Bacterial Pathogenesis and Infections
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Questions and Answers

Which stage of the infectious disease process involves adherence to host surfaces?

  • Transmission from exogenous sources
  • Multiply and disseminate within the body (correct)
  • Cause cell and tissue damage
  • Overcome host defenses
  • What does the 'iceberg' concept of infectious disease emphasize about asymptomatic infections?

  • They play a role in immunity and potential reinfection. (correct)
  • They always lead to severe illness.
  • They are identifiable in the community.
  • They only occur in immune-compromised individuals.
  • Which of the following is NOT considered a physical or chemical barrier to prevent bacterial infection?

  • Mucous in the respiratory tract
  • Presence of healthy gut flora (correct)
  • Skin fatty acids
  • Acid in the stomach
  • In the iceberg concept, which section represents the asymptomatic infections?

    <p>Hidden – the largest section (A)</p> Signup and view all the answers

    What is the major role of asymptomatically infected individuals in a community?

    <p>To serve as a reservoir for future outbreaks. (C)</p> Signup and view all the answers

    What term describes the ability of a microbial species to produce disease?

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

    Which type of infection is characterized by the first infection by a pathogen in a new host?

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

    What is the minimum number of bacteria required to produce clinical evidence of infection called?

    <p>Minimum Infective Dose (MID) (C)</p> Signup and view all the answers

    Which type of infection occurs due to a new pathogen infecting a host already suffering from an existing disease?

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

    Which term describes localized infections with generalized systemic effects?

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

    What do we call the state when some pathogens remain dormant after primary infection and may cause disease later?

    <p>Latent infection (B)</p> Signup and view all the answers

    Which type of infection is specifically induced by a physician during treatment or procedures?

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

    What is the difference in virulence among strains of the same organism caused by the expression of certain factors called?

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

    What is the presence of bacteria in the blood known as?

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

    Which type of infection arises from the host's own body?

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

    What is the primary role of pili or fimbriae in bacterial function?

    <p>To mediate adhesion to surfaces (C)</p> Signup and view all the answers

    Which organism is specifically associated with the use of Colonization Factor Antigens (CFA)?

    <p>Enterotoxigenic Escherichia coli (ETEC) (D)</p> Signup and view all the answers

    What distinguishes a capsule from a slime layer in bacterial structures?

    <p>Capsules are tightly attached and made of polysaccharide. (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of biofilm formation?

    <p>Ability to enhance respiratory function (D)</p> Signup and view all the answers

    How do bacterial capsules help in immune evasion?

    <p>By protecting against phagocytosis (C)</p> Signup and view all the answers

    What is a key feature of the filamentous haemagglutinin (FHA) produced by Bordetella pertussis?

    <p>Mediates adhesion to ciliated epithelial cells (A)</p> Signup and view all the answers

    Which of the following bacteria is associated with biofilm formation in implanted devices?

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

    What allows pili to confer host specificity in bacteria?

    <p>The properties of their tip (B)</p> Signup and view all the answers

    What is one of the main consequences of exposure to high levels of endotoxin?

    <p>Decreased blood pressure (D)</p> Signup and view all the answers

    Which of the following cytokines is primarily activated by endotoxin?

    <p>TNF-a (C)</p> Signup and view all the answers

    Which bacteria is most commonly associated with endotoxic (septic) shock?

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

    What systemic effect is NOT caused by high doses of endotoxin?

    <p>Diabetes (B)</p> Signup and view all the answers

    How does endotoxin primarily induce its effects?

    <p>Inducing the immune response (C)</p> Signup and view all the answers

    What effect does tetanospasmin have on skeletal muscles?

    <p>It leads to continuous stimulation and contraction. (A)</p> Signup and view all the answers

    What neurotransmitter is primarily affected by botulinum toxin?

    <p>Acetylcholine (B)</p> Signup and view all the answers

    Which of the following describes the action of botulinum toxin?

    <p>It results in flaccid paralysis of skeletal muscles. (A)</p> Signup and view all the answers

    Inhibitory neurotransmitters include which of the following?

