Microbial Mechanisms of Pathogenicity
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Questions and Answers

What is the primary mechanism by which aspirin and acetaminophen reduce fever?

  • Block prostaglandin formation (correct)
  • Inhibit the release of endorphins
  • Enhance the effects of cortisol
  • Increase white blood cell production

    • What is the primary cause of septic shock?

  • Viral infection
  • Parasite infection
  • Fungal infection
  • Bacterial infection (correct)

    • What effect does tumor necrosis factor (TNF) have in cases of endotoxic shock?

  • It promotes the formation of effective antitoxins
  • It damages capillaries and reduces blood pressure (correct)
  • It strengthens capillaries
  • It allows fluid retention

    • What is the role of amebocytes in the Limulus amebocyte lysate (LAL) test?

    <p>Identifying the presence of endotoxins</p> Signup and view all the answers

    Which type of bacteria is specifically known to cause endotoxic shock?

    <p>Gram-negative bacteria</p> Signup and view all the answers

    What are superantigens primarily known to stimulate in the immune system?

    <p>Proliferation of T cells</p> Signup and view all the answers

    Which component is identified as the endotoxin in Gram (-) bacteria?

    <p>Lipid A of LPS</p> Signup and view all the answers

    What is a common symptom associated with the release of superantigens?

    <p>Nausea and diarrhea</p> Signup and view all the answers

    Which of the following statements about endotoxins is accurate?

    <p>They can cause immediate worsening of symptoms when antibiotics are administered.</p> Signup and view all the answers

    What can the excessive release of cytokines from macrophages due to endotoxins lead to?

    <p>Tissue death and shock</p> Signup and view all the answers

    What complication can arise from blood clotting induced by endotoxins?

    <p>Obstruction of capillaries</p> Signup and view all the answers

    Which of the following pathogens is known to secrete toxins that can lyse phagolysosome and plasma membranes?

    <p>Trypanosoma cruzi</p> Signup and view all the answers

    Which symptom is NOT typically associated with endotoxin release?

    <p>Localized rash</p> Signup and view all the answers

    What are adhesins primarily responsible for in microbial interactions?

    <p>Promoting attachment to host cells</p> Signup and view all the answers

    Which of the following microbes is associated with having a glycocalyx?

    <p>Streptococcus mutans</p> Signup and view all the answers

    How do capsules enhance the virulence of bacterial pathogens?

    <p>By resisting phagocytosis</p> Signup and view all the answers

    What mechanism do Shigella species use to penetrate host defenses?

    <p>Endocytosis via receptor-mediated pathways</p> Signup and view all the answers

    What is the role of actin polymerization in Shigella dysenteriae infection?

    <p>To promote bacterial movement between cells</p> Signup and view all the answers

    Which of these microbes is known to form capsules that resist phagocytosis?

    <p>Streptococcus pneumoniae</p> Signup and view all the answers

    What is a consequence of dysentery caused by bacterial infection?

    <p>Damage to the intestinal wall</p> Signup and view all the answers

    What cellular structures can serve as adhesins for bacteria?

    <p>Pili and fimbriae</p> Signup and view all the answers

    What term describes the ability of a microorganism to cause disease by overcoming host defenses?

    <p>Pathogenicity</p> Signup and view all the answers

    Why might a pathogen not cause disease if it gains access to the host by an inappropriate route?

    <p>Pathogens require specific entry routes to infect.</p> Signup and view all the answers

    What does ID50 represent in microbiology?

    <p>The infectious dose for 50% of the population</p> Signup and view all the answers

    What is the LD50 for botulinum toxin in mice?

    <p>0.03 ng/kg</p> Signup and view all the answers

    What is a common characteristic of adhesins that facilitate the attachment between pathogens and hosts?

    <p>They are usually glycoproteins or lipoproteins.</p> Signup and view all the answers

    Which of the following microorganisms can cause disease through more than one portal of entry?

    <p>Bacillus anthracis</p> Signup and view all the answers

    What does an increased number of invading microbes imply?

    <p>Increased likelihood of disease.</p> Signup and view all the answers

    What is the infectious dose for Bacillus anthracis via the skin?

    <p>10-50 endospores</p> Signup and view all the answers

    What is typically true about the virulence of a microbe?

    <p>Virulence can be expressed as ID50.</p> Signup and view all the answers

    What is the role of siderophores in pathogen survival?

    <p>To bind iron and transport it into the microbial cell</p> Signup and view all the answers

    Which of the following is true about exotoxins?

    <p>They work by destroying host cell parts or inhibiting metabolic functions</p> Signup and view all the answers

    What is meant by toxemia?

    <p>Presence of toxins in the blood</p> Signup and view all the answers

    How do pathogens release toxins when iron levels are low?

    <p>By increasing toxin production to induce host cell death</p> Signup and view all the answers

    How does the body respond to the presence of exotoxins?

    <p>By generating antibodies known as antitoxins</p> Signup and view all the answers

    What defines intoxications?

    <p>Caused by the presence of toxins only</p> Signup and view all the answers

    Which statement about the genetics of exotoxins is correct?

    <p>Most exotoxin genes are carried on plasmids or phages</p> Signup and view all the answers

    What can happen to exotoxins when they are inactivated?

    <p>They can still stimulate the production of antitoxins</p> Signup and view all the answers

    What is a common consequence of host cell rupture due to pathogens?

