Bmsc210 Final p4

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  1. Normal microbial flora
    • – Microorganisms usually found associated with human body tissue
    • - Humans are colonized by microorganisms at birth
  2. Generally speaking does skin support growth of most micro organisms? Why?
    -The skin is generally a dry, acid environment that does not support the growth of most microorganisms
  3. Moist areas (e.g., sweat glands) are readily colonized by gram-___ bacteria and other normal flora of the skin
  4. Composition of micro flora is influenced by:
    • • Environmental factors (e.g., weather)
    • • Host factors (e.g., age, personal hygiene
  5. The tooth consists of a ___ ___ surrounding __ ___.
    mineral matrix (enamel)

    living tissue (dentin and pulp)
  6. Saliva contains ___ ___, But high concentrations of ___ near surfaces in the mouth promote localized microbial growth
    • antimicrobial enzymes
    • nutrients
  7. Bacteria colonize tooth surfaces by first:
    attaching to acidic glycoproteins deposited there by saliva
  8. Extensive growth of oral microorganisms, especially ___, results in a thick bacterial layer known as ___
    • streptococci
    • dental plaque
  9. As dental plaque continues to develop, ___ bacterial species begin to grow
  10. How are dental Caries formed
    As dental plaque accumulates, the microorganisms produce high concentrations of acid that results in decalcification of the tooth enamel (dental caries)
  11. What Bacteria are common agents in dental caries?
    The lactic acid bacteria Streptococcus sobrinus and Streptococcus mutans
  12. The human gastrointestinal (GI) tract consists of:
    -Is responsible for:
    -contains __ to __ microbial cells
    :stomach, small intestine, and large intestine

    -digestion of food, absorption ofnutrients, and production of nutrients by theindigenous microbial flora

    -1013 to 1014
  13. Microbial populations in different areas of the GI tract are influenced by ___ and ________
    • diet
    • the physical conditions in the area
  14. What prevents many organisms from colonizing the  GI tract
    The acidity of the stomach and the duodenum of the small intestine (~pH 2)
  15. different compounds produced by microflora (depending on composition of the intestinal flora and the diet) include:
    • – Vitamins
    • – Gas, organic acids, and odor
    • – Enzymes
  16. A restricted group of organisms colonizes the upper respiratory tract (sinuses, nasopharynx, pharynx. oral cavity, larynx)
    (4 examples)
    • staphylococci,
    • streptococci,
    • diphtheroid bacilli,
    • gram-negative cocci
  17. The lower respiratory tract (lungs trachea, bronchi) ___ microflora in healthy individuals
  18. The bladder is typically ___ in both males and females
  19. Altered conditions (such as ____ ) can cause potential pathogens in the urethra (such as ___ ___ and ___ ___) to multiply and become pathogenic
    • change in pH
    • Escherichia coli and Proteus mirabilis
  20. The vagina of the adult female is weakly ___ic and contains significant amounts of ___
    • acidic
    • glycogen
  21. Lactobacillus acidophilus
    a resident organism in the vagina, ferments glycogen, producing lactic acid maintaining acidic environment
  22. Pathogens
    Microbial parasites
  23. Pathogenicity
    – The ability of a parasite to inflict damage on the host
  24. Virulence
    the relative ability of a pathogen to cause disease
  25. Opportunistic pathogen
    – Causes disease only in the absence of normal host resistance
  26. Infection
    – Situation in which a microorganism is established and growing in a host, whether or not the host is harmed
  27. Disease
    – Damage or injury to the host that impairs host function
  28. 6 steps of pathogenic infection
    EXPOSURE to pathogens

    ADHERENCE to skin or mucosa

    INVASION through epithelium

    COLONIZATION and GROWTH: Production of virulence factors

    • TOXICITY: toxin effects are local or systemic
    • or
    • INVASIVENESS: further growth at original and distant sites

