Microbial Pathogenesis

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  1. Pathogenicity
    The ability to cause disease by overcoming the defenses of a host
  2. Virulence
    The degree of pathogenicity of a microorganism
  3. What does ID50 stand for?
    Infectious dose for 50% of test population
  4. What does LD50 mean?
    Lethal dose (of a toxin) for a 50% of the test population
  5. Portals of entry
    • Avenues in which pathogens can gain entrance to the human body
    • Mucous membrane 
    • Skin
    • Parenteral route
  6. Easiest and most frequently traveled protal of entry
    Mucous membrane of the respiratory tract
  7. Bacillus anthracis ID50 for skin, inhalation, ingestion
    • Skin: 10-50 endospores 
    • Inhalation: 10,000-20,000 endospores
    • Ingstion: 250,000-1,000,000 endospores

    Showing that cutaneous anthrax is significantly easier to acquire than other forms
  8. Virulence factor
    A product of microbes such as an enzyme of toxin that increases its invasiveness of pathogenicity
  9. Examples of microorganism virulence factors
    • Toxin production
    • Enzyme production
    • Capsule production
    • Adhesion Production
  10. LD50 of Botulinum
    0.03 ng/kg
  11. LD50 of Shiga toxin
    250 ng/kg
  12. LD50 for Staphylococcal enterotoxin
    1350 ng/kg
  13. Exotoxin
    • Proteins produced by pathogenic bacteria as a part of their growth
    • Small amounts can be quite harmful
  14. Endotoxin
    Lipid portions of the lipopolysaccharide of the outer membrane of cell wall of gram (-)
  15. Exotoxins are mostly produce by what type of bacteria?
    Gram (+) and only some gram (-)
  16. What carries most(perhaps all) exotoxins?
    Bacterial plasmids or phages
  17. Diffusion of exotoxins in human host
    The are rapidly diffused in body fluids and rapidly transported throughout the body
  18. What do exotoxins do to the body?
    • Destroy particular parts of the hosts call or by inhibiting certain metabolic functions.
    • Highly specific in their effects to body tissues
    • Making them the most lethal substances known
  19. Neurotoxins
    Toxins that attack nerve cells
  20. Cytotoxins
    attack a wide variety of cells
  21. Enterotoxins
    Attack the lining of of the gastrointestinal tract
  22. About exotoxins
    • Part of the outer membrane of G(-) bacterial cell wall (lipopolysachharide)
    • Activate blood clotting proteins
  23. When are endotoxins released?
    When a gram(-) dies and lyses
  24. Difference between exotoxin and endotoxin
    • Exotoxin is a protein produced normally by g(+) cells and edotoxins are lipopolysaccharides that lay on their out membrane of the cell wall of g(-) cells
    • Exotoxins target specific organs and endotoxins produce an overall physiological effect
  25. What happens when you treat diseases caused by gram (-) bacteria?
    Cells lyse, releasing their endotoxins and may lead to immediate worsening of symptoms followed by improved conditions
  26. Cytokines
    • Release by macrophages when ingesting a gram(-) bacteria, due to their endotoxins 
    • Cytokines are then release into blood stream
    • Traveling to hypothalamus 
    • Raising the temperature
  27. Coagulase enzyme
    • Reacts with fibrinogen to form a fibrin coat 
    • Protecting from phagocytosis and blood antibodies
  28. Hemolysins
    • RBS lysis 
    • Done for nutrition
  29. Collagenase enzyme
    • Breaks down collagen 
    • Helps spread GAS, 
    • Gangrene
    • Cloststridium 
    • Pseudomonas
  30. Leukocidin enzyme
    Destroys WBC
  31. Kinases enzyme
    Breaks down fibrin clots and raise the spread of infection
  32. What specific factors lower human resistance to infection
    • Immunocompromised (HIV, cancer, organ transplant)
    • Underlying illness
    • Substance abuse 
    • Malnutrition 
    • Stress/ lack of sleep
    • Antibiotic therapy 
    • Hospitalization
  33. Capsule Production
    • Usually made from sugars 
    • Adherence and disguise 
    • Antiphagocytic
  34. Adhesin Production
    • Fimbriae
    • M protein (strep)
    • Surface molecules that bond to specific complementary host cell receptors
  35. Danger zone for improper food handling/storage
  36. Refrigerator Best
  37. Foods less vulnerable to foodborne illness
    Dried food, jams, honey, brined
  38. What is a red flag for foodborne illnesses?
    Raw meat/chicken
  39. Intoxication
    • Ingestion of preformed Toxin 
    • Very sudden onset 
    • Target Organ Affected 
    • No Antibiotic Treatment 
    • May give antitoxin (antibodies)
  40. Infection
    • From improper cooking/handling 
    • Bacteria multiply in food 
    • Call invade body
    • Delay in symptoms 
    • Effect felt 24-48 hours
    • Usually consists of fever 
    • Antibiotic treatment possible
  41. Botulism (Patohgen, symptoms, intox vs infec)
    • Clostridium Botulinum (GPR)
    • Endospores 
    • Soil, Fresh water sediment
    • Intoxication 

