Microbial Virulence Factors and Pathogenesis
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Questions and Answers

Opportunistic pathogens frequently cause disease in immunocompetent individuals.

False (B)

What does the term LD50 refer to?

  • The number of organisms required to kill half the hosts. (correct)
  • The number of organisms required to cause infection in half the hosts.
  • The number of organisms required to cure half the hosts.
  • The number of organisms required to cause disease in all hosts.

Which of the following is not a stage of bacterial pathogenesis?

  • Transmission
  • Adherence to mucous membranes
  • Production of antibodies (correct)
  • Evasion of host defenses

What are the two main types of inflammation caused by bacterial infection?

<p>Pyogenic inflammation and granulomatous inflammation</p> Signup and view all the answers

What is the term for human diseases where animals are the reservoir?

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

What is the primary mechanism by which bacteria adhere to human cells?

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

Coagulase is an enzyme that degrades hyaluronic acid in the subcutaneous tissue.

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

What is the process by which bacteria can evade host defenses by living within cells?

<p>Intracellular survival</p> Signup and view all the answers

Which of the following is not a mechanism used by bacteria to survive and grow intracellularly?

<p>Production of toxins (D)</p> Signup and view all the answers

Which of the following is not a feature of exotoxins?

<p>Stable at high temperatures, such as 100°C for 1 hour (A)</p> Signup and view all the answers

What is the main mechanism by which bacteria cause disease, besides the production of toxins?

<p>Invasion of tissues</p> Signup and view all the answers

Immunopathogenesis refers to the direct damaging effects of bacteria on host tissues.

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

What is the term for the time period between exposure to a pathogen and the appearance of symptoms?

<p>Incubation period</p> Signup and view all the answers

What is the term for the period during which nonspecific symptoms occur, before the characteristic features of the disease appear?

<p>Prodrome period</p> Signup and view all the answers

What is the term for the period during which an individual remains asymptomatic despite being infected with a pathogen?

<p>Subclinical infection</p> Signup and view all the answers

What is the term for individuals who continue to harbor a pathogen after recovering from an infection, potentially shedding the pathogen without exhibiting symptoms?

<p>Chronic carriers</p> Signup and view all the answers

Latent infections are characterized by persistent symptoms that can recur after periods of remission.

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

Flashcards

Pathogen

A microbe capable of causing disease.

Opportunistic Pathogen

Organisms that rarely cause disease in healthy individuals but can cause serious infections in immunocompromised patients.

Virulence

A quantitative measure of pathogenicity, indicating the number of organisms needed to cause disease.

LD50 (Lethal Dose 50)

The number of organisms required to kill 50% of the hosts.

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ID50 (Infectious Dose 50)

The number of organisms needed to cause infection in 50% of the hosts.

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Portal of Entry

The initial point where a pathogen enters the body.

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Adherence

The ability of bacteria to stick to surfaces, usually mucous membranes.

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Pili

Fibrous structures extending from bacteria that mediate attachment to host cells.

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Glycocalyx

A polysaccharide slime layer secreted by some bacteria, enhancing adherence.

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Bacterial Enzymes

Enzymes secreted by bacteria that aid in tissue invasion.

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Hyaluronidase

An enzyme that degrades hyaluronic acid in subcutaneous tissue, facilitating bacterial spread.

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Coagulase

An enzyme that accelerates fibrin clot formation, shielding bacteria from phagocytosis.

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IgA Protease

An enzyme that degrades secretory IgA, allowing bacteria to attach to mucous membranes.

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Leukocidins

Substances that can destroy neutrophils and macrophages.

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Capsule

A protective capsule surrounding bacteria that hinders phagocytosis.

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Pyogenic Inflammation

A defensive response to the presence of bacteria, involving neutrophils, antibodies, and complement.

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Granulomatous Inflammation

A defensive response to intracellular bacteria, involving macrophages and CD4-positive T cells.

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Intracellular Survival

The ability of bacteria to survive and multiply within host cells.

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Exotoxin Production

The process of releasing toxins by bacteria into the surrounding environment.

