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Microbial pathogenicity No Slide Title diphtheria

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Microbial pathogenicity No Slide Title diphtheria Powered By Docstoc
					Communicable disease
    Transmitted from person to person
      Robert Koch - anthrax
      Koch’s postulates
            1. Organism present in every case of the disease
            2. Organism isolated and grown in pure culture
            3. Healthy animal inoculated with organism has
                   disease
            4. Organism re-isolated from test case
            Problems:     T. pallidum
                          ethics
Microbes and the human body
             Table 14.1
      Roles of normal flora
             physical - fill ‘sites’ non-infectious for site
             metabolism - generate unfavorable conditions
             stimulate immune system
      Benefit to microorganism
             warm, moist environment
             nutrients provided
             environmental needs met (oxygen)
Infection - presence of microorganisms
Disease - alteration in physical state of the body
       Will infection result in disease?
       Dosage of microorganisms: ID50
       Host resistance
       Pathogenicity: ability to cause disease
Pathogenicity - ability to cause disease
      due to virulence factors which allow them to invade
      and disrupt body functions; host may attenuate so
      symptoms not overt
Virulence
       how potent a pathogen
       depends on Invasiveness and Toxigenicity
       depends on survival during transmission
       depends on host resistance
Opportunists
     not pathogens, but often associated with the body
     a change in body function or status may result in disease
             other diseases - diabetes, AIDS, CF
             antibiotic therapy
             burns
     transfer of organism to an abnormal spot
             catheters, surgery (E. coli and UTI)
Survival - adaptation to host’s immune system response
      successful pathogen not too virulent
Virulence depends upon:
Invasiveness
       ability to invade and attach to tissues, to multiply
          (normal flora non-invasive for surfaces they
                normally inhabit)
          (some cause superficial infections, others deeper)
       may be attenuated by the immune system
Toxigenicity
      ability to produce toxins which disrupt cell function or
      destroy cells or tissues; may cause death
              (may not need organisms: botulism; S. aureus
      LD50 lethal dose for 50% of test cases
PORTALS OF ENTRY
    Mucous membranes: respiratory, GI, GU, conjunctiva
                               air        food, water, objects
    Skin: pores (sweat glands), hair follicles
    Parenteral: damage to barrier
          punctures, insect bites, cuts, drying


    Adherence - attachment to tissue
          adhesins - surface receptor on host cell
          capsules
          cell wall components
          fimbriae
            (S. mutans, Actinomyces, N. gonorrhea)
Defeating host defenses
      Invasion of host cells - evade immune system
             Shigella, E. coli, Legionella
              prevent lysosome fusion
              protected from digestive enzymes
      Capsules - inhibit phagocytosis
            S. pneumoniae, H. influenzae, Y. pestis
      Cell wall
             S. pyogenes M protein - resists phagocytosis
             M. tuberculosis waxes - resists digestion
      Endotoxin - lipopolysaccharide, LPS
            non-specific
            blood clotting, internal hemorrhaging,
            inflammation, hypotension
Defeating host defenses
      Protein toxins - categorize by symptoms or disease
             specific organism
             specific effects
             distinctive clinical symptoms
             heat sensitive - most are
             EXOTOXINS
             potent
Bacterial Toxins

Toxin              Dose (mg)  Host    Endotoxin   Snake venom
Botulinum D        0.8x10-8  Mouse     3x107        3x105
Tetanus            4x10-8    Mouse
Shigella           2.3x10-6  Rabbit    1x107        1x105
  neurotoxin
Diphtheria         6x10-5    Guinea    2x104        2x102
                               pig
PROTEIN TOXINS
A. Neurotoxins
      C. botulinum progenitor toxin
      C. tetani tetanospasmin
      Shiga toxin
B. Enterotoxins
       V. cholerae cholaragen
       S. aureus enterotoxin
C. Cytotoxins - cell death to cell lysis
      C. diphtheriae and P. aeruginosa
      Hemolytic toxins (Staphylococcus, Streptococcus,
              Clostridium)
          RBC: , ,  hemolysis
          WBC: leukocidin (S. aureus)
PROTEIN TOXINS
A. Neurotoxins
      C. botulinum progenitor toxin
      C. tetani tetanospasmin
      Shiga toxin
B. Enterotoxins
       V. cholerae cholaragen
       S. aureus enterotoxin
C. Cytotoxins - cell death to cell lysis
      C. diphtheriae and P. aeruginosa
      Hemolytic toxins (Staphylococcus, Streptococcus,
              Clostridium)
          RBC: , ,  hemolysis
          WBC: leukocidin (S. aureus)
      Dermonecrotic (S. aureus)
      Necrotizing fasciitis (S. aureus)
PROTEIN TOXINS
D. Exoenzymes
      Protease
      Phospholipase
      Hyaluronidase
      Collagenase
      Fibrinolysin - Streptokinase, Staphylokinase
      Coagulase
      Exfoliatin - Scalded skin syndrome
PROTEIN TOXINS
D. Exoenzymes
      Protease
      Phospholipase
      Hyaluronidase
      Collagenase
      Fibrinolysin - Streptokinase, Staphylokinase
      Coagulase
      Exfoliatin - Scalded skin syndrome
PROTEIN TOXINS
E. Toxic Shock Syndrome Toxin (TSST-1)
       Toxic Shock Syndrome
     generally severe to fatal, even with antibiotic treatment
       Syndrome: sudden onset
              fever, diarrhea, vomiting, hypotension, rash
              renal and muscle damage
       Two toxins: enterotoxin - TSST-1 (superantigen)
                   pyrogenic toxin


OTHER TOXINS
    Aflatoxins - fungi (grains)
    Alkaloids - LSD, ergot alkaloids (grains)
    Aminitin - mushrooms
PLASMIDS & BACTERIOPHAGE
    plasmids: botulism, coagulase
    phage: diphtheria toxin, erythrogenic toxin (S. pyogenes)
           TSST-1

				
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posted:1/17/2011
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