Microbiology Chapter 23 - Microbial Interactions with Humans

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Microbiology Chapter 23 - Microbial Interactions with Humans
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Microbiology Chapter 23 Microbial Interactions Humans
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Microbiology Chapter 23 - Microbial Interactions with Humans
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  1. Define: Adherence
    the enhanced ability of a microorganism to attach to a cell or surface
  2. Define: Attenuation
    a decrease or loss of virulence
  3. Bacteremia
    the presence of microorganisms in the blood
  4. Define: Capsule
    a dense, well-defined polysaccharide or protein layer closely surrounding a cell
  5. Define: Colonization
    the growth of a microorganism after it has gained access to host tissues
  6. Define: Dental caries
    tooth decay resulting from bacterial infection
  7. Define: Dental plaque
    bacterial cells encased in a matrix of extracellular polymers and salivary products, found on the teeth
  8. Define: Disease
    an injury to a host organism, caused by a pathogen or other factor, that affects host function
  9. Define: Endotoxin
    the lipopolysaccharide portion of the cell envelope of most gram-negative Bacteria, which is a toxin when solubilized
  10. Define: Enterotoxin
    a protein released extracellularly by a microorganism as it grows that produces immediate damage to the small intestine of the host
  11. Define: Exotoxin
    a protein released extracellularly by a microorganism as it grows that produces immediate host cell damage
  12. Define: Glycocalyx
    polymer secreted by a microorganism that coats the surface of the microorganism
  13. Define: Host
    an organism that can harbor a pathogen
  14. Define: Infection
    refers to any situation in which a microorganism is established and growing in or on a host, regardless of whether or not the host is harmed
  15. Define: Invasion
    the ability of a pathogen to enter into host cells or tissues, spread, and cause infection
  16. Define: Invasiveness
    grow in large numbers and may spread throughout host body
  17. Define: Lower respiratory tract
    the trachea, bronchi, and lungs
  18. Define: Mucous membrane
    ayer of mucus-covered epithelial cells that interact with the external environment
  19. Define: Mucus
    a liquid secretion that contains water-soluble glycoproteins and proteins that retain moisture and aid in resistance to microbial invasion on mucosal surfaces
  20. Define: Normal microflora
    microorganisms that are usually found associated with healthy body tissue
  21. Define: Opportunistic pathogen
    an organism that causes disease in the absence of normal host resistance
  22. Define: Pathogen
    an organism, usually a microorganism, that grows in or on a host and causes disease
  23. Define: Pathogenicity
    the ability of a pathogen to cause disease
  24. Define: Probiotic
    a live microorganism that, when administered to a host, may confer a health benefit
  25. Define: Septicemia
    a bloodborne systemic infection
  26. Define: Slime layer
    a diffuse layer of polymer fibers, typically polysaccharides, that forms an outer surface layer on the cell
  27. Define: Toxicity
    the ability of an organism to cause disease by means of a preformed toxin that inhibits host cell function or kills host. Also, referred to as toxigenicity
  28. Define: Toxigenicity
    toxins that inhibit host cell function or kill host cells.

    Two types: Exotoxins & Endotoxins
  29. Define: Upper respiratory tract
    the nasopharynx, oral cavity, and throat
  30. Define: Virulence
    the relative ability of a pathogen to cause disease
  31. Define: Mutualism
    both host and microbe benefit
  32. Define: Commensalism
    microbe causes no damage to host
  33. Define: Parasitism
    microbe (parasite causes damage to host)
  34. Define: Pathogenic relationship
    microbe causes damage to host (pathogen) thus, pathogen is name given to microbial parasite
  35. Define: Normal Flora
    microorganisms normally found in or on the body that typically do not cause disease
  36. Define: Synergistically
    capable of working together; two microorganisms are synergistic if they are able to produce a host response greater than the sum of the effects they produce when acting alone
  37. Define: Communicable
    able to be transmitted between hosts
  38. Define: Disease reservoir
    a natural source of disease agent. Reservoirs may include sick patients, asymptomatic carriers, animals, recovered patients, environmental sources, etc
  39. Define: Genitourinary Tract-upper
    • healthy kidney, ureters, & urinary bladder
    • free of microbes. However, distal urethra and its external opening harbour bacteria.
  40. Define: Latent Infections

    Give an example(s)
    An infection that goes from being symptomatic to asymptomatic. Later they reappear as symptomatic.

