PATHOLOGY the study of disease

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PATHOLOGY - the study of disease Etiology -
the cause of disease Pathogenesis - the
course of the disease development Disease
pathology - changes in the body caused by
disease INFECTION - invasion of the body by a
pathogen DISEASE - change in health due to the
infection Carrier - infected person without
detectable signs Normal flora ETIOLOGY OF
DISEASE - cause of disease
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CLASSIFYING INFECTIOUS DISEASE Symptoms -
subjective changes Signs - objective changes
observable changes Syndrome - specific symptoms
signs which accompany a particular
disease CLASSIFICATION OF DISEASE Communicable
disease Contagious disease Non-contagious
disease
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OCCURRENCE OF DISEASE Incidence of disease -
fraction of population contracting disease
during a particular period Prevalence of disease
- fraction of population with disease at a
specified time Incidence Prevalence -estimate
occurrence tendency for a disease to occur
more frequently in certain groups OCCURRENCE OF
DISEASE Endemic - constantly present Epidemic -
large number of new cases in short
period Pandemic - world-wide epidemic
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SEVERITY OF DISEASE Acute - rapid onset, short
duration Chronic - slower onset, long
duration Latent disease
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HOST INVOLVEMENT Local infection vs. Systemic
infection Focal infection - starts in one spot,
spreads Bacteremia - bacteria in the
bloodstream Septicemia - bacteria multiply in
the bloodstream Toxemia - toxins in the
blood Primary infection - initial cause of
illness Secondary infection - opportunists take
advantage (may be more serious than primary
infection)
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SOURCES OF PATHOGENS TRANSMISSION Reservoirs
Human reservoir - TB, leprosy Animal
reservoir - zoonoses - lyme disease,
rabies Inanimate reservoirs - anthrax,
giardia Transmission Direct contact Indirect
contact fomites Droplet transmission
sneezing, coughing Vehicle transmission food,
water, blood Vector transmission
insects NOSOCOMIAL INFECTION - hospital
acquired Compromised host Normal flora - some
opportunists Chain of transmission
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Epidemiology Study of when where diseases
occur and how they are transmitted Conside
r age sex occupation
socioeconomic status immunization
common history same food, restaurant
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MICROBIAL DISEASE Will infection result in
disease? Dosage of microorganisms ID50 Host
resistance Pathogenicity ability to cause
disease Pathogenicity 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
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Invasiveness ability to invade and attach to
tissues, to multiply (normal flora
non-invasive for normal surfaces) Toxigenicity ab
ility to produce toxins which disrupt cell
function or destroy cells or tissues may cause
death 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 capsules fimbriae (S.
mutans, Actinomyces, N. gonorrhea)
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DEFEATING HOST DEFENSES Capsules - inhibit
phagocytosis S. pneumoniae, H. influenzae, Y.
pestis Cell wall S. pyogenes M protein -
resists phagocytosis M. tuberculosis waxes -
resists digestion LPS Protein
toxins specific organism specific
effects distinctive clinical symptoms heat
sensitive EXOTOXINS potent categorize by
symptoms or disease
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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. pyogenes)
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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 PLASMIDS BACTERIOPHAGE plasmids
botulism, coagulase phage diphtheria toxin,
erythrogenic toxin (S. pyogenes) TSST-1