    <p>Release of pathogens to infect other tissues</p> Signup and view all the answers

    What is the primary function of bacterial siderophores?

    <p>To bind and transport iron from the host</p> Signup and view all the answers

    Which bacterial pathogen utilizes fimbriae and outer membrane proteins for cell attachment?

    <p>Neisseria gonorrhoeae</p> Signup and view all the answers

    What is the primary function of coagulases produced by bacterial pathogens?

    <p>Clot fibrinogen in blood</p> Signup and view all the answers

    Which enzyme is produced by pathogens like Clostridium perfringens that breaks down connective tissue?

    <p>Hyaluronidase</p> Signup and view all the answers

    Which of the following pathogens is known for its antigenic variation to evade host immunity?

    <p>Trypanosoma brucei</p> Signup and view all the answers

    What role does the M protein of Streptococcus pyogenes play in its pathogenicity?

    <p>Mediates attachment and resists phagocytosis</p> Signup and view all the answers

    Which extracellular enzyme produced by Neisseria specifically targets immunoglobulin A?

    <p>IgA protease</p> Signup and view all the answers

    How do mycolic acids contribute to the virulence of Mycobacterium tuberculosis?

    <p>They allow growth within phagocytes</p> Signup and view all the answers

    Which pathogen is associated with the production of streptokinase, an enzyme that breaks down blood clots?

    <p>Streptococcus pyogenes</p> Signup and view all the answers

    What mechanism allows pathogens to manipulate the host's cell cytoskeleton?

    <p>Facilitation of pathogen uptake</p> Signup and view all the answers

    Which component produced by Streptococcus pyogenes helps protect it from phagocytosis?

    <p>M protein</p> Signup and view all the answers

    Study Notes

    Microbial Mechanisms of Pathogenicity

    • Pathogenicity is the microorganism's ability to cause disease by overcoming host defenses.
    • Virulence is the degree of pathogenicity.
    • To cause disease, pathogens must:
      • Gain access to the host.
      • Adhere to target tissues.
      • Penetrate or evade host defenses.
      • Damage host tissues (direct or indirect).

    Portals of Entry

    • Mucous membranes in the respiratory, GI, and genitourinary tracts and conjunctiva.
    • Skin
    • Parenteral route (deposition directly into tissues beneath the skin or mucous membranes when barriers are compromised).

    Pathogen Numbers and Virulence

    • The more microbes that gain access to the host, the increased likelihood of disease.
    • Virulence can be measured by the infectious dose (ID50), which is the dose infecting 50% of a population.
    • Examples:
      • Bacillus anthracis (Skin: ID50 = 10-50 endospores, Respiratory: ID50 = 10,000-20,000 endospores, GI: 250,000 to 1,000,000 endospores).

    Adherence

    • Adherence is the attachment between pathogen and host.
    • Adhesins (ligands) on the pathogen bind to complementary receptors on host cells.
    • Adhesins can be found on glycocalyx, pili, fimbriae, and flagella.

    How Bacterial Pathogens Penetrate Host Defenses

    • Capsules: Capsules resist phagocytosis by preventing attachment.
    • Cell wall components: Some components like M protein in Streptococcus pyogenes make the microbe resistant to phagocytosis. Other elements like Opa in Neisseria gonorrhoeae help attachment to host cells. M. tuberculosis has mycolic acids preventing phagocytosis.
    • Extracellular enzymes: Coagulases clot fibrinogen, kinases break down fibrin, hyaluronidase hydrolyzes hyaluronic acid, collagenase breaks down collagen, and IgA proteases degrade IgA.
    • Antigenic variation: Some pathogens (like Neisseria gonorrhoeae and Trypanosoma brucei) can change their surface antigens, making them harder to identify and fight by the immune system.

    How Bacterial Pathogens Damage Host Cells

    • Host's nutrient use
    • Direct damage in the vicinity of invasion
    • Toxin production

    Using the Host's Nutrients

    • Siderophores (proteins secreted by some pathogens) bind iron.
    • Iron is essential for the growth of pathogens.

    Toxin Vocabulary and Types

    • Toxins: poisonous substances produced by microbes.

    • Toxigenicity: the ability of microbes to produce toxins.

    • Toxemia: toxins in the blood.

    • Intoxication: caused by toxins, not microbial growth.

    • Exotoxins: proteins produced inside pathogenic bacteria (secreted or released following lysis). Exotoxins damage host cells or inhibit their metabolic functions or are involved in other cellular actions such as cell death.

      • A-B exotoxins: consist of two parts (A and B). B is the binding component and A is the active/enzymatic component responsible for the toxic action.
      • Membrane-disrupting toxins: disrupt the phospholipid bilayer, cause lysis of host cells, and have cytotoxic effects. (Examples: Leukocidins and Hemolysins).
      • Superantigens: bacterial antigens that cause a very strong immune response.

    • Endotoxins: lipid portions of lipopolysaccharides (LPS) part of the outer membrane of the gram-negative cell wall released during bacterial multiplication/cell death.

    Portals of Exit

    • Usually the same portals as entry (respiratory, GI, genitourinary tracts, skin, wounds, biting insects).

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    Related Documents

    Microbial Mechanisms of Pathogenicity PDF

    Description

    This quiz explores the mechanisms underlying microbial pathogenicity and virulence. It covers the various portals of entry pathogens use to invade hosts, the significance of pathogen numbers, and the concept of infectious dose. Test your knowledge on how microbes adhere and evade host defenses.

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