    <p>Glycine and GABA (B)</p> Signup and view all the answers

    What type of paralysis is associated with botulism?

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

    Which structure is primarily responsible for the production of botulinum toxin?

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

    What is the main physiological effect of tetanospasmin on the body?

    <p>It causes involuntary contractions. (B)</p> Signup and view all the answers

    What type of toxin is botulinum toxin classified as?

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

    What type of appearance do capsules give to bacterial colonies?

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

    Which stain is used to demonstrate bacterial capsules under a light microscope?

    <p>India ink stain (D)</p> Signup and view all the answers

    Which enzyme is responsible for breaking down the connective tissue component hyaluronic acid?

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

    What type of bacteria are endotoxins characteristic of?

    <p>Gram-negative bacteria (D)</p> Signup and view all the answers

    What do exotoxins typically consist of?

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

    Which enzyme produced by Staphylococcus aureus helps in creating a fibrin barrier?

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

    What is the main function of urease produced by Proteus and H. pylori?

    <p>Producing ammonia from urea (D)</p> Signup and view all the answers

    Which of the following enzymes breaks down red blood cells?

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

    Flashcards

    Bacterial Pathogenesis

    The process by which bacteria cause disease.

    Pathogenicity

    The ability of a microbe to cause disease.

    Virulence

    The degree of pathogenicity (harm caused); may vary between strains.

    Primary Infection

    The initial infection by a pathogen.

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    Reinfection

    A subsequent infection by the same pathogen.

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    Secondary Infection

    New infection by a different pathogen due to weakened resistance.

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    Minimum Infective Dose (MID)

    The minimum amount of bacteria needed to cause infection.

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    Minimum Lethal Dose (MLD)

    The minimum amount of bacteria needed to cause death.

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    Normal Flora

    Microorganisms that live harmlessly in the body.

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    Septicemia

    Bacteria multiplying in the blood, causing fever and toxicity.

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    Epidemiological Triad stages

    Transmission from external sources or infected individuals, entry into the human body, overcoming host defenses, multiplication and spreading within the body, causing cell tissue damage, and spreading to others.

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    "Iceberg" Concept of Infectious Disease

    Many infectious diseases have symptomatic, less severe, and asymptomatic cases. Asymptomatic cases are crucial because they develop immunity and spread infection unknowingly.

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    Host Physical & Chemical Barriers

    The body's natural defenses against bacterial infections, including skin's high salt and fatty acids, stomach acid, mucous and cilia in the respiratory tract, peristalsis in the digestive tract, and soluble mediators.

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    Asymptomatic Infections (Iceberg)

    Infections that do not show any noticeable symptoms in the infected person. They can still spread the infection to others.

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    Classic Clinical Disease (Iceberg)

    The evident, symptomatic stage of an infectious disease, representing the visible tip of the disease iceberg.

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    What is Endotoxin?

    A toxic component of the outer membrane of Gram-negative bacteria. It's a potent stimulator of the immune system and can lead to serious complications like septic shock.

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    What causes Endotoxic (Septic) Shock?

    Exposure to high levels of endotoxin (LPS) from Gram-negative bacteria. This triggers a cascade of immune responses, leading to systemic inflammation, blood clotting abnormalities, and potentially organ failure.

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    What are the effects of Endotoxin on the body?

    Endotoxin activates multiple pathways including cytokine release, clotting, and complement. This can lead to fever, inflammation, blood pressure drop (hypotension), and even death in severe cases.

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    How does Endotoxic Shock relate to Bacteria?

    Endotoxic shock is primarily associated with infections caused by certain Gram-negative bacteria, like Escherichia coli, Pseudomonas aeruginosa, and Neisseria meningitidis.

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    What are the consequences of high doses of Endotoxin?

    High levels of endotoxin can cause systemic effects like fever, hypotension, weakness, disseminated intravascular coagulation (DIC), inflammation, and even intestinal hemorrhage.

