Chapter 15: Microbial Mechanisms of Pathogenicity Quiz
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Questions and Answers

What is the defining characteristic that distinguishes pathogenicity from virulence?

  • Pathogenicity is the ability of a microbe to enter a host, while virulence is the ability to evade the host's immune system.
  • Pathogenicity is a qualitative measure, while virulence is a quantitative measure of a pathogen's ability to cause disease.
  • Pathogenicity refers to the overall potential to cause disease, while virulence describes the specific mechanisms used to cause harm.
  • Pathogenicity is the ability to cause disease, while virulence is the severity of the disease caused. (correct)

    • Which of the following is NOT considered a typical virulence factor for microbes?

  • Capsules
  • Nutrient acquisition mechanisms (correct)
  • Toxins
  • Antigenic variation

    • A pathogen with a low ID$_{50}$ value is considered to have which of the following properties?

  • High infectiousness (correct)
  • High virulence
  • Low infectiousness
  • Low virulence

    • Which of the following is the preferred portal of entry for the development of anthrax disease caused by $Bacillus$ $anthracis$?

    <p>Parenteral route</p> Signup and view all the answers

    How does the concept of virulence differ from the concept of pathogenicity?

    <p>Virulence describes the specific mechanisms used by a microbe to cause harm, while pathogenicity is a measure of the overall potential to cause disease.</p> Signup and view all the answers

    Which of the following is NOT considered a typical portal of entry for microbial pathogens?

    <p>Digestive system</p> Signup and view all the answers

    What is the primary difference between pathogenicity and virulence in the context of microbial infections?

    <p>Pathogenicity refers to the overall potential to cause disease, while virulence describes the specific mechanisms used to cause harm.</p> Signup and view all the answers

    Which of the following is NOT considered a typical virulence factor for microbial pathogens?

    <p>Nutrient acquisition</p> Signup and view all the answers

    How does the ID$_{50}$ value relate to the infectiousness of a microbial pathogen?

    <p>Pathogens with a low ID$_{50}$ value have high infectiousness.</p> Signup and view all the answers

    Which of the following is the preferred portal of entry for the development of anthrax disease caused by $Bacillus$ $anthracis$?

    <p>Parenteral route</p> Signup and view all the answers

    What is the primary function of hyaluronidase in the context of pathogen virulence?

    <p>To break down hyaluronic acid in connective tissue</p> Signup and view all the answers

    What is the primary function of IgA protease in the context of pathogen virulence?

    <p>To destroy IgA antibodies in the mucosa</p> Signup and view all the answers

    Which of the following is NOT a key virulence factor related to a pathogen's ability to survive inside phagocytes?

    <p>Breaking down hyaluronic acid in connective tissue</p> Signup and view all the answers

    What is the primary function of antigenic variation in the context of pathogen virulence?

    <p>To change the pathogen's surface antigens through genetic mutations/recombination</p> Signup and view all the answers

    What is the primary function of toxigenicity in the context of pathogen virulence?

    <p>To produce a poisonous substance (toxin) that acts as an antigen</p> Signup and view all the answers

    What is the primary function of toxoid in the context of pathogen virulence?

    <p>To chemically modify a toxin so that it is no longer toxic</p> Signup and view all the answers

    What is the primary function of antitoxin in the context of pathogen virulence?

    <p>To provide antibodies against a toxin, not the pathogen itself</p> Signup and view all the answers

    What is the primary function of toxemia in the context of pathogen virulence?

    <p>The presence of a toxin in the bloodstream</p> Signup and view all the answers

    What is the primary function of exotoxins and endotoxins in the context of pathogen virulence?

    <p>Different types of toxins produced by some bacteria</p> Signup and view all the answers

    What is the primary mechanism by which some bacteria can produce toxins as a virulence factor?

    <p>Through bacterial plasmids that carry genes for toxins</p> Signup and view all the answers

    Which term refers to the amount of toxin required to kill 50% of a population?

    <p>LD50</p> Signup and view all the answers

    Which of the following statements about LD50 and lethality is correct?

    <p>Pathogens with a low LD50 have high lethality.</p> Signup and view all the answers

    Which of the following is an example of a bacterial adhesin?

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

    What is the function of coagulase, a bacterial enzyme?

    <p>It helps form blood clots, preventing host defenses from reaching the bacterium.</p> Signup and view all the answers

    Which bacterial structure is responsible for the adhesion of Streptococcus mutans?

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

    Which of the following pathogens uses hooks as adhesins?

    <p>Treponema pallidum</p> Signup and view all the answers

    What is the function of kinase, a bacterial enzyme?

    <p>It breaks down blood clots surrounding the bacterium, allowing it to spread.</p> Signup and view all the answers

    Which bacterial structure is responsible for the adhesion of Escherichia coli O157:H7?

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

    Which bacterial structure is responsible for the adhesion of Streptococcus pyogenes?

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

    Which bacterial structure is responsible for the adhesion of Neisseria gonorrhoeae?

    <p>Opa proteins</p> Signup and view all the answers

    What is the primary mechanism of action for Type II exotoxins?

