Pathogenesis of Bacterial Infection
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Questions and Answers

What is a pathogen?

  • A microorganism that is able to cause disease (correct)
  • An organism that always lives in the body without causing harm
  • A microorganism that is helpful to the host
  • A type of bacteria that is beneficial to human health

    • Which of the following refers to the ability of a microorganism to produce disease?

  • Infectivity
  • Pathogenicity (correct)
  • Virulence
  • Immunogenicity

    • What is the percentage of bacteria that can cause disease in humans?

  • 20%
  • 5%
  • 10%
  • < 1% (correct)

    • What differentiates virulent pathogens from opportunistic pathogens?

    <p>Opportunistic pathogens only cause disease under certain conditions</p> Signup and view all the answers

    Which statement best describes virulence?

    <p>The capacity or severity of a microorganism to cause disease</p> Signup and view all the answers

    What are normal flora also known as?

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

    What causes opportunistic bacteria to lead to infections?

    <p>Presence of foreign bodies</p> Signup and view all the answers

    What are virulence factors?

    <p>Pathogenic structural features</p> Signup and view all the answers

    Which of the following is a characteristic of primary pathogens?

    <p>Must escape normal flora to cause infection</p> Signup and view all the answers

    What happens when normal flora escapes from their usual location?

    <p>They can cause infections.</p> Signup and view all the answers

    How do opportunistic bacteria differ from primary pathogens?

    <p>They usually require a compromised host to cause disease.</p> Signup and view all the answers

    What type of bacteria are methicillin-resistant Staphylococcus aureus (MRSA)?

    <p>Opportunistic pathogens</p> Signup and view all the answers

    What is a major factor that influences whether infection occurs?

    <p>The state of the host</p> Signup and view all the answers

    What is the primary function of the enzyme produced by Staphylococcus aureus related to clotting?

    <p>To convert fibrinogen to fibrin</p> Signup and view all the answers

    Which type of toxin is integral to the bacterial cell envelope and causes septic shock?

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

    How do exotoxins primarily function in the body?

    <p>They are secreted by living bacteria.</p> Signup and view all the answers

    What characterizes a superantigen?

    <p>It causes nonspecific activation of T cells.</p> Signup and view all the answers

    Which of the following statements accurately differentiates endotoxins and exotoxins?

    <p>Exotoxins can act locally or distally after being released.</p> Signup and view all the answers

    Which method of pathogen entry involves the consumption of contaminated food?

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

    What is the role of adhesins in the process of infection?

    <p>Aid in adhesion to host cells</p> Signup and view all the answers

    Which of the following is a common mechanism by which bacterial enzymes cause damage to host cells?

    <p>They directly damage host tissue.</p> Signup and view all the answers

    Which of the following is NOT a method by which pathogens evade the immune system?

    <p>Antibody production</p> Signup and view all the answers

    Which type of toxin is most likely to be involved in causing cholera?

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

    What component is primarily released from Gram-negative bacteria upon cell lysis?

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

    Which pathogen uses the mechanism of vertical transmission?

    <p>Group B Streptococcus</p> Signup and view all the answers

    What is the function of invasins produced by pathogens?

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

    How do some bacteria prevent phagosome/lysosome fusion?

    <p>By producing specialized proteins</p> Signup and view all the answers

    What is a key characteristic of the capsule that some bacteria possess?

    <p>It hides the bacteria from antibodies</p> Signup and view all the answers

    What type of enzyme do leucocidins represent?

    <p>Pore forming enzyme targeting immune cells</p> Signup and view all the answers

    Which pathogen commonly causes food poisoning through ingestion?

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

    What process is primarily involved in the adhesion of bacteria to host cells?

    <p>Receptor/ligand mediated processes</p> Signup and view all the answers

    Which method of dissemination refers to the spread through blood?

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

    What is a common transmission route for pathogens via coughing or sneezing?

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

    Which of the following host factors increases susceptibility to infections?

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

    What type of bacterial chemical can cause host cell toxicity by directly damaging host cells?

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

    Which condition is NOT considered a host factor making a person more susceptible to infection?

    <p>Frequent exercise</p> Signup and view all the answers

    Which of the following actions does NOT help pathogens in evading the immune system?

    <p>Enhancing immune system activity</p> Signup and view all the answers

    Which pathway of pathogen spread involves migration through lymphatic vessels?

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

    What term describes the process through which pathogens attach to host cells?

