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Microbial Mechanisms of Pathogenicity - Microbiology

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  • What is pathogenesis?

    Pathogenesis is the process of disease development (infection) in a host.

  • What is the first step in bacterial pathogenesis?

    Exposure to the pathogen through a portal of entry is the first step in bacterial pathogenesis.

  • What are common portals of entry for pathogens?

    Portals of entry include skin, mucous membranes, and parenteral routes (sites bypassing protective barriers). The respiratory tract is the most common portal.

  • Why is wearing a face mask important during respiratory infections like COVID-19?

    Masks cover the openings to the respiratory system, which are the portal of entry and exit for respiratory viruses like SARS-CoV-2.

  • What is adhesion in bacterial pathogenesis?

    Adhesion is the ability of a pathogen to attach to host cells using adhesion factors called adhesins, which bind specific receptors on host cells.

  • Where are adhesins commonly found on bacteria?

    Adhesins are found on bacterial pili, fimbriae, and flagella.

  • What is invasion in bacterial pathogenesis?

    Invasion is when a pathogen enters host cells or tissues, often by inducing endocytosis or membrane ruffling to enter cells and evade the immune system.

  • What is membrane ruffling?

    Membrane ruffling is the rearrangement of actin filaments in the host cell membrane, creating ruffles that engulf bacteria during invasion.

  • What are the three types of infections caused by pathogens?

    Pathogens cause local (confined), focal (spread to a specific location), and systemic (widely spread) infections.

  • What are exotoxins?

    Exotoxins are soluble proteins secreted by pathogens that damage host cells and tissues.

  • What is an endotoxin?

    Endotoxin is the lipopolysaccharide (LPS) component of the outer membrane of gram-negative bacteria, especially the toxic Lipid A portion.

  • What are the three categories of exotoxins?

    Exotoxins include A-B toxins, membrane-damaging toxins, and superantigens.

  • What are A-B toxins?

    A-B toxins have two parts: the A (active) subunit causes damage, and the B (binding) subunit binds specific host cells.

  • What are membrane-damaging toxins?

    Membrane-damaging toxins disrupt host cell membranes causing lysis, including pore-forming toxins and phospholipases.

  • What are superantigens?

    Superantigens are exotoxins that overstimulate T helper cells, causing massive cytokine release called a cytokine storm, which can be life-threatening.

  • What is septic shock caused by endotoxin?

    Septic shock is a systemic inflammatory response caused by Lipid A from endotoxin entering the bloodstream, leading to fever, inflammation, and organ failure.

  • How do endotoxins and exotoxins differ in toxicity?

    Exotoxins are highly toxic and lethal in small doses, while endotoxins are less toxic and require large amounts to cause disease.

  • How can the immune response damage the host?

    Excessive immune responses like inflammation, cytokine storms, and antibody-antigen complexes can cause unintended damage to host tissues.

  • What are some mechanisms pathogens use to avoid phagocytosis?

    Pathogens avoid phagocytosis by producing capsules, degrading complement proteins like C5a, producing toxins that kill phagocytes, and using Fc receptors to block antibody function.

  • What is antigenic variation?

    Antigenic variation is when pathogens alter their surface antigens to evade recognition by host antibodies during adaptive immunity.

  • How do viruses evade the immune response?

    Viruses evade immunity by preventing antiviral protein effects, interfering with MHC I antigen presentation, and changing surface proteins to avoid antibodies.