  29. Virulence can be estimated from:
    • studies of the LD50 (lethal dose50)
    • -The amount of an agent that kills 50% of the animals in a test group
  30. Highly virulent pathogens show a ___ difference in the number of cells required to kill 100% of the population as compared to 50% of the population
  31. Organism Toxicity
    – Organism causes disease by means of a toxin that inhibits host cell function or kills host cells
  32. ___ can travel to sites within host not inhabited by pathogen to do damage
  33. Invasiveness
    • – Ability of a pathogen to grow in host tissue at densities that inhibit host function
    • - Can cause damage without producing a toxin
  34. Many pathogens use a combination of ___, ___ and other virulence factors to enhance pathogenicity
    • toxins
    • invasiveness
  35. Pathogens may spread throughout the host via the ___ or ___ systems
    • circulatory
    • lymphatic
  36. Bacteria and viruses that initiate infection often adhere specifically to ___ cells through macromolecular interactions on the surfaces of the pathogen and the host cell
  37. Bacterial adherence can be facilitated by:
    • – Extracellular macromolecules that are not covalently attached to the bacterial cell surface
    • • Examples: slime layer, capsule

    – Fimbriae and pili
  38. Pathogens produce enzymes that:
    (2 functions with an example)
    • – Enhance virulence by breaking down or altering host tissue to provide access to nutrients
    • Example: hyaluronidase

    • – Protect the pathogen by interfering with normal host defense mechanisms
    • Example: coagulase
  39. Exotoxins
    • – Proteins released from the pathogen cell as it grows
    • – Three categories:
    • • Cytolytic toxins
    • • AB toxins
    • • Superantigen toxins
  40. -Staphylococcal α-toxin kills nucleated cells and lyses erythrocytes(red blood cells) by:
    creating α-toxin pore in membrane
  41. hemolysins
    Toxins that lyse red blood cells
  42. Cytolytic toxins
    – Work by degrading cytoplasmic membrane integrity, causing cell lysis and death
  43. AB toxins
    (3 examples)
    • – Consist of two subunits, A and B
    • – Work by binding to host cell receptor (B subunit) and transferring damaging agent (A subunit) across the cell membrane
    • • Examples: diphtheria toxin, tetanus toxin, botulinum toxin
  44. Diptheria toxin
    toxin type
    • -AB toxin
    • -causes the disease diphtheria in humans by gaining entry into the cell cytoplasm and inhibiting protein synthesis
    • -catalyzes the transfer of NAD+ to a diphthamide residue in eukaryotic elongation factor-2 (EF2), inactivating this protein.
    • -this blocking transfer of an amino acid from a tRNA to the growing polypeptide chain
  45. Super antigen toxin
    • -bear antigens which cause non-specific activation of T-cells
    • -up to 25% of all T cells avtivated in non specific way is counterproductive
  46. Clostridium tetani and Clostridium botulinum
    produce potent AB exotoxins that affect nervous tissue
  47. Botulinum toxin
    • -consists of several related AB toxins that are the most potent biological toxins known
    • -Blocks acetylcholine (induces contraction) being sent to muscles from nervous system resulting in flaccid paralysis.
  48. tetanus toxin
    • -also an AB protein neurotoxin
    • -Glycine (inhibits acetylcholine- muscle contraction) release is blocked resulting in spastic paralysis.(permanent contraction)
  49. Enterotoxins
    • – Exotoxins whose activity affects the small intestine
    • – Generally cause massive secretion of fluid into the intestinal lumen, resulting in vomiting and diarrhea
    • • Example: cholera toxin
  50. Cholera toxin
    (produced by)
    (mechanism:5 points)
    -Produced by Vibrio cholerae

    • -cholera toxin in AB form binds to GM1 gangliosides
    • -Once bound, the A subunit is endocytosed by the cell
    • -adenylate cyclase activity is increased creating cyclic AMP
    • -Na+ movement blocked from leaving lumen, Cl- and HCO3-(bicarbonate) secretion into lumen
    • -massive secretion of H2O into lumen giving diarrhea symptoms
  51. Endotoxin
    • – The lipopolysaccharide portion of the cell envelope of certain gram-negative Bacteria, which is a toxin when solubilized
    • -induce cytokines- fever
    • – Generally less toxic than exotoxins
    • – The presence of endotoxin can be detected by the Limulus amoebocyte lysate (LAL) assay
    • .
  52. -The lipid A portion of LPS is responsible for ___, and the polysaccharide fraction makes the complex water-soluble and ___
    • toxicity
    • immunogenic
  53. Salmonella
    A Plethora of Virulence Factors
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Bmsc210 Final p4
Bmsc210 Final p4
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