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

    What distinguishes pathogenicity from virulence?

    <p>Pathogenicity is the ability to produce disease, while virulence refers to the capacity to cause severe disease.</p> Signup and view all the answers

    Which statement describes the normal flora in relation to pathogens?

    <p>Normal flora can become pathogenic under certain conditions.</p> Signup and view all the answers

    How do pathogens typically evade the immune system?

    <p>By altering surface proteins to avoid detection.</p> Signup and view all the answers

    What mechanism is primarily employed by bacterial pathogens to enter the body?

    <p>Via mucosal surfaces, such as the gastrointestinal tract.</p> Signup and view all the answers

    What is a key factor that influences a pathogen's ability to spread within the host?

    <p>The presence of host immune responses.</p> Signup and view all the answers

    What condition is likely to lead to normal flora causing an infection?

    <p>Escape from their usual location</p> Signup and view all the answers

    Which type of bacteria typically has a low intrinsic virulence but can cause serious infections under certain conditions?

    <p>Opportunistic bacteria</p> Signup and view all the answers

    What defines virulence factors in pathogens?

    <p>Genetic, biochemical, and structural features enabling disease production</p> Signup and view all the answers

    What best characterizes primary pathogens?

    <p>Able to cause disease due to their presence within the host</p> Signup and view all the answers

    What can trigger opportunistic bacteria to cause infections?

    <p>Presence of a foreign body in an immunocompromised host</p> Signup and view all the answers

    What allows virulent bacteria to exist among normal flora without causing disease?

    <p>Colonization without infection</p> Signup and view all the answers

    What factor does NOT influence whether an infection occurs?

    <p>The prior hygiene of the host</p> Signup and view all the answers

    What contributes to the ability of methicillin-resistant Staphylococcus aureus (MRSA) to cause infections?

    <p>Resistance to standard antibiotics</p> Signup and view all the answers

    What is one method through which pathogens can spread within the body?

    <p>Haematogenous dissemination</p> Signup and view all the answers

    Which of the following host factors can increase susceptibility to infection?

    <p>Old age</p> Signup and view all the answers

    Which transmission method involves the shedding of infectious agents through respiratory droplets?

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

    What is a primary function of adhesion in the context of pathogen infection?

    <p>To establish a stable population of bacteria</p> Signup and view all the answers

    How do pathogens utilize inhibitors to evade the immune response?

    <p>By producing enzymes that target immune cells</p> Signup and view all the answers

    What type of spread involves pathogens moving through lymphatic vessels?

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

    Which of the following processes greatly aids in the invasion of pathogens into host cells?

    <p>Receptor/ligand mediated adhesion</p> Signup and view all the answers

    Which statement describes a factor that can lead to major breaches in skin/mucosa, thus increasing the risk of infection?

    <p>Recent surgery</p> Signup and view all the answers

    What is the role of invasins produced by pathogens?

    <p>They facilitate spread and damage to host cells</p> Signup and view all the answers

    Which of the following best describes the role of macrophages in the context of pathogen spread?

    <p>They can carry pathogens within their cells.</p> Signup and view all the answers

    Which type of entry method involves pathogens passing through mucosal barriers?

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

    What is a common method by which pathogens can evade the immune system?

    <p>Inhibiting phagocytosis</p> Signup and view all the answers

    Which of these conditions does NOT typically make a person more susceptible to infections?

    <p>Adequate sleep</p> Signup and view all the answers

    How do pathogens such as Mycobacterium tuberculosis survive within phagocytes?

    <p>By preventing phagosome/lysosome fusion</p> Signup and view all the answers

    What method do some bacteria use to avoid being cleared by the immune system?

    <p>Forming protective capsules</p> Signup and view all the answers

    Which of the following statements accurately describes immune evasion by bacteria?

    <p>Bacteria can form protective layers to resist phagocytosis</p> Signup and view all the answers

    What specific role do leucocidins play in bacterial survival?

    <p>Damaging immune cells to evade immune responses</p> Signup and view all the answers

    What is the primary role of endotoxins in bacterial infections?

    <p>They induce a pro-inflammatory response.</p> Signup and view all the answers

    Which type of toxin is released primarily during bacterial cell lysis?

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

    What distinguishes exotoxins from endotoxins in terms of their origin?

    <p>Exotoxins are produced by living bacteria, mostly Gram-positive.</p> Signup and view all the answers

    How do superantigens affect the immune system?

