Microbial Virulence Factors and Pathogenesis
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Questions and Answers

Opportunistic pathogens frequently cause disease in immunocompetent individuals.

False

What does the term LD50 refer to?

  • The number of organisms required to kill half the hosts. (correct)
  • The number of organisms required to cause infection in half the hosts.
  • The number of organisms required to cure half the hosts.
  • The number of organisms required to cause disease in all hosts.

    • Which of the following is not a stage of bacterial pathogenesis?

  • Transmission
  • Adherence to mucous membranes
  • Production of antibodies (correct)
  • Evasion of host defenses

    • What are the two main types of inflammation caused by bacterial infection?

    <p>Pyogenic inflammation and granulomatous inflammation</p> Signup and view all the answers

    What is the term for human diseases where animals are the reservoir?

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

    What is the primary mechanism by which bacteria adhere to human cells?

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

    Coagulase is an enzyme that degrades hyaluronic acid in the subcutaneous tissue.

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

    What is the process by which bacteria can evade host defenses by living within cells?

    <p>Intracellular survival</p> Signup and view all the answers

    Which of the following is not a mechanism used by bacteria to survive and grow intracellularly?

    <p>Production of toxins</p> Signup and view all the answers

    Which of the following is not a feature of exotoxins?

    <p>Stable at high temperatures, such as 100°C for 1 hour</p> Signup and view all the answers

    What is the main mechanism by which bacteria cause disease, besides the production of toxins?

    <p>Invasion of tissues</p> Signup and view all the answers

    Immunopathogenesis refers to the direct damaging effects of bacteria on host tissues.

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

    What is the term for the time period between exposure to a pathogen and the appearance of symptoms?

    <p>Incubation period</p> Signup and view all the answers

    What is the term for the period during which nonspecific symptoms occur, before the characteristic features of the disease appear?

    <p>Prodrome period</p> Signup and view all the answers

    What is the term for the period during which an individual remains asymptomatic despite being infected with a pathogen?

    <p>Subclinical infection</p> Signup and view all the answers

    What is the term for individuals who continue to harbor a pathogen after recovering from an infection, potentially shedding the pathogen without exhibiting symptoms?

    <p>Chronic carriers</p> Signup and view all the answers

    Latent infections are characterized by persistent symptoms that can recur after periods of remission.

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

    Study Notes

    Microbial Virulence Factors and Pathogenesis

    • A microorganism is a pathogen if it can cause disease. Some are highly pathogenic, causing disease often, while others cause it rarely.
    • Opportunistic pathogens rarely cause disease in healthy individuals but can cause serious infection in immunocompromised people.
    • Virulence is a measure of pathogenicity, quantified by the number of organisms needed to cause disease (LD50 – 50% lethal dose) or infection (ID50 – 50% infectious dose). A lower LD50/ID50 indicates higher virulence.

    Stages of Bacterial Pathogenesis

    • Most bacterial infections originate from external sources, but some are caused by normal flora.
    • Transmission occurs by several routes (e.g. human to human, animal to human).
    • Infection involves several stages
      • Entry into the body
      • Evading the host's primary defenses (skin, stomach acid)
      • Adherence to mucous membranes (usually by pili)
      • Colonization by growth at the site of adherence
      • Disease symptoms caused by toxin production or invasion.
      • Host response with inflammation.
      • Progression or resolution of the disease.

    Determinants of Bacterial Pathogenesis

    • Transmission: Microbes can spread through direct contact, vectors (e.g., insects), or indirect contact (e.g., contaminated food, water, or soil).
    • Adherence to Cell Surfaces: Pili or glycocalyx facilitate attachment to host cells or surfaces.
    • Invasion, Inflammation, and Intracellular Survival: Bacteria may invade tissue, trigger inflammation (pyogenic or granulomatous), or survive within host cells to evade immune responses. This survival can be aided by a variety of factors such as inhibiting lysosome-phagosome fusion or inhibiting acidification.

    Toxin Production

    • Toxins are another key virulence factor that causes disease.
    • Exotoxins and endotoxins are different in their source, chemical composition, and toxicity. Exotoxins are protein-based molecules produced and secreted by bacteria. Endotoxins are part of the cell wall of certain gram-negative bacteria.

    Immunopathogenesis

    • In some diseases, the immune response to the organism, not the organism itself, causes the symptoms.
      • (e.g, antibodies against the M protein of Streptococcus pyogenes cross-react with tissues, causing arthritis, carditis and chorea in rheumatic fever)

    Typical Stages of an Infectious Disease

    • Incubation period: Time between exposure and symptom onset
    • Prodrome period: Time of nonspecific symptoms
    • Specific-illness period: Characteristic symptoms appear
    • Recovery period (convalescence): Symptoms resolve and health returns
    • Subclinical infections: individual infected but asymptomatic. Antibody presence indicates a prior infection.

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    Related Documents

    Microbial Virulence Factors And Pathogenesis Of Bacterial Infection PDF

    Description

    Explore the factors that determine microbial virulence and the stages involved in bacterial pathogenesis. Learn how pathogens cause disease, the concept of opportunistic pathogens, and the various routes of transmission. This quiz will test your understanding of these critical concepts in microbiology.

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