Communicable disease Transmitted from person to person

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Communicable disease Transmitted from person to
person Robert Koch - anthrax Kochs
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
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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)
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Infection - presence of microorganisms Disease -
alteration in physical state of the body Will
infection result in disease? Dosage of
microorganisms ID50 Host resistance Pathogenici
ty 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
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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 hosts immune
system response successful pathogen not too
virulent
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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
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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)
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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
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Defeating host defenses Protein toxins -
categorize by symptoms or disease specific
organism specific effects distinctive
clinical symptoms heat sensitive - most are
EXOTOXINS potent
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Bacterial Toxins Toxin Dose
(mg) Host Endotoxin Snake venom
Botulinum D 0.8x10-8 Mouse 3x107
3x105Tetanus
4x10-8 MouseShigella 2.3x10-6 Rabbit
1x107 1x105 neurotoxinDiphtheria
6x10-5 Guinea 2x104 2x102
pig
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PROTEIN TOXINSA. 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)
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PROTEIN TOXINSA. 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)
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PROTEIN TOXINSD. Exoenzymes Protease Phospholip
ase Hyaluronidase Collagenase Fibrinolysin -
Streptokinase, Staphylokinase Coagulase Exfoliat
in - Scalded skin syndrome
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PROTEIN TOXINSD. Exoenzymes Protease Phospholip
ase Hyaluronidase Collagenase Fibrinolysin -
Streptokinase, Staphylokinase Coagulase Exfoliat
in - Scalded skin syndrome
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PROTEIN TOXINSE. 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
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PLASMIDS BACTERIOPHAGE plasmids botulism,
coagulase phage diphtheria toxin, erythrogenic
toxin (S. pyogenes) TSST-1