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    Pili/Fimbriae

    Short, hair-like structures on bacterial cell surfaces that mediate adhesion to surfaces, aiding infection.

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    Bacterial Adherence

    The ability of bacteria to attach to surfaces, a critical step in infection.

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    Colonization Factor Antigens (CFA)

    Antigenically specific fimbriae/pili used by Enterotoxigenic Escherichia coli (ETEC) to colonize the gut.

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    Non-Fimbrial Adhesins

    Bacterial proteins that mediate attachment to host cells, unlike pili type adhesions

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    Biofilm Formation

    Bacterial aggregates on surfaces, providing increased resistance to host defenses and antibiotics.

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    Capsule/Slime Layer

    Bacterial coatings that protect from phagocytosis and aid in adherence to surfaces.

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    Phagocytosis

    The process by which white blood cells engulf and destroy bacteria.

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    Capsule

    A protective layer surrounding some bacteria, composed of polysaccharides. It contributes to the mucoid appearance of colonies and can be visualized with India ink staining. Capsules are often associated with bacterial virulence.

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    Hyaluronidase

    An enzyme produced by some bacteria that breaks down hyaluronic acid, a component of connective tissue. This allows bacteria to spread through tissues.

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    Hemolysins

    Enzymes that break down red blood cells. Examples include alpha and beta hemolysins produced by Staphylococci and Streptococci. Hemolysis can be observed as zones of clearing around colonies on blood agar.

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    Coagulase

    An enzyme produced by Staphylococcus aureus that converts fibrinogen to fibrin, forming a fibrin barrier around the bacteria. This protects the bacteria from the immune system.

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    Streptokinase

    An enzyme produced by Streptococcus pyogenes that breaks down fibrin. This helps the bacteria spread through tissues.

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    Endotoxin

    A component of the outer membrane of Gram-negative bacteria, released when the bacteria die. Endotoxins are typically lipopolysaccharides and can trigger a strong inflammatory response in the host.

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    Exotoxin

    A toxic protein secreted by some bacteria. Exotoxins can have a variety of effects on the host, including damage to tissues, interference with cellular functions, and immune suppression.

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    What is the role of endotoxin in pathogenesis?

    Endotoxins activate various immune pathways, leading to a cascade of inflammatory and immune responses. These responses can be beneficial in clearing infections, but they can also contribute to tissue damage and organ dysfunction during severe infections.

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    Tetanus Toxin (TeNT)

    A neurotoxin produced by the bacterium Clostridium tetani that blocks the release of inhibitory neurotransmitters, causing continuous muscle contraction and spasms.

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    Botulinum Toxin

    A neurotoxin produced by Clostridium botulinum that blocks the release of acetylcholine, causing muscle paralysis and flaccid weakness.

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    Inhibitory Neurotransmitters

    Chemicals released by nerve cells that reduce or prevent the activity of other nerve cells, leading to muscle relaxation.

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    Excitatory Neurotransmitters

    Chemicals released by nerve cells that stimulate the activity of other nerve cells, leading to muscle contraction.

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    Virulence Factors

    Traits of bacteria that enhance their ability to cause disease, such as toxins, capsules, or enzymes.

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    What is the mechanism of action of tetanus and botulinum toxin?

    Tetanus toxin blocks the release of inhibitory neurotransmitters, leading to continuous muscle contraction. Botulinum toxin blocks the release of acetylcholine, leading to muscle paralysis.

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    Study Notes

    Bacterial Pathogenesis

    • Bacterial pathogenesis is the process of disease production by bacteria.
    • Pathogenicity refers to the ability of a microbial species to produce disease.
    • Virulence is the relative degree of pathogenesis, which can vary between strains of the same organism based on virulence factor expression.
    • Virulence factors influence how bacteria cause disease and how they overcome host defenses.

