Pathophysiological Concepts Chapter 8: Infection & Defects in Mechanisms of Defence

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Questions and Answers

What characterizes an immune deficiency?

An exaggerated response to infections

An inappropriate response to self-cells

An overreaction to beneficial foreign tissues

A range from mild defects to life-threatening severity (correct)

Which of the following best defines communicability?

The ability of a pathogen to survive within the host

The means by which a pathogen enters the host

The capacity of a pathogen to cause severe disease

The ability of an infectious agent to spread between individuals (correct)

What is the role of toxigenicity in a pathogen?

It is a measure of the pathogen's ability to invade tissues

It refers to the production of soluble toxins or endotoxins (correct)

It indicates how easily a pathogen spreads

It determines the pathogen’s ability to cause disease

How does virulence differ from pathogenicity?

Virulence measures severity while pathogenicity refers to the ability to produce disease Signup and view all the answers

Which of the following is NOT a factor for infection?

Antigenicity Signup and view all the answers

Staphylococcus aureus is classified as an opportunistic pathogen because it:

Takes advantage of weaknesses in the host’s defense mechanisms Signup and view all the answers

What does pathogenicity refer to in a pathogenic agent?

Ability to cause disease Signup and view all the answers

Which routes of entry can pathogenic microorganisms use to infect a host?

Any possible route including bites of animals or insects Signup and view all the answers

What is a primary consequence of bacterial endotoxins released into the bloodstream?

Activation of complement and clotting systems Signup and view all the answers

Which of the following pathogens is most commonly associated with bacteremia?

Gram-negative bacteria Signup and view all the answers

What is a distinguishing feature of viral replication?

Viruses require a permissive host cell to replicate Signup and view all the answers

Which mechanism allows a virus like the herpes virus to remain dormant?

Latent infection until reactivation Signup and view all the answers

What type of toxins are primarily responsible for causing fever and the inflammatory response?

Endotoxins Signup and view all the answers

Which statement about influenza is true?

Influenza viral surface antigens can change over time Signup and view all the answers

What characteristic of viruses makes them fundamentally different from bacteria regarding reproduction?

Viruses require a host cell for replication Signup and view all the answers

What type of disease is primarily caused by viral infections such as the common cold?

Self-limiting acute infections Signup and view all the answers

Which of the following best describes exotoxins?

Enzymatic toxins that damage host cells Signup and view all the answers

What is the primary mode of transmission for viral diseases like AIDS?

Sexual contact Signup and view all the answers

What type of hypersensitivity reaction is commonly associated with asthma due to bronchial constriction?

Type I hypersensitivity Signup and view all the answers

Which of the following is NOT a clinical finding associated with Systemic Lupus Erythematosus (SLE)?

Urticaria (hives) Signup and view all the answers

What is the role of RhoGAM in preventing hemolytic disease of the newborn?

It prevents Rh-negative mothers from creating antibodies against Rh-positive fetuses. Signup and view all the answers

Which mechanism of hypersensitivity is characterized by an immediate reaction due to a pre-existing-antibody?

Hyperacute rejection Signup and view all the answers

What factors are considered when determining a highly active antiretroviral therapy (HAART) regimen for HIV treatment?

Secondary clinical symptoms, viral load, and past treatment history Signup and view all the answers

What term describes a minor change in the virus leading to yearly vaccines with different strains?

Antigenic drift Signup and view all the answers

Which of the following is true about Candida albicans?

It is a common cause of fungal infections. Signup and view all the answers

How does the body primarily control fungal infections?

Via phagocytes and T lymphocytes Signup and view all the answers

What is the primary mode of transmission for parasitic infections?

Through vectors or ingestion Signup and view all the answers

What is the main goal of active immunization?

To induce long-lasting protective immune responses Signup and view all the answers

What is considered a localized infection caused by Candida albicans?

Thrush in the mouth lining Signup and view all the answers

Which of the following is NOT a countermeasure against infectious microorganisms?

Herd immunity Signup and view all the answers

In which type of environment do fungal infections typically adapt to survive?

Wide temperature variations and low oxygen levels Signup and view all the answers

What secondary effect is commonly associated with parasitic infections?

Direct tissue damage from the parasite itself Signup and view all the answers

What percentage of the population is generally needed to achieve herd immunity?

85% Signup and view all the answers

What defines primary immune deficiency?

Genetic defects present at birth Signup and view all the answers

Which of the following is a clinical presentation of immunodeficiency?

Unusual or recurrent severe infections Signup and view all the answers

What is a primary treatment for immunodeficiencies?

Gamma-globulin therapy Signup and view all the answers

Which cells does HIV primarily target in the immune system?

CD4+ T-helper cells Signup and view all the answers

What is the most common route of HIV transmission worldwide?

Heterosexual activity Signup and view all the answers

What condition results from the continuous suppression of immune responses due to HIV?

Acquired Immune Deficiency Syndrome (AIDS) Signup and view all the answers

In the context of HIV, what does a serologically negative individual indicate?

They are free from HIV infection Signup and view all the answers

What differentiates secondary immunodeficiencies from primary immunodeficiencies?

Secondary deficiencies result from other underlying conditions Signup and view all the answers

What is a key immunological finding in individuals with AIDS?

Decreased CD4+ T-cell count Signup and view all the answers

Which therapy is used to manage HIV and prevent its progression to AIDS?

Antiviral agents Signup and view all the answers

Study Notes

Mechanisms of Immune Response

Immune deficiency results in increased susceptibility to infections, ranging from mild to life-threatening.
Hypersensitivity responses can be exaggerated against environmental substances (allergies), misdirected against self-cells (autoimmunity), or directed against beneficial tissues (alloimmunity).

