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2013-10-03 13:32:44

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  1. Characteristics of a Surface infection vs Systemic infection.  Locations?
    • Surface infection: show up quickly, replicate, leave utilizing body mechanisms, typically fought by innate immunity
    • GI tract - fluid-covered mucosa and large scale fluid movements spread infection
    • Upper respiratory tract - coughing/sneezing can splatter agents onto new areas of mucosa.
    • Systemic infection: take longer to replicate, spread via lymph/blood, remain in body due to circular nature of blood, typically fought by adaptive immunity)
  2. What factors prevent surface infections from becoming systemic infections w/ specific examples and organisms?
    • 1. Temperature
    • Rhinovirus infections are restricted to upper respiratory tract (33°C) and cannot efficiently replicate in lower respiratory tract (37°C)
    • Mycobacterium leprae is limited to nasal mucosa, skin, and superficial nerves
    • 2. Site of budding
    • Influenza and parainfluenza viruses are liberated from lung epithelia by budding from the external surface, not the basal layer
  3. Describe a general outline of the stepwise invasion of different tissues of the body for systemic infection.
    • Infection: skin, throat, lung, intestine, etc
    • travel through lymph, blood to site of...
    • Multiplication: blood vessels, liver, spleen
    • travel through lymph, blood to site of...
    • Exit: skin, brain, lungs, kidney, salivary gland
  4. What defenses do microbes who have traversed the epithelium and basement membrane face in establishing a systemic infection?
    • 1. Tissue fluids containing antimicrobials (antibody, complement)
    • 2. Local macrophages (subcutaneous and submucosal)
    • 3. Physical barrier of local tissue structure
    • -viruses can spread by invasion of cells
    • -bacteria have difficulty, and often posess spreading factors (eg. streptococcal hyaluronidase)
    • 4. Lymphatic system (brings microbes to immune-heavy lymph nodes)
  5. What is the reticuloendothelial system?  What does it consist of?
    • a class of macrophage cells that occur in widely separated parts of the human body (appearance/name varies with location)
    • Kupffer cells: liver
    • Microglia: brain
    • Reticular cells: lymph nodes, bone marrow, spleen
    • Histocytes or fixed macrophages: subcutaneous tissues
    • Alveolar cells: lungs
  6. Pathogenicity vs virulence
    • Pathogenicity is a qualitative term regarding the ability to cause disease
    • eg X has pathogenicity under Y circumstances
    • Virulence is a quantitative measure of pathogenicity
    • eg X is more virulent than Y
  7. What are potential explanations for why it is difficult for Plasmodium to survive in a heterozygous cycle celled individual?
    • 1. It can't enter the deformed RBC as quickly (giving immune system more time)
    • 2. Sickled cells have shorter life span (destroying Plasmodium)
    • 3. Recent studies have shown children have enhanced immunity that increases with age
  8. What are some microbial factors that affect virulence?
    • adhesion
    • penetration
    • antiphagocytic activity
    • toxin production
    • interaction with immune system
  9. What is an attuenated pathogen?  How does it come to be?
    • A microbe with reduced pathogenicity
    • The repeated growth of a microbe in vitro leads to attenuation
    • Mycobacterium bovis took 10 years of continues growth on a potato
  10. Give 2 specific examples of rapid mutation involving a surface protein of a microbe
    • M proteins of streptococci which destroy C3 convertase thus preventing opsonization by C3B
    • Capsid proteins of picornaviruses