    <p>They cause hyperactivation of T cells.</p> Signup and view all the answers

    Which component is specifically associated with endotoxins?

    <p>Lipopolysaccharide (LPS)</p> Signup and view all the answers

    What type of exotoxin mainly targets the gastrointestinal system?

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

    What is a key feature that differentiates the mechanisms of action for exotoxins from endotoxins?

    <p>Exotoxins are secreted actively while endotoxins are passively released.</p> Signup and view all the answers

    Which type of bacterial enzyme is primarily responsible for damaging host cells?

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

    Which statement best describes the relationship between pathogenicity and virulence?

    <p>Pathogenicity is the capacity to cause an infection, while virulence measures the extent of damage caused by the infection.</p> Signup and view all the answers

    What is the primary reason for the difference in disease-causing ability between normal flora and opportunistic pathogens?

    <p>Normal flora is primarily composed of bacteria that are only harmful under unique conditions.</p> Signup and view all the answers

    How do various toxins differ in their effects and source within bacterial pathogens?

    <p>Endotoxins trigger immune responses, while exotoxins primarily disrupt cellular processes directly.</p> Signup and view all the answers

    Which factors contribute most significantly to a pathogen's ability to spread within the host?

    <p>The presence of host immune response and the pathogen's resistance to it.</p> Signup and view all the answers

    What are the primary mechanisms by which pathogens can prevent fusion of phagosomes and lysosomes after entry into a host cell?

    <p>By secreting enzymes that degrade the lysosomal membranes.</p> Signup and view all the answers

    Which of the following mechanisms does NOT contribute to the dissemination of pathogens within the body?

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

    What is the significance of adhesins in the process of infection?

    <p>They enable pathogens to attach to host cells.</p> Signup and view all the answers

    Which of the following factors does NOT increase a host's susceptibility to infections?

    <p>Recent vaccination</p> Signup and view all the answers

    Which of the following best describes a primary pathogen?

    <p>A pathogen capable of causing disease regardless of host immune status.</p> Signup and view all the answers

    What is the primary characteristic that differentiates endotoxins from exotoxins?

    <p>Endotoxins are integral components of the bacterial cell envelope.</p> Signup and view all the answers

    Which type of bacterial toxin is known for causing hyperactivation of the immune system?

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

    What role do endotoxins play in bacterial infections?

    <p>They lead to immune dysregulation and systemic inflammation.</p> Signup and view all the answers

    Which of the following host factors is associated with an increased risk of severe infection manifestation?

    <p>Individuals with chronic respiratory conditions</p> Signup and view all the answers

    Which of the following statements is true about exotoxins?

    <p>They may be released during antibiotic treatment.</p> Signup and view all the answers

    In the context of pathogen transmission, which route is associated with vertical transmission?

    <p>Infections passed from mother to fetus</p> Signup and view all the answers

    When considering the mechanisms of damage inflicted by bacterial enzymes, which of the following is NOT a common outcome?

    <p>Inhibition of bacterial cell division.</p> Signup and view all the answers

    Which condition is least likely to cause opportunistic infections due to compromised host defenses?

    <p>Normal physiological stress levels</p> Signup and view all the answers

    What is a characteristic of endotoxins regarding their release from bacteria?

    <p>They are produced by lysis of the bacterial cell.</p> Signup and view all the answers

    Which class of bacteria primarily produces exotoxins?

    <p>Primarily Gram-positive bacteria</p> Signup and view all the answers

    What is a common effect of endotoxins on the host?

    <p>They induce systemic inflammation leading to septic shock.</p> Signup and view all the answers

    How do superantigens interact with immune cells?

    <p>By non-specifically activating large numbers of T cells.</p> Signup and view all the answers

    What distinguishes opportunistic bacteria from primary pathogens?

    <p>Opportunistic bacteria typically cause infections in immunocompromised persons.</p> Signup and view all the answers

    Which of the following best describes the conditions under which normal flora can cause infection?

    <p>Normal flora can cause infections if they escape from their usual location or if barriers are breached.</p> Signup and view all the answers

    Which term best describes the process by which pathogens attach to host cells?

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

    What is a primary mechanism used by pathogens to evade the immune system?

    <p>Immune cell destruction</p> Signup and view all the answers

    What role do virulence factors play in pathogenic bacteria?

    <p>They enable pathogens to invade or damage the host.</p> Signup and view all the answers

    Which factor is least likely to influence the occurrence of infection in a host?