    Examples: Cold sores (Herpes virus infections) and shingles (Herpes varicella): person who had chickenpox as child still harbors virus. Later in adulthood, the individual develops shingles.
  41. Characterise the difference between Primary (1o versus Secondary (2o) Infection

    Give an example
    An infection caused by one pathogen (1o) is followed by a 2o infection caused by second pathogen.

    Ex: Mild respiratory caused by virus may be followed by bacterial pneumonia.
  42. Asymptomatic Diseases (aka _______) means what?
    Give an example
    Asymptomatic Diseases (aka subclinical)   mean that the patient is unaware of the disease because they do not present symptoms

    Carriers: person colonized but does not have disease: Mary Mallon
  43. Inanimate objects capable of transmitting microbe are called _____.

    Give examples
    Inanimate objects capable of transmitting microbe are called Fomtie

    Ex: Hospital equipment; patient’s bedding and gowns; latex gloves; eating and drinking utensils
  44. Organisms that live on or in a host organism, causing damage to the host, are called ______. Microbial parasites are called _______.
    Organisms that live on or in a host organism, causing damage to the host, are called parasites. Microbial parasites are called pathogens
  45. What does the outcome of a host-parasite relationship depend on?
    The outcome of a host-parasite relationship depends on the pathogenicity (virulence) of the parasite; that is, on the ability of the parasite to cause damage on the host, and on the resistance or susceptibility of the host to the parasite

    *(virulence = degree of pathogenicity)
  46. True of False: The host-parasite relationship is static
    False

    The host-parasite relationship is dynamic and the virulence of the pathogen and the resistance of the host are constantly changing
  47. What is the causative agent of Strep Throat?
    Streptococcus pyogenes is the causative agent of Strep Throat; is considered a pathogen.
  48. Candida albicans is normally what type of bacteria?
    Candida albicans is normally a commensal bacteria (causes no damage to host). But, if host defense mechanisms are weakened, it becomes an opportunistic pathogen. (Ex. Thrush in children)
  49. Neisseria meningitidis often resides benignly where? Where can it be pathogenic?
    Neisseria meningitidis often resides benignly in respiratory tract but can cause meningitis in brain and spinal cord.
  50. Streptococcus pneumoniae normally resides where?
    Streptococcus pneumoniae is a normal resident of the nose and throat. Can cause pneumonia in the lungs

    We now immunize the elderly against it
  51. True or False: "Infection" is synonymous with "disease"
    Infection is not synonymous with disease; even though the public and even physicians often use the terms synonymously.
  52. True of False: The normal flora of the human body can never cause disease, only new bacteria can cause disease
    False

    Normal flora can sometimes cause disease if the host resistance is compromised
  53. What are the 6 Steps to Disease
    Exposure and Entry:

