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Microbiology: Pathogenicity and Virulence

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Termini in questo insieme (24)

  • What is pathogenicity?

    Pathogenicity is the ability of a microorganism to cause disease.

  • Define virulence.

    Virulence refers to the degree or severity of pathogenicity.

  • What are common portals of entry for pathogens?

    Common portals include mucous membranes (respiratory, digestive, urinary, reproductive tracts), skin, and the parenteral route (direct tissue entry).

  • Which portal of entry is most common for pathogens?

    The respiratory tract is the most common portal of entry for pathogens.

  • What is the infectious dose ID50?

    ID50 is the infectious dose required to infect 50% of a test population, measuring microbial infectivity.

  • What does LD50 represent?

    LD50 is the lethal dose of a toxin or pathogen that kills 50% of a test population.

  • What is adherence in microbial infection?

    Adherence is the attachment of pathogens to host cells, often mediated by adhesins binding to host receptors.

  • Name bacterial and viral structures that aid adherence.

    Fimbriae help bacteria attach; viral spikes help viruses attach to host cells.

  • How do capsules contribute to virulence?

    Capsules impair phagocytosis, helping bacteria evade immune cells.

  • What role does mycolic acid play in pathogenicity?

    Mycolic acid resists digestion by lysosomal enzymes, aiding bacterial survival inside host cells.

  • List enzymes that act as virulence factors.

    Coagulases form clots, kinases digest clots, hyaluronidase digests hyaluronic acid, collagenase breaks down collagen, and IgA proteases destroy IgA antibodies.

  • What is antigenic variation?

    Antigenic variation is the alteration of surface proteins to evade the host immune response.

  • Give examples of pathogens that use antigenic variation.

    Influenza viruses and Neisseria gonorrhoeae use antigenic variation to avoid immunity.

  • How do invasins help pathogens penetrate the host?

    Invasins rearrange host actin filaments causing membrane ruffling, which facilitates bacterial engulfment.

  • What is the significance of biofilms in infections?

    Biofilms protect bacteria from antibiotics and disinfectants and are involved in about 65% of infections.

  • Define exotoxins.

    Exotoxins are proteins secreted by bacteria that target specific host cells and cause damage.

  • What are antitoxins and toxoids?

    Antitoxins are antibodies against toxins; toxoids are inactivated exotoxins used in vaccines.

  • Describe A-B exotoxins.

    A-B toxins have two parts: part A is the enzyme component, and part B binds to the host cell. Example: diphtheria toxin.

  • What are endotoxins?

    Endotoxins are lipid A components of gram-negative bacterial LPS released upon cell death, causing immune activation.

  • Contrast exotoxins and endotoxins.

    Exotoxins are usually proteins, heat labile, and secreted; endotoxins are lipid components, heat stable, and part of the bacterial outer membrane.

  • What is lysogenic conversion?

    Lysogenic conversion occurs when a bacteriophage integrates into bacterial DNA, altering bacterial virulence.

  • How do viruses evade the immune system?

    Viruses evade immunity by living inside host cells and using antigenic variation to avoid detection.

  • What are cytopathic effects?

    Cytopathic effects are visible structural changes in host cells caused by viral infection.

  • Name common portals of exit for pathogens.

    Respiratory pathogens exit via coughing/sneezing, GI pathogens via feces, and bloodborne pathogens via needles or bites.