    <p>The presence of normal flora in other body regions.</p> Signup and view all the answers

    Which class of pathogenic organisms is specifically associated with survival within phagocytes?

    <p>Listeria monocytogenes</p> Signup and view all the answers

    What type of bacterial protein ligands play a crucial role in pathogen adhesion to host cells?

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

    What defines a primary pathogen?

    <p>It is capable of causing disease solely based on its presence within the host.</p> Signup and view all the answers

    Which characteristic is commonly associated with virulent bacteria?

    <p>They possess specialized features that facilitate damage to the host.</p> Signup and view all the answers

    Which of the following is a common biochemical virulence factor that aids pathogen invasion?

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

    What is the mechanism through which some bacteria can prevent phagosome and lysosome fusion?

    <p>Enzyme secretion</p> Signup and view all the answers

    Under what circumstance do opportunistic bacteria typically not cause infections?

    <p>When the individual has a functioning immune system.</p> Signup and view all the answers

    Which pathogen is specifically well-known for causing diseases through vertical transmission?

    <p>Group B Streptococcus</p> Signup and view all the answers

    What best characterizes virulence factors in pathogens?

    <p>They promote the organism's ability to evade host defenses.</p> Signup and view all the answers

    Which mechanism employed by bacteria assists in avoiding clearance from mechanical host defenses?

    <p>Capsule production</p> Signup and view all the answers

    What role do leucocidins play in bacterial immune evasion?

    <p>Killing immune cells</p> Signup and view all the answers

    Which of the following pathogens is primarily known for causing food poisoning due to ingestion?

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

    Study Notes

    Pathogenesis of Bacterial Infection

    • Pathogenesis refers to how microorganisms cause disease.
    • Pathogens are microorganisms capable of causing disease.
    • Pathogenicity is the ability to cause disease, while virulence refers to the severity or capacity of a microorganism to cause disease.

    Normal Flora vs. Virulent & Opportunistic Pathogens

    • Less than 1% of bacteria can cause disease in humans.
    • The majority of bacteria in the human body are part of the normal flora or microbiome, which are typically non-pathogenic.
    • Normal flora can cause infection if they escape their usual location, a barrier is breached, or the host is immunosuppressed.
    • Virulent bacteria have an increased ability to invade or damage the host.
    • Primary pathogens can cause disease as a result of their presence in the host, even if they are among normal flora without causing disease.
    • Virulence factors are genetic, biochemical, or structural features of a pathogen that enhance its ability to produce disease.
    • Opportunistic bacteria have low intrinsic virulence and typically don't cause infections in healthy patients.
    • Opportunistic infections can occur in immunocompromised individuals or when a foreign body is present.

    Transmission and Infection

    • Bacteria must first enter the body through a portal of entry, including ingestion, inhalation, penetration, sexual transmission, or vertical transmission.
    • Adhesins are bacterial protein ligands enabling adherence to host cells, preventing clearance from the host.
    • Invasins are bacterial proteins that damage host cells and facilitate spread and invasion.

    Immune Evasion

    • Bacteria have developed mechanisms to avoid immune clearance, including:
      • Inhibition of phagocytosis: Capsular polysaccharides can prevent phagocytosis.
      • Survival within phagocytes: Bacteria can escape the phagosome, prevent phagosome-lysosome fusion, or survive within the phagolysosome.
      • Immune cell destruction: Some bacteria produce enzymes like leucocidins, streptolysin, and coagulase to target immune cells or prevent their function.

    Damage to Host Cells

    • Bacterial enzymes, including invasins, toxins, and superantigens, damage host cells.

    Toxins: Exotoxins vs. Endotoxins

    • Exotoxins are proteins produced by living bacteria, primarily Gram-positive bacteria, and secreted or released during cell lysis. They can act locally or distally.
    • Endotoxins are integral parts of the bacterial cell envelope, primarily from Gram-negative bacteria, released during cell lysis or turnover.
    • Superantigens are a type of exotoxin that hyperactivate the immune system, causing a shock syndrome.
    • Exotoxins are generally more potent than endotoxins.

