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Foodborne pathogens It can be classified into three forms: foodborne intoxication PowerPoint Presentation
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Foodborne pathogens It can be classified into three forms: foodborne intoxication

Foodborne pathogens It can be classified into three forms: foodborne intoxication

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Foodborne pathogens It can be classified into three forms: foodborne intoxication

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  1. Foodborne pathogens It can be classified into three forms: foodborne intoxication foodborne infection foodborne toxicoinfection

  2. E.coli Botulinum Salmonella Campylobacter Listeria Staphylococci Food Pathogens www.textbookofbacteriology.net Todar's Online Textbook of Bacteriology • Microrganisms that cause food borne infection or intoxication:

  3. Foodborne Intoxication • illness from microbial exotoxin • microorganism does not cause the illness, the toxin released by the microorganism does • common exotoxin producing microorganisms • Staphylococcus aureus • Clostridium botulinum

  4. INTOXICATION • Ingestion of FOOD CONTAINING TOXIN causes illness • Microbes produce toxin while growing in food • Ingestion of the microbes themselves may be harmless

  5. Food borne intoxication • some bacteria grow in food and produce a toxin within the food which is then consumed e.g. Bacillus cereus and Staphylococcus aureus. When the food is consumed viable cells of the bacteria do not need to be present.

  6. Following ingestion, Toxins are absorbed through the gastrointestinal epithelial lining and cause local tissue damage and may induce inflammation resulting in diarrhea or vomiting. In some cases, toxins are translocated to distant organs or tissues such as liver, kidney, peripheral, or central nervous system where they can cause damage.

  7. Food Poisoning/intoxication Staphylococcus aureus

  8. Staphylococcal Toxin-Mediated Diseases: Food Poisoning

  9. Exotoxins • most exotoxins are grouped according to the tissues they adversely impact • neurotoxins damage the nervous system • entereotoxins upset the intestinal system • cytotoxins afflict their damage on many different types of cells by disrupting cellular function of by lysing the cell

  10. Staphylococcus aureus • Intoxication by consumption of heat stable, preformed toxin in food • Symptoms • vomiting (“projectile”) • nausea • abdominal cramps • and diarrhea 1-6 hours after eating food contaminated with toxin • Bacteria killed by mild heat. Toxins are very heat stable. • Will grow with or without air; toxin not usually produced in acid food; bacteria are resistant to high salt (up to 15%)

  11. Bacteria Causing Intoxications • Staphylococcus aureus (“Staph”) • Reservoir: Common on human skin and in nasal cavity--therefore commonly a problem in foods that are handled a lot • Transmission: Must multiply in food to produce enough toxin to cause illness • Disease: Primarily causes vomiting • Incubation period: Short; usually 2 - 4 hours • The bacteria is killed by cooking, however the toxin is not destroyed by normal cooking!

  12. St. aureus and food • Staph grows and divides in food and produces an enterotoxin • The Staph doesn’t cause food poisoning, the enterotoxin does • Enterotoxin is stable to heating at 100oC for 30 minutes. • Enterotoxin is resistant to degradation by stomach gastric acids

  13. St. aureus and food poisoning • St. aureus causes gastro-enteritis • Food poisoning is not caused by the organism but by the toxin that the organism secretes • St. aureus food poisoning is the most common form of food poisoning in the US

  14. How did the chef get a staph infection? • Staph is often found on skin surfaces because they can tolerate the low moisture and high salt content of skin • Staph can easily spread from person to person via hand to hand contact • Staph can penetrate the deep tissues of skin damaged by burns cuts insect bites skin diseases—acne, eczema

  15. Normal Flora • the presence of normal flora • cover potential adherence sites for invading microorganism • Normal microflora : produce compounds toxic to other microorganisms bacteria found on skin

  16. What happens when Staph enters a wound and how does this relate to food poisoning ? • Localized staph infection leading to an abscess boils=abscesses in the skin carbuncle=interconnected abscesses • Rupture of the abscess leads to the release of live bacteria and associated toxin

  17. How do abscesses and boils form? • Chef cuts arm and Staph enters deeper skin layer • St. aureus is surrounded by a capsule thick slime layer that prevents an immediate immune response • Bacteria multiply at the site surrounded by the capsule • St. aureus establishes intimate contact with skin cells via bacterial techoic acids and fibronectin skin cell receptors

  18. Staph enterotoxin causes gastro-enteritis in two ways • VOMITINGtoxin works on the vomiting control center of the brain this leads to reversal of peristalsis and vomiting • DIARRHEAenterotoxin is a superantigen and elicits a strong immune response in the region where the toxin is most concentrated. Immune response causes a loss of brush borders in intestinal epithelial cells; these cells cannot absorb water from the gut.

  19. Folliculitis manifests as superficial pustules or inflammatory nodules surrounding hair follicles.

  20. Furuncles (boils) are tender nodules or pustules caused by staphylococcal infection. Carbuncles are clusters of furuncles that are subcutaneously connected.

  21. Carbuncles

  22. Cutaneous Abscess • A cutaneous abscess is a localized collection of pus in the skin and may occur on any skin surface.

  23. Erysipelas is characterized by shiny, raised, indurated, and tender plaque-like lesions with distinct margins. It is most often caused by β-hemolytic streptococci and occurs most frequently on the legs and face.

  24. Impetigo (Bullous) Impetigo (Non-Bullous) Bullous impetigo is a superficial skin infection that manifests as clusters of vesicles or pustules that enlarge rapidly to form bullae. The bullae burst and expose larger bases, which become covered with honey-colored varnish or crust. Non-bullous impetigo is a superficial skin infection that manifests as clusters of vesicles or pustules that rupture and develop a honey-colored crust.

