Bacterial Pathogenesis and Mechanisms Quiz
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Questions and Answers

What role do adhesins play in bacterial colonization?

  • They destroy host tissues.
  • They produce toxins that harm cells.
  • They act as barriers to prevent invasion.
  • They facilitate binding to specific receptors. (correct)
  • Which of the following substances is categorized as an invasin?

  • Enzyme (correct)
  • Exotoxin
  • Capsule
  • Glycocalyx
  • Which type of toxin initiates destructive biological activities within the host?

  • Antitoxin
  • Exotoxin (correct)
  • Endotoxin
  • Cytotoxin
  • What is the primary function of fimbriae in bacteria?

    <p>Facilitating adherence to surfaces</p> Signup and view all the answers

    Which of the following is NOT a mechanism of damage caused by bacteria to the host?

    <p>Nutritional deficiency</p> Signup and view all the answers

    What term describes the genetic traits that lead to damage in the human host?

    <p>Virulence factors</p> Signup and view all the answers

    Which of the following best defines the role of bacterial by-products in virulence?

    <p>They contribute to invasiveness and toxigenicity.</p> Signup and view all the answers

    To successfully cause disease, a pathogen must first:

    <p>Gain access to the host.</p> Signup and view all the answers

    What is the phase of the infection cycle when microbes actively enter host cells?

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

    What role does the size of the bacterial inoculum play in disease causation?

    <p>It is essential for initiating an infection.</p> Signup and view all the answers

    Which condition is likely to increase a person's susceptibility to bacterial infections?

    <p>Congenital defects</p> Signup and view all the answers

    How do gram-negative bacteria often resist host defenses?

    <p>Through their outer membrane structure.</p> Signup and view all the answers

    What is the main purpose of bacterial colonization in the context of infection?

    <p>To establish a stable population on the host.</p> Signup and view all the answers

    Which of the following statements accurately describes exotoxins?

    <p>They can be made into toxoids.</p> Signup and view all the answers

    What type of damage is primarily associated with endotoxins?

    <p>General systemic damage such as fever and hypotension.</p> Signup and view all the answers

    Which type of toxin is produced by Clostridium tetani and Clostridium botulinum?

    <p>Neurotoxins.</p> Signup and view all the answers

    Which of the following is NOT a feature of endotoxins?

    <p>Specific effects on host cells.</p> Signup and view all the answers

    Which bacterial species is an example of an endotoxin-producing organism?

    <p>Escherichia coli.</p> Signup and view all the answers

    What is the major consequence of superantigen activity?

    <p>Rapid immune response and potential shock.</p> Signup and view all the answers

    Which of the following accurately represents a characteristic of superantigens?

    <p>They can induce a response 2000 times stronger than normal.</p> Signup and view all the answers

    What is a defined property of exotoxins compared to endotoxins?

    <p>They have many types based on structure and function.</p> Signup and view all the answers

    What is the primary role of the bacterial capsule in host defense evasion?

    <p>It provides a protective coat that hinders digestion by immune cells.</p> Signup and view all the answers

    How does the M protein of Streptococcus pyogenes aid in evading the immune response?

    <p>By mimicking host connective tissue, causing accidental damage to host cells.</p> Signup and view all the answers

    Which mechanism is NOT a method by which bacteria can escape host defenses?

    <p>Induction of apoplectic cell death in bacteria.</p> Signup and view all the answers

    Which statement best describes the relationship between bacterial virulence and host immune responses?

    <p>Some virulence mechanisms can inadvertently harm the host.</p> Signup and view all the answers

    Which of the following is a consequence of bacterial metabolites like gas and acid production?

    <p>They can cause harm to surrounding host tissues.</p> Signup and view all the answers

    What is the primary focus of invasiveness in bacterial pathogenesis?

    <p>Colonization and multiplication of bacteria</p> Signup and view all the answers

    What distinguishes endogenous toxins from exogenous toxins?

    <p>Exogenous toxins are produced outside the host.</p> Signup and view all the answers

    What role do degradative enzymes play in bacterial pathogenicity?

    <p>They assist in the evasion of immune response.</p> Signup and view all the answers

    Which of the following best describes bacterial virulence?

    <p>The degree to which bacteria can cause disease.</p> Signup and view all the answers

    How do super-antigens contribute to bacterial pathogenesis?

    <p>By inducing a nonspecific activation of T-cells.</p> Signup and view all the answers

    Which process is critical for the initial steps of bacterial pathogenesis?

    <p>Adherence and colonization</p> Signup and view all the answers

    What is the consequence of bacterial by-products during pathogenic processes?

    <p>Resulting in tissue damage and disease symptoms.</p> Signup and view all the answers

    What are the two broad qualities of pathogenic bacteria that contribute to disease?

    <p>Toxigenesis and invasiveness</p> Signup and view all the answers

    Study Notes

    Bacterial Pathogenesis

    • Bacterial pathogenesis is the process by which bacteria cause disease
    • The degree to which the disease is caused is called virulence or pathogenicity
    • Genetic traits that cause damage are called virulence factors
    • Bacteria cause disease by products such as gases and acids, directly damaging tissues, or releasing toxins transported in the blood to cause harm in other organs
    • Virulence involves invasiveness and toxigenicity

    Mechanisms of Bacterial Pathogenicity

    • Invasiveness: The ability of a bacteria to invade tissues.