    Dissemination of Pathogens

    • Pathogens can spread in the body through:
      • Tissue or tissue plane spread
      • Haematogenous spread (through the bloodstream)
      • Lymphatic spread (through the lymphatic system)
      • Carriage within macrophages
      • Ascending or descending spread within a tract

    Transmission of Pathogens

    • Transmission of pathogens can occur through:
      • Person-to-person direct contact
      • Respiratory transmission (coughing, sneezing)
      • Gastrointestinal transmission (diarrhea)
      • Sexual transmission (genital discharge or ulcers)
      • Vertical or perinatal transmission (from mother to child during pregnancy, delivery, or shortly after birth)

    Host Risk Factors

    • Host factors that increase susceptibility to infection and potentially worsen infection severity include:
      • Extremes of age
      • Diabetes
      • Immunosuppression (disease-induced or medication-induced)
      • Major breach in skin or mucosa (e.g., recent major surgery)
      • Prosthetic material (e.g., IV lines, catheters, ventilators)
      • Anatomical abnormalities or malfunctions
      • Antibiotic therapy (e.g., Clostridium difficile infection)

    Pathogenesis of Bacterial Infection

    • Pathogenesis is the mechanism by which a microorganism causes disease.
    • Pathogen: A microorganism capable of causing disease.
    • Pathogenicity: The ability of an organism to cause disease.
    • Virulence: The degree or severity of a pathogen's ability to cause disease.

    Differentiate Normal Flora From Pathogens

    • Normal flora (microbiome): Microorganisms residing in or on the body without causing disease, commonly non-pathogenic.
    • Virulent bacteria: Organisms which have an increased ability to invade or damage the host, can be primary pathogens capable of causing disease due to their presence.
    • Opportunistic bacteria: Microorganisms with low intrinsic virulence, can cause serious infection in immunocompromised individuals or in the presence of foreign bodies.

    Transmission and Entry Of Pathogens

    • Portals of entry:
      • Ingestion (e.g., Salmonella food poisoning)
      • Inhalation (e.g., Tuberculosis)
      • Penetration (e.g., HIV)
      • Sexual (e.g., Chlamydia)
      • Vertical (e.g., Group B Streptococcus)
    • Adhesion: Bacterial attachment to host cells is crucial for establishing a stable population and preventing clearance by the immune system. Adhesins, small bacterial protein ligands, recognize specific receptors on host cells.
    • Invasion: This process involves pathogens employing biochemical virulence factors called “Invasins” which can damage host cells and facilitate spread.

    Immune Evasion

    • Immune evasion: Pathogens have developed mechanisms to avoid being killed by the immune system:
      • Inhibition of phagocytosis: Capsules composed of polysaccharides can prevent phagocytosis by immune cells.
      • Survival within phagocytes: Some pathogens can escape the phagosome, prevent phagosome/lysozyme fusion, or survive within the phagolysosome.
      • Immune cell destruction/evasion: Bacteria may produce enzymes that directly target immune cells or prevent their function, such as leucocidins, streptolysin, and coagulase.

    Damage To Host Cells

    • Bacterial enzymes: These can damage host cells and are important for immune evasion. Examples include invasins, toxins, and superantigens.

    Endotoxins and Exotoxins

    • Exotoxins: Polypeptide molecules produced by living bacteria, usually secreted or released during cell lysis. They can act locally or distally and target specific cells.
    • Endotoxins: Integral parts of the bacterial cell envelope, released due to cell lysis or turnover. LPS (Lipopolysaccharide) is a prototypical example, found in Gram-negative bacteria. Endotoxins can induce a pro-inflammatory cascade leading to septic shock.

    Dissemination of Pathogens in The Body

    • Spread:
      • Through tissues or tissue planes
      • Haematogenous (bloodstream)
      • Lymphatic (lymph system)
      • Carriage within macrophages
      • Ascending/descending through a tract
    • Transmission:
      • Person-to-person by direct contact
      • Respiratory (coughing, sneezing)
      • Gastrointestinal (diarrhea)
      • Sexually (genital discharge/ulcer)
      • Vertical & perinatally

    Host Risk Factors

    • Factors increasing susceptibility to infection:
      • Extremes of age
      • Diabetes
      • Immunosuppression (disease-induced or medication-related)
      • Major breach in skin/mucosa
      • Prosthetic materials
      • Anatomical abnormality or malfunction
      • Antibiotic therapy

    Pathogenesis of Bacterial Infection

    • Pathogenesis refers to the mechanisms by which microorganisms cause disease.
    • Pathogen is a microorganism that can cause disease.
    • Pathogenicity refers to the ability of a microorganism to cause disease.
    • Virulence refers to the severity of the disease caused by a pathogen.

