Microbial Mechanisms of Pathogenicity
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Questions and Answers

Which component of bacterial pathogens helps prevent engulfment by phagocytes?

  • Glycocalyx
  • Capsules (correct)
  • Fimbriae
  • Pili

    • Which of the following proteins is known to inhibit phagocytosis in certain bacteria?

  • Siderophore
  • M protein (correct)
  • Opa protein
  • Mycolic acid

    • How do biofilms contribute to antibiotic resistance?

  • By providing a protective environment against antibiotics (correct)
  • By preventing nutrient absorption
  • By making bacteria more virulent
  • Through enhanced bacterial metabolism

    • What is the role of siderophores in bacterial pathogenesis?

    <p>Chelating iron to acquire nutrients (D)</p> Signup and view all the answers

    What is defined as the presence of toxins in the blood?

    <p>Toxemia (C)</p> Signup and view all the answers

    What factor is NOT associated with the formation of biofilms?

    <p>High concentration of antibiotics (B)</p> Signup and view all the answers

    Which mechanism allows pathogens to disrupt host cell functions?

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

    What term describes the ability of a microorganism to produce toxins?

    <p>Toxigenicity (D)</p> Signup and view all the answers

    What type of toxin is produced mainly by gram-positive bacteria?

    <p>Exotoxins (A)</p> Signup and view all the answers

    Which of the following describes A-B toxins?

    <p>They bind to host membranes and have an active component. (D)</p> Signup and view all the answers

    How do endotoxins typically affect the body?

    <p>They can cause fever and shock. (D)</p> Signup and view all the answers

    What is the composition of an exotoxin?

    <p>Protein. (C)</p> Signup and view all the answers

    What is one key difference between exotoxins and endotoxins?

    <p>Exotoxins are generated during bacterial growth, whereas endotoxins are released upon bacterial death. (B)</p> Signup and view all the answers

    Which of the following best describes the role of antitoxins?

    <p>They neutralize exotoxins and provide immunity. (D)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of endotoxins?

    <p>They are soluble in the bloodstream. (D)</p> Signup and view all the answers

    Cytotoxins primarily function to:

    <p>Damage or kill host cells. (C)</p> Signup and view all the answers

    What is the primary role of adherence in microbial pathogenicity?

    <p>To establish pathogens at the appropriate portal of entry. (A)</p> Signup and view all the answers

    What does the term virulence measure in relation to pathogens?

    <p>The likelihood of causing disease in a host. (B)</p> Signup and view all the answers

    Which of the following defined the Infectious Dose (ID50)?

    <p>The number of microbes needed to cause infection in 50% of inoculated hosts. (B)</p> Signup and view all the answers

    How do pathogens typically evade host defenses after adhering to host cells?

    <p>By using capsules and specific components of their cell walls. (C)</p> Signup and view all the answers

    Which of the following is NOT a method by which pathogens can damage host cells?

    <p>Inducing apoptosis in host immune cells. (A)</p> Signup and view all the answers

    What typically occurs at the portals of exit for microbes?

    <p>The same portals of entry are often used. (A)</p> Signup and view all the answers

    What is the significance of adhesion in bacterial infection?

    <p>It secures the pathogen's position to colonize the host. (A)</p> Signup and view all the answers

    Which of the following best describes endotoxins?

    <p>Components of the bacterial cell wall that can elicit a strong immune response. (A)</p> Signup and view all the answers

    What is primarily responsible for causing fever as a pyrogenic response?

    <p>Endotoxins (C)</p> Signup and view all the answers

    Which of the following is a way plasmids contribute to pathogenicity?

    <p>Carrying antibiotic resistance genes (C)</p> Signup and view all the answers

    What is a characteristic of viruses regarding their interaction with host cells?

    <p>They have attachment sites for receptors on host cells. (B)</p> Signup and view all the answers

    What are cytopathic effects (CPE) associated with viral infections?

    <p>Formation of inclusion bodies and cell lysis (A)</p> Signup and view all the answers

    Which organism is categorized under producing A-B toxins and also demonstrates lysogenic conversion?

