross contamination 

      • E coli transmission into water:

  1. Dung holding tank leak into soil

  2. Dung spread across field as fertilizer

  3. Heavy rain carry bacteria to water table where well draws water

  4. Bacteria enter water system through crack in well and treatment plant 

  5. If water is not treated with chlorine it contaminate town water supply (walkerton tragedy) 

  • Walkerton Costs:

    • 7 deaths and 2500 illness

    • Those with acute gastroenteritis more likely to develop hypertension, renal problems and cardiovascular issues (the keypoint is walkerton tragedy left lingering problems)

  • Listeria Monocytogenes:

    • Gram positive, facultative anaerobic, short rod-shaped motile cells

    • Bacterial Infection 

    • Capable to grow at refrigerated temperatures and withstands salty/acidic foods

    • Symptom Onset: 1 day - 3 weeks

    • Duration: indefinite (NOT SELF LIMITING)

    • Symptoms: flu-like symptoms and life threatening complications, nausea, vomiting, headache, fever, chills and backache

    • Complications: in pregnant women and at-risk populations – septicemia (bacteria entering bloodstream), meningitis (brain), encephalitis (inflammation of brain) and birth defects (potentially stillbirths)

    • Food Sources: raw meat, raw poultry, dairy products, raw vegetables and seafood (CHOCOLATE BARS DAIRY PROTEINS)

      • Cause of recall of cheeses and chocolate bars

    • Mode of Transmission: naturally occurring in environment, cross contamination during or after processing and undercooked foods 

  • Salmonella spp.:

    • Gram negative, facultative anaerobic, short rod-shaped cells

    • Bacterial Infection:

    • Symptom onset: rapid self 

    • Duration: 2-3 days self limiting

    • Symptoms: abdominal pain, headache, nausea, vomiting, fever and diarrhea

    • Food Sources: chocolate, raw meats, chocolate, cream-filled desserts, and dairy products

    • Mode of Transmission: cross contamination with fecal matter and large scale processing facilities 

      • Outbreak with schneider lunchmates/lunchables

        • They recalled products and identified that the shredded cheese in the kits were contaminated salmonella

        • They traced it back to the suppliers of the dairy

  • Staphylococcus Aureus:

    • Gram positive, facultative anaerobic and cocci

    • Bacterial intoxication

    • Heat stable enterotoxin 

    • Symptom Onset: rapid 1 -6 hrs (2 -4 hrs)

    • Duration: 1-2 days

    • Symptoms: severe nausea, acute abdominal pain, vomiting and diarrhea 

    • Sources: naturally presence in nasal passage of healthy people, infect wounds/cuts, and present on hands/hair/nose/throat

    • Food Sources: found in ready to serve foods due to cross contamination, RTE luncheon meat, meat/poultry, prepared vegetables/egg salads, custards and dairy products

    • Modes of Transmission: contamination from food handlers and an issue with foods that require a lot of preparation and handling 

      • Bacteria spread through aerosol droplets (talking and sneezing/coughing)

      • Improper use of tasting spoons

      • Steak tartare is highly prepared and handled item (personal anecdote by professor yuan)

January 24th, 2025

  • Clostridia spp.

    • Gram positive, anaerobic, and spore-forming bacilli

      • The bacteria spore forming capacities allow it to withstand harsh environmental stressors (heat treating, freezing, salty, acidity and dehydration)

      • Can exist in a separate dormant spore form

    • Main Species (spp.) of Concern: 

      • Clostridium Perfringens: toxin-mediated infection

      • Clostridium Botulinum: intoxication 

      • Clostridium Difficile: toxin-mediated infection, associated with patients taking antibiotics (antibiotics may target healthy bacteria, allowing other harmful bacteria to proliferate in the intestine), and fecal contamination 

  • Clostridium Perfringens (cont’d):

    • Symptom Onset: 8 - 22 hrs (less than a day)

    • Duration: 1 day or less

    • Symptoms: abdominal pain and diarrhea

    • Sources: common in most foods and meat products that have been allowed to cool slowly and served cold or poor reheated

    • Food Sources: spices, gravy, improperly cooled foods, and temperature abused foods then reheated 

  • Clostridium Botulinum (cont’d):

    • Gram positive, anaerobic, spore-forming bacilli

    • Produces a neurotoxin

    • Heat resistant 

    • Duration: days to a year (dependent on the symptoms)

    • Symptoms: fatigue, headache, dizziness, vision problems, trouble, swallowing, and respiratory paralysis (severe) 

    • Commercial Purpose: used for cosmetic purposes, relax the muscles botox and relieve intensity of cerebral palsy 

    • Sources: low-acid foods, packaged in anaerobic container and held in the danger zone 

    • Food Sources: canned green bean, cream of mushroom soup, baked beans, bottled garlic/onions canned with oil 

    • Increased Risk: home-canning



Non-bacteria Foodborne Illness 

  • Norwalk/Norwalk-like Virus:

    • Alias: winter vomiting disease

    • Genus: norovirus

    • Family: caliciviridae

    • Duration: 2-3 days (Self limiting)

    • Symptoms: abrupt onset of diarrhea (non-bloody), cramps, low-grade fever 

      • Symptoms can persist for weeks 

    • Mode of Transmission: contamination via fecal matter from infected food handlers, raw sewage in water, and water sources (water/shellfish/salads)

    • Increased Sites of Risk: cruise ships, daycares and long-term care homes

  • Aspergillus Flavus (MOLD):

    • Produces aflatoxin

    • MOLD

    • associated with liver cancer in humans

  • Cyclospora/Cyclosporidia (parasite):

    • Parasite associated with fresh berries

    • Symptom: prolonged diarrhea 

  • Giardia (parasite):

    • Giardia lamblia

    • Illness: giardiasis (aka beaver fever)

      • Symptoms: stomach cramps, bloating, nausea and bouts of watery diarrhea (generally gastrointestinal discomfort) 

    • associated with animal fecal contaminated water sources 

    • Associated with hiking 

  • Trichinellosis:

    • Trichinella Spiralis: roundworm

    • associated with undercooked meats (primarily pork) 

    • Symptoms: nausea, vomiting, diarrhea, sweats/fever and muscle pains

      • Causes muscle pain because it invades the muscle

    • Pigs in modern farms are housed indoors so the risk of this parasite has reduced since improved farm practices