Lecture 1 Pathogenesis of microbial diseases
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Questions and Answers

Which of the following statements best describes exotoxins?

  • They are released from dead bacteria.
  • They are primarily found in gram-negative bacteria.
  • They are produced and released by living bacteria. (correct)
  • They result in generalized effects on host cells.

    • Endotoxins are typically associated with gram-positive bacteria.

    False

    What are pathogenicity islands?

    Genomic regions of pathogens that encode for virulence factors.

    What is a characteristic of indigenous microbiota?

    <p>They are usually harmless and help to prevent colonization by pathogens.</p> Signup and view all the answers

    Exotoxins can kill host cells and aid in the ________ of bacteria in tissues.

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

    Match the following types of toxins with their characteristics:

    <p>Endotoxin = Released when a bacterial cell is destroyed Exotoxin = Produced and released by living bacteria Botulism toxin = Interferes with neuromuscular functions Diphtheria toxin = Inhibits protein synthesis</p> Signup and view all the answers

    Virulence factors only aid in attachment to host cells.

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

    What is one way microbes compete with the host for nutrients?

    <p>Production of siderophores.</p> Signup and view all the answers

    What effect can endotoxins have on the host's body?

    <p>They can lead to disseminated intravascular coagulation.</p> Signup and view all the answers

    Pathogenicity islands can only be found in one bacterial species.

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

    Microbial strategies to overcome host defenses include achieving __________ to host cell surfaces.

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

    Match the following microbial strategies with their descriptions:

    <p>Pili = Structures that aid in adherence to host cells Capsules = Protective layer against host immune response Biofilms = Community of microorganisms that enhances survival Siderophores = Molecules that capture essential nutrients</p> Signup and view all the answers

    What is a common effect caused by endotoxins?

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

    Which of the following is NOT a host factor that can break barriers?

    <p>Microbial biofilm formation</p> Signup and view all the answers

    All pathogens possess the same virulence factors.

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

    Name one method through which microbes can survive against environmental conditions.

    <p>Localization in moist areas.</p> Signup and view all the answers

    What term describes the ability of a microorganism to cause disease?

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

    Virulence is the term used to describe the degree of pathogenicity of a microorganism.

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

    What happens when an infection produces notable changes in human physiology?

    <p>Disease occurs</p> Signup and view all the answers

    The ______________ of a pathogen can greatly affect the development of infections.

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

    Match the following sources of reservoirs with their types of organisms:

    <p>Humans = Infected individuals Animals = E.g., meat consumption Environment = E.g., water, soil Indigenous flora = Commensal organisms</p> Signup and view all the answers

    Which of the following modes of transmission involves direct contact?

    <p>Direct transmission</p> Signup and view all the answers

    Colonization of host surfaces is always harmful to the human host.

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

    List one way through which indirect transmission of pathogens can occur.

    <p>Through fomites</p> Signup and view all the answers

    Study Notes

    BIOL 2010 Lecture 1 - Pathogenesis of Microbial Disease

    • Course: BIOL 2010
    • Lecture: Pathogenesis of Microbial Disease
    • Textbook: Bailey and Scott's, Chapter 3
    • Topics covered in lecture:
      • Infection versus infectious disease
      • Normal flora and their role in infection
      • Primary and secondary infections
      • Phases of infectious process
      • Characteristics and pathogenesis of common microorganisms (grouped by body system)
      • Bacterial virulence
      • Endotoxins and exotoxins

    Thought Questions

    • What makes some microbes pathogenic and others not?
    • If microbes are everywhere, why don't we get more infections?

    Host-Microbe Relationships

    • Symbiosis: Two organisms living together.
      • Commensalism: Microorganism benefits, host is not harmed.
      • Mutualism: Both microorganism and host benefit.
      • Parasitism: Microorganism benefits, host is harmed.
    • Indigenous (normal) flora: Microorganisms commonly found on or in healthy people.
      • Colonization: Growth of microbiota without causing damage or symptoms.
      • Resident microbiota: Microorganisms colonizing for months or years.
      • Transient flora: Microorganisms temporarily colonizing a host.
      • Carrier state: Condition of a host capable of transmitting the infection.

    Host-Microbe Relationships (continued)

    • Pathogenic: Organism causes disease
      • Ex: Salmonella
    • Nonpathogenic: Organism doesn't cause disease
      • Ex: Corynebacteria (skin flora)
    • Opportunistic pathogen: Organism causes disease only when host defenses are compromised
      • Ex: Indigenous flora

    Terms

    • Pathogenicity: Degree to which a microorganism causes disease.
      • Pathogens: Highly pathogenic, cause significant harm to host.
      • Non-pathogens: Low pathogenicity.
    • Virulence: Degree of pathogenicity.