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Endotoxin Production

Toxic components of the bacterial cell wall that are released upon bacterial death.

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Immunopathogenesis

The immune response to a pathogen that causes disease symptoms, not the pathogen itself.

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Incubation Period

The time period between exposure to a pathogen and the appearance of symptoms.

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Prodrome Period

The period with nonspecific symptoms preceding the characteristic features of the disease.

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Specific Illness Period

The period when the characteristic features of a specific disease occur.

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Recovery Period (Convalescence Period)

The period of recovery and restoration of health after illness.

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Chronic Carrier

A persistent carrier state where an organism continues to grow in the host, with or without symptoms.

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Latent Infection

An infection where the pathogen remains dormant but can reactivate and cause symptoms.

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Subclinical Infection

An infection where the individual is infected but does not show any symptoms.

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Zoonoses

Diseases for which animals are the natural reservoirs of the pathogen.

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Human-to-Human Transmission

The transmission of a pathogen from one infected person to another.

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Vector-Borne Transmission

The transmission of a pathogen indirectly through a vector such as an insect.

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Animal-to-Human Transmission

The transmission of a pathogen from an animal to a human.

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Study Notes

Microbial Virulence Factors and Pathogenesis

  • A microorganism is a pathogen if it can cause disease. Some are highly pathogenic, causing disease often, while others cause it rarely.
  • Opportunistic pathogens rarely cause disease in healthy individuals but can cause serious infection in immunocompromised people.
  • Virulence is a measure of pathogenicity, quantified by the number of organisms needed to cause disease (LD50 – 50% lethal dose) or infection (ID50 – 50% infectious dose). A lower LD50/ID50 indicates higher virulence.

Stages of Bacterial Pathogenesis

  • Most bacterial infections originate from external sources, but some are caused by normal flora.
  • Transmission occurs by several routes (e.g. human to human, animal to human).
  • Infection involves several stages
    • Entry into the body
    • Evading the host's primary defenses (skin, stomach acid)
    • Adherence to mucous membranes (usually by pili)
    • Colonization by growth at the site of adherence
    • Disease symptoms caused by toxin production or invasion.
    • Host response with inflammation.
    • Progression or resolution of the disease.

Determinants of Bacterial Pathogenesis

  • Transmission: Microbes can spread through direct contact, vectors (e.g., insects), or indirect contact (e.g., contaminated food, water, or soil).
  • Adherence to Cell Surfaces: Pili or glycocalyx facilitate attachment to host cells or surfaces.
  • Invasion, Inflammation, and Intracellular Survival: Bacteria may invade tissue, trigger inflammation (pyogenic or granulomatous), or survive within host cells to evade immune responses. This survival can be aided by a variety of factors such as inhibiting lysosome-phagosome fusion or inhibiting acidification.

Toxin Production

  • Toxins are another key virulence factor that causes disease.
  • Exotoxins and endotoxins are different in their source, chemical composition, and toxicity. Exotoxins are protein-based molecules produced and secreted by bacteria. Endotoxins are part of the cell wall of certain gram-negative bacteria.

Immunopathogenesis

  • In some diseases, the immune response to the organism, not the organism itself, causes the symptoms.
    • (e.g, antibodies against the M protein of Streptococcus pyogenes cross-react with tissues, causing arthritis, carditis and chorea in rheumatic fever)

Typical Stages of an Infectious Disease

  • Incubation period: Time between exposure and symptom onset
  • Prodrome period: Time of nonspecific symptoms
  • Specific-illness period: Characteristic symptoms appear
  • Recovery period (convalescence): Symptoms resolve and health returns
  • Subclinical infections: individual infected but asymptomatic. Antibody presence indicates a prior infection.

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Microbial Virulence Factors And Pathogenesis Of Bacterial Infection PDF

Description

Explore the factors that determine microbial virulence and the stages involved in bacterial pathogenesis. Learn how pathogens cause disease, the concept of opportunistic pathogens, and the various routes of transmission. This quiz will test your understanding of these critical concepts in microbiology.

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