    • I. Portals of Entry
    • II. Adherence
    • III. Invasion
    • IV. Colonization & Growth
    • V. Virulence factors produce damage 
    •      A. Toxins
    •      B. Invasive factors
    • VI. Disease
  54. How do most microbes enter the human body?
    Most microbes enter through breaks or wounds in skin or invasion of mucous membranes of respiratory, digestive, or genitourinary tract
  55. How do bacteria or viruses usually initiate infection?
    Bacteria or viruses usually initiate infection by adhering specifically to epithelial cells through interactions between macromolecules on surfaces of the pathogen and host.
  56. Where do infections often begin?
    Infections often begin at sites in mucous membranes, which consist of single or multilayers of epithelial cells, tightly packed cells that interface with environment
  57. Define: Host Selectivity
    a microorganism that normally infects humans binds to human epithelial cells better than those of a rat
  58. What structures of a bacteria may be involved with adherence?
    • Capsules (well defined layer), glycocalyx, or slime layers (loose network of polymer fibers) may be involved in adherence. (also resist phagocytosis).
    • Fimbriae & Pili are bacterial surface protein structures that also function in attachment (bind host cell glycoproteins)
  59. When does Disease result?
    Disease results when anatomical and/or physiological damage occurs due to Virulence of microbe
  60. Humoral Immunity is mediated by _____, whereas Cellular Immunity is mediated by _____
    Humoral Immunity is mediated by antibodies, whereas Cellular Immunity is mediated by cells (T cells)
  61. Describe the secreted enzyme, Hyaluronidase
    Hyaluronidase is also called the spreading factor because it catalyzes the breakdown of hyaluronic acid, the substance that cements the human cells in tissues together. This allows the bacterial cells to spread through tissue causing a condition known as cellulitis. [Staphyloccus,Streptococcus,Clostridia]
  62. Describe the secreted enzyme, Coagulase
    This enzyme catalyzes the conversion of fibrinogen to fibrin with resultant clot formation. Present in pathogenic Staphyloccus. (clot prevents them being phagocytized.
  63. Describe the secreted enzyme, Fibrinolysin
    This catalyzes the conversion of plasminogen to the fibrinolytic enzyme plasmin. Thus it acts opposite of coagulase. In Staphylococcus aureus, the gene for fibrinolysin is on a bacteriophage and is expressed during lysogeny.
  64. Describe the secreted enzyme, Lipase
    Production of excessive amounts of lipase allow bacteria to penetrate fatty tissue with the consequent formation of abscesses.
  65. Describe the secreted enzyme, Collagenase
    This enzyme catalyzes the degradation of collagen, a protein found in tendons, ligaments, cartilage, nails and hair.
  66. Describe the enzyme, Leukocidins
    cause lysis of white blood cells; Staphyloccus aureus (pyogenic: pus producing).

    Streptokinase and Streptodornase: actually fibrinolytic enzymes
  67. Describe the enzyme, Lecithinase
    destroys red blood cells & other tissue cells.
  68. Describe the enzyme, Hemolysins
    lyse red blood cells
  69. What are the three general types of Exotoxins?
    • Cytolytic toxins (include hemolysins): damage cell membranes, causing cell lysis & death (also are cytotoxins).
    • A-B toxins: B promotes specific binding of toxin to host cell receptor (allows transfer of A (toxic part) across targeted cell membrane).
    • Superantigen toxins: Stimulate large numbers of immune lymphocytes and causes systemic as well as inflammatory responses. Extensive inflammation & tissue damage.
  70. What is the LD50? What bacterial characteristic(s) can you estimate from it?
    • The LD50 (Lethal Dose 50) is the dose of an agent that kills 50% of the animals in a test group
    • The virulence of a pathogen can be estimated from experimental studies of the LD50
  71. What do Cytotoxins cause?
    Inhibit a cell function or cause cell death 

    Corynebacterium diptheriae

    Cytolysins (Cytolytic toxins) are cytotoxins that cause cell death by lysis): Ex alpha toxin of Staph.
  72. What do Neurotoxins cause?
    inhibit nerve transmission
  73. What do Enterotoxins cause?
    alter permeability of intestinal epithelium

    Examples: Cholera and Staph aureus food poisoning enterotoxin (also superantigen)
  74. What type of toxin is Diptheria?
    Diptheria toxin is an A-B toxin that inhibits a cell function: protein synthesis
  75. Describe what Diptheria does (in detail)? How much of this toxin is needed to kill a cell? How is it formed?
    • 1. B promotes binding of toxin to cell membrane
    • 2. When it binds to cell membrane, it is cleaved and A is internalized.
    • 3. A catalyzes ADP-ribosylation of elongation factor 2 (EF-2) and it no longer aids the transfer of amino acids to growing polypeptide chain. Ends protein synthesis
  76. How much of Diptheria is needed to kill a cell? How is it formed?
    Only a single toxin molecule is needed to kill a cell.
  77. How is Diptheria formed?
    Diptheria toxin is formed only by strains of Corynebacterium diptheriae cells that are lysogenized by phage beta.

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