    <p>Corynebacterium diphtheriae (A)</p> Signup and view all the answers

    Which is NOT a common method through which fungi exert pathogenic effects?

    <p>Releasing neurotoxins (D)</p> Signup and view all the answers

    How do protozoa evade the immune response of the host?

    <p>By changing their surface antigens (B)</p> Signup and view all the answers

    Which of the following organisms is known to produce paralysis-causing neurotoxins when ingested?

    <p>Algae (C)</p> Signup and view all the answers

    What is one of the common portals of exit for pathogens?

    <p>Respiratory tract via coughing or sneezing (B)</p> Signup and view all the answers

    Which portal of exit is associated with gastrointestinal transmission?

    <p>Saliva or feces (D)</p> Signup and view all the answers

    What role do arthropods play in pathogen transmission?

    <p>Provide a portal of exit for microbes in blood (A)</p> Signup and view all the answers

    Which of the following is NOT a portal of exit for pathogens in the human body?

    <p>Nervous system (A)</p> Signup and view all the answers

    Microbes can exit the body through which of the following means?

    <p>Secretions from the vagina or penis (D)</p> Signup and view all the answers

    Study Notes

    Microbial Mechanisms of Pathogenicity

    • Pathogen: A microorganism that can cause disease.
    • Pathogenicity: The ability of a pathogen to cause disease by overcoming the host's defenses.
    • Virulence: The degree of pathogenicity, a measure of a pathogen's ability to cause disease.

    Stages of Microbial Pathogenicity

    • Portals of Entry: Microbes enter the body through various portals: skin, mucous membranes (respiratory, gastrointestinal or genitourinary tract or the conjunctiva), and the parenteral route.
    • Adherence: Microbes attach to host cells by binding their ligands/adhesins to host cell receptors via complementary chemical interactions.
    • Penetration or Evasion of Host Defenses: Microbes evade host defenses, such as phagocytosis, by using capsules, cell wall components, enzymes, antigenic variation, or invading host cells.
    • Damage to Host Cells: Microbes damage host cells by using host nutrients (siderophores), direct damage through their metabolism, or by releasing toxins.
    • Portals of Exit: Microbes generally use the same portals of entry for exit but can also use arthropods or syringes.

    Numbers of Invading Microbes

    • ID50 (Infectious Dose): The number of microbes required to infect 50% of inoculated animals.
    • LD50 (Lethal Dose): The number of microbes required to kill 50% of inoculated animals.

    Adherence

    • Colonization: The establishment of a pathogen at the appropriate portal of entry.
    • Adherence: Microorganisms attach to cells using receptors and ligands.
    • Bacterial Adhesins: Can be found in capsules, cell walls, glycocalyx, pili or fimbriae.
    • Viral Adhesins: Found in viral capsids or envelope components.
    • Host Receptors: Often glycoproteins located on the cell membrane or tissue surface.
    • Specificity: The interaction between ligand and receptor can determine the specific host cells the microbe can infect.
    • Avirulence: Inability to produce attachment proteins or adhesins can render the microorganisms avirulent.

    Biofilms

    • Biofilms: Masses of microbes and their extracellular products that facilitate the attachment of free-floating microorganisms to a surface using cell adhesion structures.
    • Quorum Sensing: Bacteria in biofilms communicate with each other to coordinate activities.
    • Antibiotic Resistance: Biofilms are often associated with antibiotic resistance.

    How Bacterial Pathogens Penetrate Host Defenses

    • Capsules: Prevent engulfment by phagocytes (e.g., Streptococcus pneumoniae, Haemophilus influenzae, Bacillus anthracis).
    • Cell Wall Components: Proteins in the cell wall can facilitate adherence or prevent phagocytosis.
      • M protein: Resist phagocytosis in Streptococcus pyogenes.
      • Opa protein: Inhibits T helper cells in Neisseria gonorrhoeae.
      • Mycolic acid: (waxy lipid) resists digestion in Mycobacterium tuberculosis.

