Microbiology: Pathogens and Infection
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Questions and Answers

What is a characteristic of a commensal microorganism?

  • Lives in/on a living host without causing disease (correct)
  • Transmits microorganisms
  • Lives freely in nature
  • Causes disease

    • What is a microorganism considered as when it is able to cause disease?

  • Pathogenic (correct)
  • Commensal
  • Opportunistic
  • Saprophytic

    • What is the term for a healthy individual who possesses a microorganism and transmits it?

  • Carrier (correct)
  • Host
  • Saprophyte
  • Patient

    • Why are carriers considered serious?

    <p>Because they can communicate normally with the public and carry the organism</p> Signup and view all the answers

    What is a factor that can cause a commensal microorganism to become opportunistic?

    <p>All of the above</p> Signup and view all the answers

    What is the definition of infection?

    <p>Relation between microorganism and host</p> Signup and view all the answers

    What is the term for the destruction of host tissue by the organism due to invasion of tissue, toxin production, and other virulence factors?

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

    What type of carrier has the microorganism in their body for a short period of time?

    <p>Transient carrier</p> Signup and view all the answers

    What is the genetically determined degree of pathogenicity in microorganisms?

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

    Which of the following is NOT a type of adherence factor in bacteria?

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

    What is the function of M protein in Streptococci?

    <p>To inhibit phagocytosis</p> Signup and view all the answers

    Which of the following bacteria has fimbriae as an adherence factor?

    <p>All of the above</p> Signup and view all the answers

    What is the term for the ability of microorganisms to cause disease?

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

    Which of the following is an example of an invasive factor?

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

    What is the term for the ability of microorganisms to resist phagocytosis?

    <p>Antiphagocytic activity</p> Signup and view all the answers

    Which of the following is a type of invasive factor that helps bacteria to survive intracellularly?

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

    What is the nature of exotoxins?

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

    Which of the following is an example of a cytolysin?

    <p>Cl. perfringens</p> Signup and view all the answers

    What is the mechanism of action of A-B component toxins?

    <p>The B part binds to a specific receptor, facilitating the entry of the A part</p> Signup and view all the answers

    Which of the following bacteria can escape phagosome-lysosome fusion?

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

    What is the site of action of endotoxins?

    <p>General effect</p> Signup and view all the answers

    What is the control of production of exotoxins?

    <p>Genes on plasmids and bacteriophage</p> Signup and view all the answers

    What is the action of superantigens?

    <p>Activate a large number of T-cells, leading to a massive immune response</p> Signup and view all the answers

    Which of the following is an example of a superantigen?

    <p>Staphylococcal TSST</p> Signup and view all the answers

    Which of the following is a mechanism of action of endotoxins?

    <p>Complement C3a, C5a</p> Signup and view all the answers

    What is the composition of endotoxins?

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

    Which of the following is a characteristic of exotoxins?

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

    What is the difference between an infectious agent and a pathogen?

    <p>A pathogen is a type of infectious agent that causes disease</p> Signup and view all the answers

    What is the role of Hageman factor in endotoxin-mediated disease?

    <p>To cause Disseminated Intravascular Coagulation (DIC)</p> Signup and view all the answers

    What is a commensal?

    <p>An organism that lives on or in another organism without causing harm</p> Signup and view all the answers

    Which of the following is a step in the chain of infection?

    <p>Pathogen transmission</p> Signup and view all the answers

    What is a bacterial carrier?

    <p>An individual who is colonized with bacteria but shows no symptoms</p> Signup and view all the answers

    Study Notes

    Pathogens and Microorganisms

    • A pathogen is a microorganism that can cause disease.
    • Types of microorganisms:
      • Saprophytic: live freely in nature.
      • Parasitic: live in/on a living host.
      • Pathogenic: cause disease.
      • Commensal: live in/on a living host without causing disease.
      • Opportunistic: commensals that can cause disease under certain conditions.

    Bacterial Carrier

    • A carrier is a healthy individual who possesses microorganisms and can transmit them.
    • Types of carriers:
      • Transient: possess microorganisms for a short period (incubation period).
      • Permanent: possess microorganisms for a long period (chronic).
    • Carriers are serious because they can communicate normally and carry the organism throughout the entire epidemic period.

    Infection and Disease

    • Infection: the relationship between a microorganism and a host.
    • Disease: the destruction of host tissue by microorganisms due to:
      • Invasion of tissue.
      • Toxin production.
      • Other virulence factors.

    Factors that Govern Disease Production

    • Microbial factors:
      • Virulence: the degree of pathogenicity, determined by genes.
      • Pathogenicity: the ability to cause disease.
    • Host resistance factors:
      • Natural immunity.
      • Acquired immunity.

    Virulence Factors of Bacteria

    • Invasive factors:
      • Adherence factors (pili, fimbriae, glycocalyx).
      • Ability to invade tissues, multiply, and spread rapidly.
    • Toxin production:
      • Exotoxins: protein toxins produced by living bacteria, acting on specific cells.
      • Endotoxins: lipopolysaccharide toxins produced by dead bacteria, causing a general effect.

    Exotoxins and Endotoxins

    • Exotoxins:
      • Produced by living bacteria.
      • Act on specific cells.
      • Can be controlled by genes on plasmids and bacteriophage.
      • Examples: diphtheria toxin, cholera toxin, tetanus toxin.
    • Endotoxins:
      • Produced by dead bacteria.
      • Cause a general effect (endotoxic or septic shock).
      • Can be controlled by genes on chromosomes.
      • Examples: Gram-negative bacteria.

    Properties of Exotoxins and Endotoxins

    • Exotoxins:
      • Location of genes: plasmid, bacteriophage, PAIs.
      • Composition: proteins.
      • Action: specific.
      • Heat stability: labile, destroyed at 60°C.
      • Diffusibility: diffusible.
      • Immunogenicity: strong.
      • Toxicity: strong.
      • Convertibility to toxoid: yes.
    • Endotoxins:
      • Location of genes: bacterial chromosome.
      • Composition: lipopolysaccharide.
      • Action: non-specific.
      • Heat stability: stable at 100°C for 1 hour.
      • Diffusibility: not diffusible.
      • Immunogenicity: weak.
      • Toxicity: weak.
      • Convertibility to toxoid: no.

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    Description

    This quiz covers the basics of microbiology, including types of pathogens, bacterial carriers, infection, and disease. It also explores factors that contribute to disease production and bacterial pathogenicity.

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