    Types of Infection

    • Primary infection: Initial infection with a new pathogen.
    • Reinfection: Subsequent infection with the same pathogen.
    • Secondary infection: New infection due to immunodeficiency caused by a primary infection.
    • Focal infection: Localized infection in organs or tissues (e.g., tonsils, appendix, dental abscess). Can spread systemically.
    • Cross-infection: New infection in a patient already suffering from a disease, often seen in hospitals.
    • Latent infection: Some pathogens remain dormant in tissues after primary infection and multiply when host resistance is lowered.
    • Co-infection: Simultaneous infection by multiple pathogens (e.g., HBV and HDV).
    • Bacteremia: Bacteria circulating in the bloodstream.
    • Septicemia: Bacteria circulating and multiplying in the bloodstream, leading to toxic products and a high fever.
    • Iatrogenic infection: Infection induced by a physician's procedure.
    • Exogenous infection: Infection from external sources.
    • Endogenous infection: Infection from the host's own body.
    • Inapparent infection: Infection without clinical symptoms.
    • Atypical infection: Infection with atypical or non-classical clinical features.
    • Nosocomial Infection: Hospital-acquired infection.

    Medical Terms

    • Minimum Infective Dose (MID): Minimum inoculum size or number of bacteria to initiate infection.
    • Minimum Lethal Dose (MLD): Minimum number of bacteria needed to cause host death.
    • Normal Flora: Microorganisms that continuously inhabit the human body (without harm).

    Chain of Infection

    • Infectious Agent: The causative microorganism
    • Reservoir: Location where the microbe thrives
    • Entry: Portal of entry into the host
    • Transmission: Method of spreading the microbe
    • Exit: Portal of exit from the host
    • Susceptible Host: Host susceptible to contracting the disease

    Bacterial Disease Mechanisms

    • Transmission from sources or infected individuals (epidemiological triad).
    • Entry into human body.
    • Overcome host defenses.
    • Multiply and disseminate within the body (adhere to host surfaces, invade cells, cause damage).
    • Spread to other members of the population.

    Virulence Factors

    • Adhesins: (pili/fimbriae/adhesins) mediate attachment to host cells.
    • Capsules/Slime: protect Bacteria, evade immunity and enhance adherence.
    • Toxins: (endotoxins or exotoxins) cause damage by damaging cells or disrupting cellular metabolism.
      • Endotoxins: integral component of the cell wall, released when the cell dies, usually lipopolysaccharides unique to gram-negative bacteria.
      • Exotoxins: heat-labile protein secreted by bacteria.

    Examples of Important Bacterial Virulence Factors

    • Pili/fimbriae: Appendages aiding attachment to host cells (e.g., Neisseria gonorrhoeae, Escherichia coli).
    • Non-fimbrial adhesins: (e.g., Bordetella pertussis - filamentous haemagglutinin (FHA)).
    • Capsules: Polysaccharide/protein coat, evade immunity (e.g., Streptococcus pneumoniae, Klebsiella pneumoniae, Neisseria meningitidis).
    • Toxins: Clostridium perfringens (alpha toxin/Lecithinase, perfringolysin 0), Corynebacterium diphtheriae (diphtheria toxin), Vibrio cholerae (cholera toxin), Clostridium tetani (tetanospasmin), Clostridium botulinum (botulinum toxin)) causing damage from modifying intracellular targets and/or acting on nerve-muscle transmission.

    Host Factors in preventing infection:

    • Physical and chemical barriers (e.g., skin, acid in stomach, mucous).
    • Innate immune responses (e.g., complement, phagocytosis).
    • Adaptive immune responses (e.g., antibodies, cell-mediated immunity).

    Systemic Effects of High Doses of Endotoxin:

    • Fever.
    • Hypotension.
    • Shock.
    • Weakness.
    • Blood coagulation (DIC).
    • Inflammation.
    • Intestinal hemorrhage.

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    Description

    Explore the mechanisms of bacterial pathogenesis and the various types of infections they cause. This quiz covers concepts like pathogenicity, virulence, and different infection types such as primary, secondary, and latent infections. Understand how bacteria interact with hosts and the implications for health.

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