      • Includes colonization (adherence and initial multiplication)
      • Production of extracellular substances to facilitate invasion (invasins)
      • Ability to bypass or overcome host defense mechanisms
    • Toxigenesis: The ability to produce toxins.

    Introduction

    • Bacteria can invade, adhere, and colonize new environments
    • Bacteria seek food sources (using degradative enzymes)
    • Bacteria try to evade the host's immune system to create a niche to establish a colony
    • Byproducts of bacterial growth (acids, gases) can damage the host

    Intended Learning Outcomes

    • Students should understand the steps involved in bacterial virulence
    • Students should understand the role of colonization, adherence, and invasion in bacterial pathogenesis
    • Students should be able to differentiate between endo and exo toxins
    • Students should know the principles of immunopathogenesis
    • Students should know how superantigens work

    Colonization, Adherence, and Invasion

    • Colonization is the establishment of a pathogen at a portal of entry
    • Ability to colonize depends on the species and environmental conditions
    • Examples: Legionella bacteria do not spread efficiently at higher temperatures

    Adherence

    • Adherence is aided by adhesins that bind to host receptors
    • Microbial structures like glycocalyx and fimbriae (attachment pili) aid adherence
    • Adherence prevents bacteria from being washed away

    Microbial Adhesions

    • Glycoproteins or lipoproteins on glycocalyx, capsule, capsid, pili, fimbriae or flagella assist in bacterial adherence

    Invasion

    • Invasion involves the production of extracellular substances (invasins)
    • These substances either destroy the host's barriers or penetrate host cells
    • Damage due to invasion contributes to disease pathology

    Pathogenic Actions of Bacteria

    • Bacteria cause damage through three mechanisms:
      • Direct damage (tissue destruction)
      • Toxin-induced damage
      • Hypersensitivity reactions

    Toxin-induced Damage

    • Toxins are bacterial products that directly or indirectly harm tissues or initiate harmful biological activities
    • Toxins are often enzymes
    • Toxins can cause cell lysis
    • Toxins are categorized as endotoxins or exotoxins

    Toxins

    • Exotoxins and Endotoxins:

      • Exotoxins: Produced by both Gram-positive and Gram-negative bacteria, released from the cell, protein-based, heat-liable, have specific receptors on host cells and specific effects on the host, toxoids can be produced

      • Endotoxins: Produced only by Gram-negative bacteria, part of the cell wall (lipopolysaccharides), single type, heat-stable, affect diverse host cells and systems, toxoids cannot be made

    • Endotoxins are released when bacteria are killed by phagocytosis or antibiotics

    • Endotoxins cause general damage to the host, leading to fever, hypotension, and weakness

    • Exotoxin Types: There are five types of exotoxins, each with a target:

      • Enterotoxins: Affect the intestines
      • Neurotoxins: Affect nerves
      • Cytotoxins: Kill specific cells
      • Hematologic Toxins: Affect blood cells
      • Superantigens: Cause excessive immune responses, leading to shock

    Endotoxin-Mediated Toxicity

    • Symptoms of Endotoxin toxicity:
      • Fever
      • Leukopenia (low white blood cells) followed by leukocytosis (high white blood cells)
      • Activation of complement
      • Thrombocytopenia (low platelets)
      • Disseminated intravascular coagulation (DIC)
      • Decreased peripheral circulation
      • Shock
      • Death

    Bacterial Virulence Mechanisms

    • Adherence (Colonization): bacteria adhering to host cells
    • Invasion : bacteria penetrating host cells
    • Degradative enzymes: enzymes that break down host tissues
    • Exotoxins: poisonous proteins that damage cells
    • Endotoxin: toxic component part of cell walls
    • Evasion of phagocytic & immune clearance: bacteria dodging immune system
    • By-products of growth (gas, acid): potentially harmful gases and acids by-products produced during bacterial growth
    • Super antigens: proteins that cause a large and damaging immune response

    Bacterial Port of Entry

    • Ingestion, inhalation, trauma, needlestick, arthropod bite, and sexual transmission are possible routes of bacterial entry

    Natural Openings in the Skin

    • Mucous and epithelial cells lining the respiratory tract, lysozyme, tears, mucous, and the acid and bile in the GI tract offer protective defenses.

    Bacteria Factor: Bacterial Inoculum Size

    • The bacterial strain and inoculum size are important in causing disease.
      • Shigellosis requires fewer than 200 bacteria
      • Cholera and Campylobacter require 10⁸ bacteria

    Bacteria Factor: Bacterial Species

    • Many bacteria can avoid host defenses, for example, the outer membrane of Gram-negative bacteria resists lysozyme, bile, and acid
    • Enterobacteriaceae can colonize the GI tract without immediately causing harm

    Host Factors

    • Host factors, such as congenital defects and immunodeficiency, influence bacterial pathogenesis and susceptibility to infection

    Immunopathogenesis

    • The host's immune response is a key factor in the symptoms of bacterial infection
    • The innate, immune, and inflammatory responses triggered by the infection cause the symptoms seen in the host

    Mechanisms for Escaping Host Defenses

    • Bacteria use various mechanisms like encapsulation, mimicking the host to hide, changing their antigens, producing enzymes, destroying phagocytes, etc

    Summary

    • Bacterial pathogenesis is the study of how bacteria cause disease
    • Key components are bacterial virulence factors, mechanisms of pathogenicity (invasion and toxigenesis), toxins (endo and exotoxins), and host responses (immunopathogenesis) and bacterial entry routes

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