    Common Microbiota in Humans

    • Includes a variety of microorganisms, grouped by body system (e.g., ears, circulatory, GI tract, skin, LRT, GU).
    • Locations that are normally sterile (e.g., serous fluids, CSF, deeper tissues)

    Host-Microbe Interactions

    • Infection: Growth and multiplication of microorganisms causing damage to the host.
    • Disease: Infection causing notable changes in human physiology.
    • Infectious disease: Transmissible disease.

    Host-Microbe Encounters

    • Reservoirs: The origin of the etiologic agent.
      • Humans (including indigenous flora, infected individuals)
      • Animals
      • Environment (water, soil)
    • Transmission Types:
      • Direct: Host directly encounters the microbial reservoir.
      • Indirect: Host encounters the microbe through an agent.
        • Fomites (non-living): Objects.
        • Vectors (living): Animals and insects.

    Colonization of Host Surfaces

    • Colonization: Microorganisms settle and grow on host surfaces without causing noticeable symptoms.
    • Harmless colonization: Microorganisms can become part of the resident flora or transient colonizers.

    Entry, Invasion, and Dissemination

    • Microorganisms must penetrate or circumvent host physical barriers (skin, mucosal surfaces).
    • Overcoming these defenses depends on host and microbial factors.

    Overview of Host Barriers

    • Physical barriers.
    • Organ-specific defenses.
    • Phagocytes, inflammation, and antibodies.

    Host Barriers - Skin

    • Physical barrier (dry, acidic, cool outer layer).
    • Antimicrobial substances (sebum, sweat).
    • Indigenous flora.
    • Skin-associated lymphoid tissue (SALT).

    Host Barriers - Mucous Membranes

    • Rapid sloughing of mucosal cells and mucus production.
    • Antimicrobial substances (lactoferrin, lysozymes, lactoperoxidase).
    • Mucosa-associated lymphoid tissue (MALT).

    Host Barriers - Other Nonspecific Barriers

    • Oral cavity (saliva, IgA, lysozyme).
    • Stomach (low pH, proteolytic enzymes).
    • Small intestines (bile salts, microbiota).
    • Upper respiratory tract (cilia).
    • Vaginal lining (low pH, microbiota, mucus plug).

    Host Barriers - Phagocytes

    • Phagocytes (white blood cells) ingest and destroy foreign particles (bacteria, other pathogens).
    • Phagocytosis: The process by which this occurs.
    • Major phagocytes include: Neutrophils, Monocytes/Macrophages, and Dendritic cells.

    Host Barriers - Inflammation

    • Inflammation: A complex response to tissue injury or infection.
    • Cellular components, swelling, redness, heat, pain.
    • Complement system: Helps enhance phagocyte activity and directly kills bacteria.
    • Coagulation system: Walls off the site of infection.
    • Chemical messengers (cytokines): Enhance immune response.

    Host Barriers - Antibodies

    • Antibodies (immunoglobulins): Proteins secreted by plasma cells (activated B cells).
    • Respond to foreign substances such as chemicals and toxins.
    • Protect host upon subsequent encounters (memory).
    • Found in blood and secretions.

    Overcoming Host Barriers

    • Colonization (first step of infection).
    • Harmless colonization vs. infectious disease.
    • Microorganisms have defenses to overcome host barriers (ex: virulence factors).

    Virulence Factors

    • Virulence factors: Traits that allow pathogens to cause harm to host.
      • Survival against host defenses.
    • Attachment to host cells.
    • Invasion of tissues.

    Virulence Factors (cont.)

    • Toxins: Biochemically active substances that damage host cells
      • Endotoxins
        • Gram negative bacteria
        • Released upon bacterial death
        • Cause generalized effects leading to a number of issues.
      • Exotoxins
        • Produced by living bacteria
        • Bacterial species specific in their effect
        • Can kill host cells or disrupt intracellular processes.
    • Pathogenicity islands: Parts of pathogens' DNA holding virulence factors.
    • Biofilms: Complex communities with resistant properties.

    Outcomes of Infectious Diseases

    • Dependent on host health and virulence of the pathogen.
      • Infection vs disease.
    • Types of infections (acute, chronic, latent, localized, systemic).
    • Stages of infection (incubation, prodromal, illness, convalescent).

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    Lecture 1 – Pathogenesis of Microbial Disease PDF

    Description

    Test your knowledge on exotoxins, endotoxins, and microbial strategies to overcome host defenses. This quiz covers various aspects of pathogenicity islands and the characteristics of indigenous microbiota. Discover how these factors influence the interaction between microbes and their hosts.

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