    <p>Disrupting the host cell membrane by forming channels or disrupting the phospholipid component</p> Signup and view all the answers

    Which type of exotoxin is considered the most common?

    <p>Type III A-B Toxins</p> Signup and view all the answers

    What is the primary difference between exotoxins and endotoxins in terms of fever production?

    <p>Exotoxins can cause fever, while endotoxins cannot</p> Signup and view all the answers

    How are exotoxins and endotoxins typically neutralized?

    <p>Exotoxins are neutralized by antitoxin antibodies, while endotoxins are not</p> Signup and view all the answers

    What is the relationship between immunogens and antigens?

    <p>Immunogens are a type of antigen that stimulate a strong immune response</p> Signup and view all the answers

    What is the primary pathogenic property of parasitic protozoa?

    <p>Feeding on host tissue and damaging the intestinal lining</p> Signup and view all the answers

    How do parasitic protozoa typically avoid the host's immune defenses?

    <p>By growing within phagocytic cells and undergoing antigenic variation</p> Signup and view all the answers

    What is the primary pathogenic property of parasitic helminths (worms)?

    <p>They feed on the host's tissues and nutrients without killing the host</p> Signup and view all the answers

    Which of the following is a key difference between exotoxins and endotoxins in terms of their structural composition?

    <p>Exotoxins are composed of proteins, while endotoxins are composed of lipids</p> Signup and view all the answers

    What is the primary portal of exit for pathogens leaving the host?

    <p>The gastrointestinal tract</p> Signup and view all the answers

    Study Notes

    Pathogenicity and Virulence

    • Pathogenicity: the ability of a microbe/pathogen to cause disease in a host
    • Virulence: the enhanced ability of a pathogen to cause infection
    • Virulence factor: a characteristic or trait of the pathogen that makes it harmful, e.g., capsules, toxins, antigenic variation

    Toxins

    • Some bacteria can produce toxins, which can cause death of the host (lethality)
    • LD50 (Lethal Dose 50): the amount of toxin required to kill 50% of the population, measures potency of a toxin
    • Pathogens with low LD50 = high lethality, pathogens with high LD50 = low lethality
    • Types of toxins: exotoxins, endotoxins
    • Toxigenicity: the ability of a pathogen to produce a toxin
    • Toxemia: the presence of toxin in the bloodstream
    • Toxoid: a chemically modified toxin that is no longer toxic
    • Antitoxin: an antibody against a toxin, usually injected into the host (artificial passive immunity)

    Mechanisms of Pathogenicity

    • Adhesion factors: ability of pathogens to attach to host tissues/cells
    • Bacterial adhesins (ligands): substances on the pathogen that bind to receptors on host cells
    • Types of adhesins: capsules, fimbriae, M proteins, Opa proteins, hooks

    Penetration Factors (Bacterial Enzymes)

    • Coagulase: helps form blood clot, stops blood flow, and prevents host defenses from reaching the bacterium
    • Kinase: breaks down blood clot surrounding the bacterium, allowing it to spread throughout the body
    • Hyaluronidase: breaks down hyaluronic acid in connective tissue
    • Collagenase: breaks down collagen in connective tissue
    • IgA protease: destroys IgA antibodies in the mucosa

    Evasion of Host Defenses

    • Survival inside phagocytes: pathogen escapes from phagosome before lysosomal fusion, prevents fusion of lysosome with phagosome, and resists lysosomal enzymes
    • Antigenic variation: pathogen changes its surface antigens (antigenic determinants) through genetic mutations/recombination

    Damage to Host Cells

    • Toxins: poisonous substances (acting as antigens) produced by pathogens, can produce fever, cardiovascular problems, diarrhea, and shock
    • Types of toxins: exotoxins, endotoxins

    ID50 (Infectious Dose 50)

    • The number of pathogens required to make 50% of the population sick
    • Measures virulence of a microbe
    • Infectious pathogens have different ID50's: pathogens with low ID50 = high infectiousness, pathogens with high ID50 = low infectiousness

    Portals of Entry

    • Mucous membranes
    • Skin
    • Parenteral route (non-oral entry): pathogens directly deposited into tissue or bloodstream, usually involves an "injection" into a blood vessel

    Pathogenic Properties of Fungi

    • Some fungal toxins can contaminate the food supply, provoke an allergic response, and are carcinogenic (cancer-causing)

    Pathogenic Properties of Parasitic Protozoa

    • Large number of protozoa feed on host tissue, causing damage to intestinal lining and resulting in diarrhea or dysentery
    • Protozoa avoid host defenses by growing in phagocytes and antigenic variation

    Pathogenic Properties of Parasitic Helminths

    • Helminths = worms, not very pathogenic
    • Use host's nutrients or tissues without killing the host
    • Presence in the GI tract in large numbers interferes with host food absorption, leading to symptoms of fatigue and weight loss

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    Test your knowledge on the microbial mechanisms of pathogenicity, including concepts such as virulence, virulence factors, and portals of entry for microbes into a host. Explore how pathogens cause infectious diseases and the traits that make them harmful.

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