    6-12 hours: Vomiting, blurred vision, flaccid paralysis, worst case death
  42. Botulism treatment
    • Treat with Trivalent Antitoxin 
    • Low acid foods under anaerobic conditions 
    • Commercial Canning Aim is "Bot Kill"
    • Toxin Denatures w/10 min of boiling 
    • Nitrates are added to food to inhibit growth
  43. Infant Botulism
    • Endospores in Honey
    • Pasteurization has effect 
    • High sugar prevents germination
    • Infection THEN intoxin
    • Do not give children honey for 24 months
  44. Staphylococcal Food Poisoning 
    (Pathogen, transmission, habitat, toxin vs infection)
    • S. Aureus, GPC
    • Intoxication caused by entertoxin
    • High Osmotic Pressure Foods 
    • Normally found on skin, nose, throat
    • Commonly transferred to food
    • If allowed to incubate in food, enterotoxins are produced
  45. S. aureus (Disease, symptoms)
    • Staphylococcal Food Poisoning 
    • Vomiting, Diarrhea, Gas
    • Usually lasts about 12 hours
  46. Clostridium Botulinum (Disease, transmission, symptoms)
    • Botulism/ Infant botulism 
    • Vomiting, blurred vision, flaccid paralysis (6-12 hours)
    • Endospores in Soil, freshwater
  47. Campylobacter Gastroenteritis (Pathogen, transmission, toxin vs infection, symptoms, treatment)
    • Campylobacter jejuni (GNR, Microareophile) 
    • Almost all retail chicken contaminated 
    • Fever, cramping, diarrhea or dusentery
    • Infection & Intoxication 
    • Antibiotic treatment w/relapses 
    • 1 week recovery
  48. Salmonellosis (pathogen, Symptoms, transmission, treatment, infection vs intoxication)
    • Salmonella enteriditis (GNR)
    • Fever, nausea, pain, cramps, diarrhea
    • Transmitted through meat products (Poultry, eggs)
    • No vaccine (~2,000 strains)
    • Infection, intoxication
  49. Typhoid Fever (Pathogen, mortality rate)
    • Salmonella typhi (GNR)
    • High Mortality (~20%)
    • Some people become carriers
  50. E Coli Gastroenteritis (Symptoms, Cause, infection vs intoxication)
    • GNR Coliform, multiple strains 
    • Causes mild dysentery (Watery diarrhea) 
    • Infection and Intoxication
    • Primary cause of Travelers Diarrhea
  51. E. Coli (0157:H7)
    • Enterohemmorrhagic strain
    • Severe bleeding, may lead to systemic disease (High mortality rate)
    • Causes Hemolytic Uremic Syndrome (HUS) in 5-10% of children
    • Transmitted from raw meats, raw spinichm alfalfa sprouts
  52. Bacillus cereus Gastroenteritis
    • GPR Aerobic
    • Spore former found in soil
    • Wide pH and temp tolerance 
    • Spores germinate in cooked food as it cools 
    • Rapid growth, TOXINS
    • Rapid onset (2 hrs)
    • Self-limiting
  53. J. Paralytic Shellfish Poisoning
    • Dinoflagellates during red tide
    • Accumulates in shellfish
    • Saxitoxin (Neurotoxin)
  54. Percentage of food poisoning sources
    • 35% Home food handling mistakes outside of home
    • 20% Home-Prepared food
    • 7% Mistakes in manufacturing 
    • 38% unknown
Card Set:
Microbial Pathogenesis
2014-05-21 19:32:31
Micro final chp 15
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