Immunology 2

• "Pathos" means?

  Suffering
• "Logos" means?

  Study
• Cause of disease; Origin

  Etiology
• Pathogenesis - development of disease, chains of events that lead to that disease
• Infection - invasion or colonization by the body of microorganisms (microbiological)

  • May exist in the absence of detectable disease about the count

  Ex.:

  • E. coli- cause gastrointestinal disease 
• Disease - abnormal state of all body; about the effect
• Infection

  • invasion or colonization of the bodily pathogenic microorganisms
  • May exist (-) of disease
  • EX: Virus > AIDS
  • Specific microorganism in a part of the body where it is not normally found
• Disease

  • abnormal state in which part or all pf the body is not properly adjusted or incapable of performing its normal functions.
  • occurs when an infection results in any change from a state of health
• Normal Microbiota

  • microorganisms that establish more or less permanent residence (colonize) but do not produce disease under normal conditions.
  • microbial ANTAGONISM / competitive exclusion; compete with pathogen
• Transient Microbiota

  • microorganisms that are present for days, weeks, months and THEN DISAPPEAR.
• Factors Affecting Distribution and Composition

  1. Nutrients
  2. Physical & Chemical
  3. Defenses of the Host
  4. Mechanical
• Normal Vs. Pathogenic Microorganism

  1. Competing for nutrients
  2. Producing toxins (bacteriocin)
  3. Altering pH
  4. Affecting oxygen availability
  5. Occupying space
• Normal Microbiota and the Host: Microbial Antagonism /Competitive Exclusion

  • preventing overgrowth of harmful microorganism
  • competition among microbes (nutrients, producing harmful substances, pH, oxygen.)
• Parasitism

  one organism benefits by deriving nutrients at the expense of the other
• Normal Microbiota and the Host: Opportunistic Microorganism

  • DO NOT cause disease in their normal habitat in health person but may do so in a different environment.
  • E.g., microbes through broken skin or mucous membranes which weakened or compromised by infection such AIDS
• Polymicrobial disease needs cooperation
• Symbiosis - relationship between two organisms in which at least one organism is dependent on the other.
• Commensalism - one of the organisms benefits and the other is unaffected.

  • e.g. corynebacteria - in eyes
  • e.g. saprophytic mycobacteria - in ears and external genitals
• Mutualism - benefits both organisms.

  • E. coli synthesize Vit. K and some Vit. B
  • Probiotic - Lactic Acid Bacteria (LAB)
  • Prebiotic - Chemicals that promote growth of beneficial bacteria.
• Exceptions to Koch's Postulates

  
  

  Some microbes CANNOT BE cultured on artificial media.

  • (e.g. Mycobacterium leprae - LEPROSY)
  • (e.g. Treponema pallidum - SYPHILIS)
• Exceptions to Koch's Postulates

  
  

  One infectious disease can have multiple causes/pathogens

  • (e.g. Pneumonia, meningitis and nephritis)
• Exceptions to Koch's Postulates

  
  

  One pathogen can cause several disease conditions

  • (e.g. Streptococcus pyogenes)
  • sore throat, scarlet fever, skin infections, osteomyelitis
• Exceptions to Koch's Postulates

  Ethical considerations

  • some human disease have NO animal host
  • cannot infect humans on purpose to prove the agent causes disease
  • (e.g. HIV [AIDS], Papilllomavirus [Cancer])
• Classifying Infectious Disease

  1. Patient Appearance

  • Symptoms - subjective changes in the body function
  • Signs - objective changes in body function that can be measured/observe (e.g. fever, swelling, paralysis)
  • Syndrome - specific group of symptoms and signs that may accompany a particular disease.
• Classifying Infectious Disease

  2. Spreadability

  • Communicable disease - spreads from one to another host.
  • Contagious disease - spreads easily from one person to another.
  • Noncommunicable disease - do not spread from one host to another.
• Severity or Duration

  • rate of spread of contagious/communicable disease is determined by susceptibilty of population

  Immunization/Vaccination

  • attempts to prevent spread

  Herd Immunity

  • enough immune people on the population to prevent the spread of disease
• Extent of Host Involvement

  Local Infection - microbe restricted to a particular location on the body (e.g. ABSCESS)

  Focal Infection - local infection that moves via blood or lymph to set up a new infection at another site

  Systemic Infection - spread throughout the body by blood and lymph (e.g. measles)
• Bacteremia - bacteria in blood
• Septicemia - microbes multiplying in blood
• Toxemia - toxins in blood
• Viremia - virus in blood
• Sepsis - toxic inflammatory condition arising from spread of bacteria or their toxins from infection site.
• Primary Infection - acute infection that causes the initial illness
• Secondary Infection - caused by opportunistic pathogen AFTER PRIMARY INFECTION has weakened the body's defenses.
• Subclinical (inapparent) Infection - DOES NOT cause any noticeable illness.
• Pattern of Disease

  Source of Pathogens (direct, indirect contact or by vectors) > Susceptible Host > Reservoir > Transmission > Invasion > Pathogenesis
• Predisposing Factor

  Makes the body more susceptible to a disease and may alter the course of the disease.

  Example: Gender: Female - UTI
• Development of the Disease

  I. Incubation Period

  • Specific microorganism
  • Virulence
  • No. of infecting microorganism
  • Resistance of host

  II. Prodromal Period

  • Early, mild symptoms
  • Ex: aches & malaise

  III. Period of Illness

  • most severe
  • overt signs and symptoms
  • fever, myalgia, photophobia, pharyngitis, lymphadenopathy, & GI disturbances
  • patient may die

  IV. Period of Decline

  • Signs and symptoms subside
  • Vulnerable to secondary infections

  V. Period of Convalescence

  • recovery has occured
• Transmission of Disease

  Three Principal Routes:

  • Contact - direct, indirect, droplet
  • Vehicle - airborne, water-borne, fecal-oral transmission
  • Vectors - mechanical, biological
• Vectors

  • animals that carry pathogen from one host to another.
  • arthropods (flies)
  • mechanical; biological transmission