    How Bacterial Pathogens Damage Host Cells

    • Using the Hosts's Nutrients: Siderophores are specialized molecules that bind iron, an essential nutrient for many bacteria.
    • Direct Damage: Pathogens metabolize and multiply inside host cells, damaging host cells without toxins.
    • Toxins: Most bacterial damage is caused by toxins.

    Toxin Production

    • Toxins: Poisonous substances produced by microorganisms.
    • Toxigenicity: The ability to produce toxins.
    • Toxemia: The presence of toxins in the blood.
    • Exotoxins: Proteins produced by bacteria and released into the surrounding medium.
    • Endotoxins: Components of the outer portion of the cell wall (lipid A) of gram-negative bacteria.

    Exotoxins

    • Cytotoxins: Kill or damage host cells.
      • Membrane-disrupting toxins: Create pores in cell membranes or disrupt phospholipid bilayers.
    • Neurotoxins: Interfere with nerve impulses.
    • Enterotoxins: Affect the lining of the gastrointestinal tract.
    • Antitoxins: Provide immunity to toxins.
    • Superantigens: Overstimulate the body's immune response, leading to cytokine release and symptoms like fever, nausea, vomiting, diarrhea, shock, and death.
    • Toxoids: Altered toxins used as vaccines (e.g., diphtheria and tetanus).

    Endotoxins

    • Lipid A: The lipid portion of lipopolysaccharides (LPS) found in the outer membrane of gram-negative bacteria.
    • Release: Endotoxins are released when bacterial cells die due to autolysis, external lysis, phagocytosis, or antibiotics.
    • Effects: Fever, shock, blood clotting, tissue death, and death.
    • Blood-Brain Barrier: Endotoxins can weaken the blood-brain barrier, allowing bacteria to cross it.

    Exotoxin vs. Endotoxin

    Feature Exotoxin Endotoxin
    Source Mostly Gram-positive bacteria Gram-negative bacteria
    Relation to microbe By-products of growing cell Part of outer membrane
    Chemistry Protein Lipid A
    Fever? No Yes
    Neutralized by antitoxin? Yes No
    LD50 Small Relatively large

    Plasmids, Lysogeny, and Pathogenicity

    • Plasmids: Can carry genes for antibiotic resistance, toxin production, capsule formation, and fimbriae.
    • Lysogenic Conversion: Bacteriophages can integrate their DNA into bacterial chromosomes, altering the bacteria's properties.
    • Toxins and Capsules: Lysogeny can lead to the production of toxins and capsules by bacteria.

    Pathogenic Properties of Viruses

    • Attachment: Viruses gain access to cells by binding to receptors on the host cell surface.
    • Immune Evasion: Viruses hide within host cells to avoid the immune system.
    • Cytopathic Effects: Visible effects of viral infections.
      • Cytocidal effects: Cell death.
      • Noncytocidal effects: Damage but not death.
    • Cytopathic Effects: Include:
      • Inhibition of mitosis
      • Lysis (release of lysosomal enzymes)
      • Transformation (abnormal cell growth)
      • Inclusion bodies (viral components accumulating within cells)
      • Cell fusion
      • Antigenic changes
      • Chromosomal changes

    Pathogenic Properties of Fungi, Protozoa, and Algae

    • Fungi: Secrete enzymes, produce toxins, and cause allergic responses.
    • Protozoa: Damage host tissue, release metabolic waste products, and can change surface antigens to avoid the immune system.
    • Algae: Some algae produce neurotoxins.

    Portals of Exit

    • Exit Portals: Microbes leave the body through the respiratory tract (coughing, sneezing), gastrointestinal tract (saliva, feces), genitourinary tract (vaginal or penile secretions), or through arthropods or syringes (in blood).

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    Microbial Mechanisms of Pathogenicity PDF

    Description

    Explore the complex world of microbial pathogenicity in this quiz. Understand key concepts such as pathogen mechanisms, portals of entry, and how microbes evade host defenses. Dive deep into the stages that contribute to disease and enhance your knowledge of microbiology.

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