    Normal Flora (Microbiome)

    • The normal flora, also known as the microbiome or microbiota, are microorganisms that reside in or on our bodies without causing disease.
    • These microorganisms are mostly non-pathogenic, meaning they do not cause disease.
    • However, they can cause infection if they escape their usual location, a barrier is breached, or the host is immunosuppressed.

    Virulent Bacteria

    • Virulent bacteria possess an increased ability to invade or damage the host.
    • Primary pathogens are able to cause disease as a result of their presence within the host.
    • They may live among normal flora without causing disease in the host, in which case they are considered "colonized".
    • Virulence factors are genetic, biochemical, or structural features of a pathogen that enable or enhance its ability to produce disease.

    Opportunistic Bacteria

    • Opportunistic bacteria have low intrinsic virulence and usually do not cause infections in non-immunocompromised patients.
    • They may cause serious infections in certain circumstances, such as in immunocompromised individuals or in the presence of foreign bodies.

    Infection

    • The occurrence of an infection depends on the state of the host, the virulence of the organism, the size of the inoculum, and the portal of entry.

    Transmission of Pathogens

    • Pathogens can be transmitted through various portals of entry:
      • Ingestion: Examples include Salmonella food poisoning.
      • Inhalation: Examples include Tuberculosis.
      • Penetration: Examples include HIV.
      • Sexual: Examples include Chlamydia.
      • Vertical: Examples include Group B Streptococcus.

    Bacterial Entry and Immune Evasion

    • Bacteria utilize various mechanisms to gain entry into the body and evade the immune system:
      • Adhesion: Adhesins, small bacterial protein ligands, help establish a stable population of bacteria within the host by recognizing specific receptors on host cells.
      • Invasion: Invasins, proteins that can damage host cells and facilitate spread and invasion, help bacteria invade the host.
      • Immune Evasion: Bacteria can evade the immune system by:
        • Inhibition of phagocytosis: Capsule composed of polysaccharides prevents phagocytosis by immune cells.
        • Survival within phagocytes: Some bacteria can escape the phagosome, prevent phagosome/lysozyme fusion, or survive within the phagolysosome.
        • Immune cell destruction: Some bacteria can produce enzymes that directly target immune cells or prevent their function, such as leucocidins, streptolysin, and coagulase.

    Host Cell Damage

    • Bacteria can damage host cells through the production of enzymes and toxins:
      • Invasins: Damage host cells and facilitate spread and invasion.
      • Toxins: These are compounds that are toxic to host cells. There are two main types:
        • Endotoxins: These are integral parts of the bacterial cell envelope that are released upon cell lysis or turnover. Examples include lipopolysaccharide (LPS) found in Gram-negative bacteria.
        • Exotoxins: These are polypeptide molecules secreted by bacteria that can act locally or distally. They can be categorized as cytotoxins, neurotoxins, and enterotoxins.
      • Superantigens: These are a type of exotoxin that can hyperactivate the immune system leading to a shock syndrome.

    Spread of Pathogens within the Body

    • Pathogens can spread in the body via:
      • Spread through tissues or tissue planes
      • Haematogenous: Spread via the bloodstream.
      • Lymphatic: Spread via the lymphatic system.
      • Carriage within macrophages: Some bacteria can spread by “hiding” within macrophages.
      • Ascending/descending spread within a tract: Spread can occur within a specific tract, like the digestive system.

    Host Risk Factors

    • Certain factors can increase the susceptibility of a host to infection and increase the chances of severe infection:
      • Extremes of age: Infants and elderly individuals are more susceptible to infections.
      • Diabetes: Diabetes can impair immune function.
      • Immunosuppression: Various medical conditions or medications can suppress the immune system and increase susceptibility to infections.
      • Major breach in skin/mucosa: Surgical procedures or injuries can create an entry point for pathogens.
      • Prosthetic materials: Prosthetic devices can provide a surface for bacteria to colonize.
      • Anatomical abnormality or malfunction: Structural abnormalities or malfunctions can increase susceptibility to infections.
      • Antibiotic therapy: Antibiotics can disrupt the normal flora, allowing opportunistic bacteria to thrive.

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    This quiz covers the key concepts of bacterial pathogenesis, including definitions of pathogens, pathogenicity, virulence, and the differences between normal flora and pathogenic bacteria. Understand the mechanisms by which bacteria can cause disease and the factors that enhance their infectivity. Test your knowledge on how normal flora can become opportunistic pathogens under certain conditions.

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