Infection Factors

Communicability: Ability of a pathogen to spread; highly communicable diseases include measles and pertussis, while HIV is less so.
Infectivity: Capacity of a pathogen to invade and multiply in the host; e.g., Herpes simplex can remain latent.
Virulence: The severity of disease caused by a pathogen; rabies virus is highly virulent, while measles shows low virulence.
Pathogenicity: Ability to produce disease influenced by communicability, infectivity, virulence, and extent of tissue damage (e.g., HIV's effect on T cells).
Portal of Entry: Routes include direct contact, inhalation, ingestion, or bites from animals/insects.
Toxigenicity: Ability to produce toxins that enhance virulence.

Bacterial Diseases

Bacteria are prokaryotic organisms; environmental or immune factors influence their survival.
Staphylococcus aureus: Opportunistic pathogen, leading to skin infections, abscesses, or septicemia; antibiotic resistance is a concern (e.g., MRSA).

Toxins

Exotoxins: Enzymes damaging host cell membranes or inhibiting protein synthesis.
Endotoxins: Trigger inflammatory responses and fever, often released by Gram-negative bacteria leading to conditions like sepsis and cardiovascular shock.

Viral Diseases

Viruses are the most common human afflictions; replication relies on host cell infection.
Spread via aerosol, blood, sexual contact, or vectors.
Viral replication involves host cell attachment, penetration, uncoating, replication, assembly, and release.
Some viruses (e.g., herpes) can remain latent within the host.

Influenza Variability

Undergoes antigenic variation necessitating annual vaccinations.
Minor changes are termed antigenic drift; major changes are referred to as antigenic shift.

Fungal Infections

Eukaryotic organisms existing as yeasts or molds; pathogenicity involves environment adaptation and immune suppression.
Candida albicans: Common opportunistic pathogen, found in normal microbiomes; can cause localized or disseminated infections, leading to complications like thrush.

Parasitic Infections

Ranges from unicellular protozoa to multicellular worms; common in developing countries.
Damage may arise from infestation and inflammatory responses.

Countermeasures Against Infections

Infection control, antimicrobials, active immunization (vaccines), and passive immunotherapy are vital for managing infections.

Active Immunization

Vaccines stimulate protective antibodies or cellular immunity without causing disease.
Goal is to induce long-lasting immunity and achieve herd immunity (85% vaccination rate increases public protection).

Immunodeficiencies

Primary: Congenital genetic defects affecting immune function.
Secondary: Acquired conditions like infections, cancer, or aging leading to increased infection susceptibility.
Clinical signs include recurrent severe infections and specific immune cell deficiencies.

Evaluation of Immunity

Complete blood count (CBC) provides cellular information; quantitative immunoglobulin testing screens for antibody levels.

Treatment for Immunodeficiencies

Options include gamma-globulin therapy, stem cell transplants, transfusions, and gene therapy.

HIV and AIDS

AIDS is a secondary immune deficiency caused by HIV, which targets CD4+ T-helper cells.
HIV leads to a decreased T-cell count, resulting in a generalized immune deficiency.
New treatments allow for better management of HIV, turning it into a chronic illness rather than a terminal condition.

Epidemiology of AIDS

Transmitted via blood, IV drug use, sexual contact, or maternal transmission.
Over half of those living with HIV/AIDS are women, with heterosexual activity being the most common transmission pathway.

Clinical Manifestations of AIDS

Presentation includes serologically negative or positive states, early stages of HIV disease, or full-blown AIDS.
Early symptoms are typically mild (headache, fever, fatigue) but worsen with disease progression.

Treatment and Prevention of HIV and AIDS

Highly active antiretroviral therapy (HAART) involves combinations of medications tailored to individual patients.
Long-term use of these therapies can elevate risks for cardiovascular and metabolic conditions.

Hypersensitivity

Characterized by an altered immune response resulting in host damage; classified into allergies, autoimmunity, and alloimmunity.

Types of Hypersensitivity

Four mechanisms:
- Type I: IgE mediated (common allergies)
- Type II: Tissue-specific reactions
- Type III: Immune complex mediated
- Type IV: Cell-mediated

Type I Hypersensitivity

Immediate allergic reactions mediated by IgE against environmental antigens.
Symptoms include asthma, hives, and gastrointestinal disturbances.
Treatment options include avoidance of allergens and antihistamines.

Autoimmunity

Characterized by a breakdown of tolerance leading to the immune system misidentifying self-antigens as foreign.
Can be triggered by infectious diseases.

Example of Autoimmune Disease

Systemic Lupus Erythematosus (SLE): Autoimmune condition with multisystem involvement; symptoms include butterfly rash, arthritis, and presence of antinuclear antibodies.

Alloimmunity

Immune responses against tissue from another individual, observable in transfusions and transplants.
ABO Blood Group: Type O is a universal donor; Type AB is a universal recipient.
Rh incompatibility can lead to hemolytic disease of the newborn; RhoGAM injections prevent complications during pregnancy.

Transplant Rejection

Classified by timing:
- Hyperacute: Immediate, rare rejection due to pre-existing antibodies.
- Acute: Cell-mediated response to unmatched human leukocyte antigens.
- Chronic: Develops over months/years due to weak immune reactions against minor HLA differences.

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Description

This quiz explores key concepts in microbiology related to immune deficiencies, pathogen characteristics, and infection factors. Participants will assess their understanding of terms like communicability, virulence, and toxigenicity, as well as specific pathogens such as Staphylococcus aureus.