  25. Ecthyma gangrenosum is a bacterial skin infection (caused by Pseudomonas aeruginosa) that usually occurs in people with a compromised immune system. Ecthyma is a skin infection similar to impetigo, but more deeply invasive. Usually caused by a streptococcus infection, ecthyma goes through the outer layer (epidermis) to the deeper layer (dermis) of skin, possibly causing scars.

  26. Necrotising fasciitis

  27. The action of cholera enterotoxin is shown in Figure 21.22.

  28. Clostridium botulinum (anaerobic, intoxication) • Potent, Heat labile Neurotoxin • A few nanograms of toxin can cause illness • 180F for 10 minutes • Spores are heat resistant • High mortality rate • Associated with inadequately processed home canned food • Widely distributed in nature

  29. Clostridium botulinum • Associated foods • Low acid canned foods • Sausages • Meat products • Canned vegetables • Seafood • Almost any type of food that is not very acidic (pH > 4.6) can support growth and toxin production

  30. Exotoxins • exotoxins are highly specific • exotoxins are among the most lethal substances known to man • 1 gram of the exotoxin produced from Clostridium botulinum is capable of killing the entire population of the United States, close to 300 million people • the danger with exotoxins is not the ingestion of the bacterium, but the ingestion of the toxin Clostricium botulinum

  31. Clostridium botulinum (“botulism”) • Reservoir:Spores found in soil and water (ocean/lakes) • Transmission: Associated with improperly canned foods and ground-harvested foods such as onions and garlic • Disease: Toxin causes paralysis • Incubation period: ½ day to 3 days • Spore is difficult to destroy, but botulinum toxin CAN be destroyed by cooking (e.g., 176F for 10 min)

  32. Botulinum toxin consists of seven related toxins that are the most potent biological toxins known (Figure 21.20).

  33. Botulism (C. botulinum): • The most potent toxin known; few cases but high mortality (25%); destroyed by 10 min in 80 oC • paralysis of muscles • Common in soil and water • How? Improper canning  spore germination  toxin production  canned food used without cooking  disease

  34. All four types of botulism result in symmetric descending flaccid paralysis of motor and autonomic nerves always beginning with the cranial nerves. These symptoms are preceded by constipation in cases of infant botulism. • Symptoms include: • Double or blurred vision • Drooping eyelids • Dry mouth • Difficulty Swallowing • Muscle weakness

  35. Prevention • Proper food preparation is one of the most effective ways to limit the risk of exposure to botulism toxin. • Boiling food or water for ten minutes can eliminate some strains of Clostridium botulinum as well as neutralize the toxin as well. However, this will not assure 100% elimination. • Limiting growth of Clostridium botulinum and the production of botulism toxin is an alternative to their outright destruction.

  36. Temperature, pH, food preservatives, and competing microorganisms are among the factors that influence the rate and degree of Clostridium botulinum growth. • Growth of most strains of Clostridium botulinum will not occur below 10 or above 50 degrees Celsius.

  37. Clostridium botulinum will not grow in media with pH values lower than about 5. • Food preservatives such as nitrite, sorbic acid, parabens, phenolic antioxidants, polyphosphates, and ascorbates inhibit the growth of the microorganism.

  38. Clostridium botulinum will not grow in media with pH values lower than about 5. • Food preservatives such as nitrite, sorbic acid, parabens, phenolic antioxidants, polyphosphates, and ascorbates inhibit the growth of the microorganism.

  39. Lactic acid bacteria including Lactobacillus, Pediococcus, and Pactococcus can inhibit the growth of Clostridium botulinum by increasing the acidity of the medium. • While the cause of roughly 85% of infant botulism cases is unknown, in up to 15% of infant botulism cases the causes was ingestion of honey. Infants younger than one year old should not be fed honey.

  40. Avoiding Exposure • Avoid home-processed foods if at all possible, especially those with a low salt and acid content. • Botulism toxin is destroyed at a temperature of 176 F, thus if you must eat home-processed foods, boil them for 10 minutes before eating if at all possible. • If canning vegetables, use a pressure cooker, as it will kill any spores because it can reach temperatures above boiling.

  41. Foodborne Infection • requires consumption of microorganism • symptomatic about 1 day following ingestion of contaminated food • common foodborne infecting microorganisms • Salmonella • poultry product infections • Escherichia coli 0157:H7 • undercooked hamburger Campylobacter Salmonella

  42. food borne infectionInfections occur when pathogens are ingested via contaminated food and the bacteria is established in the body • usually growing inside the intestinal tract and irritating intestines. • The infection may involve subsequent growth in other tissues

  43. Direct contact e.g., coughing, sneezing, body contact Indirect contact vehicles (e.g., soil, water, food) Transport of the Bacterial Pathogen to the Host

  44. Adherence structures: Structures such as such as pili and fimbriae and specialized adhesion molecules on bacterium’s cell surface bind to complementary receptor sites on host cell surface Colonization: Colonization is the establishment of a site of microbial reproduction on or within host does not necessarily result in tissue invasion or damage Attachment and Colonization by the Bacterial Pathogen

  45. Principles of Infectious Disease • virulence factors are substances or features of a microorganism that help it infect and cause disease • they may include • ability to adhere • ability to overcome host defense • ability to evade host defense

  46. Factors: number of organisms present the degree of virulence of pathogen virulence factors e.g., capsules, pili, toxins host’s defenses or degree of resistance Factors Impacting Outcome of Host-Parasite Relationships