Immune System and Infections Overview
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What is the primary form of fungi that consists of filamentous units?

  • Pseudohyphae
  • Dimorphic mold
  • Yeast
  • Mycelium (correct)

    • Which of the following molds only exists in the mold form?

  • Histoplasma
  • Coccidioides
  • Blastomyces
  • Aspergillus (correct)

    • What term describes the ability of dimorphic molds to switch between two forms based on temperature?

  • Form conversion
  • Phase variation
  • Thermal dimorphism (correct)
  • Morphological fluctuation

    • What is often considered the gold standard for diagnosing fungal infections?

    <p>Culture, smear, or histology</p> Signup and view all the answers

    Which of these fungi is considered endemic to the Southwest US?

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

    In diagnosing fungal infections, which of the following methods are known to suffer from sensitivity and specificity issues?

    <p>Serology and antigen detection methods</p> Signup and view all the answers

    Which type of parasite is Plasmodium classified as?

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

    Which of the following is NOT a category of parasites?

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

    What is the primary characteristic that distinguishes helminths from protozoan parasites?

    <p>Helminths are multicellular</p> Signup and view all the answers

    What is the common name for the disease caused by Coccidioides?

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

    What are pseudohyphae most commonly associated with?

    <p>Candida albicans</p> Signup and view all the answers

    Which of the following correctly defines thermal dimorphism?

    <p>Conversion between hyphal and yeast forms based on temperature</p> Signup and view all the answers

    What is generally regarded as a limitation of serology in diagnosing fungal infections?

    <p>It often suffers from variable sensitivity and specificity.</p> Signup and view all the answers

    Which protozoan is primarily responsible for malaria?

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

    What is an example of a multicellular parasite?

    <p>Ascaris lumbricoides</p> Signup and view all the answers

    Which fungi are likely to cause disease when exposed to higher temperatures inside the human body?

    <p>Dimorphic molds</p> Signup and view all the answers

    Which of the following correctly categorizes ectoparasites?

    <p>Multicellular organisms that live on a host</p> Signup and view all the answers

    What is a common symptom of the primary infection caused by Coccidioides?

    <p>Community-acquired pneumonia resemblance</p> Signup and view all the answers

    What is the primary issue with culturing fungal organisms?

    <p>It can be difficult and requires specific, enriched media.</p> Signup and view all the answers

    What is a key distinction between protozoan and helminth parasites?

    <p>Protozoans are unicellular, while helminths are multicellular.</p> Signup and view all the answers

    What type of clinical illness is primarily caused by Rotavirus in children?

    <p>Severe acute enteritis</p> Signup and view all the answers

    Which virus class is associated with both mosquito transmission and a variety of clinical syndromes?

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

    What significant risk was identified in the long-term studies of the Rotavirus vaccines?

    <p>Increased risk of intussusception</p> Signup and view all the answers

    Which virus is known for its association with neonatal microcephaly?

    <p>Zika virus</p> Signup and view all the answers

    Which viral family includes Poliovirus and Hepatitis A virus?

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

    What type of virus is known for causing severe gastroenteritis outbreaks commonly referred to as 'cruise-ship' disease?

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

    Which of the following viruses is transmitted via mosquito and can lead to encephalitis?

    <p>Rubella virus</p> Signup and view all the answers

    Which HSV variant is most commonly associated with causing cold sores?

    <p>HSV 1</p> Signup and view all the answers

    What severe condition can occur due to HSV 2 transmission during birth?

    <p>Severe neonatal HSV disease</p> Signup and view all the answers

    Which virus reactivates to cause shingles?

    <p>Varicella-zoster virus</p> Signup and view all the answers

    Which immune cells are primarily targeted by Epstein-Barr Virus during infection?

    <p>B-lymphocytes</p> Signup and view all the answers

    What is a common outcome of congenital Cytomegalovirus infection in infants?

    <p>Sensorineural hearing loss</p> Signup and view all the answers

    What serological response occurs first during an Epstein-Barr Virus infection?

    <p>Viral capsid antigen response</p> Signup and view all the answers

    What is the primary infectious unit of a virus referred to as?

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

    What type of toxins are secreted by bacteria and categorized based on their toxic effects?

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

    Which type of virus relies on hijacking the host cell machinery for replication?

    <p>All viruses</p> Signup and view all the answers

    Which category of viral genomes includes both single-stranded and double-stranded forms?

    <p>DNA virus</p> Signup and view all the answers

    What is a key aspect of the immune response to viral infections?

    <p>T-cell proliferation and differentiation</p> Signup and view all the answers

    How can viruses contribute to mutation and evolution?

    <p>Viruses can undergo rapid mutations and genetic recombination.</p> Signup and view all the answers

    What is the primary role of positive single-stranded RNA in viral replication?

    <p>It is directly translated to proteins.</p> Signup and view all the answers

    Which factor significantly contributes to viral pathogenesis during infection?

    <p>The immune response of infected individuals.</p> Signup and view all the answers

    What process allows viruses to evade immune responses by changing their antigenic appearance?

    <p>Antigenic drifting and shifting.</p> Signup and view all the answers

    What role does RNA polymerase play in the replication of negative single-stranded RNA viruses?

    <p>It transcribes the viral genome segments to mRNA.</p> Signup and view all the answers

    What does the term 'viral quasispecies' refer to?

    <p>Variants generated from high mutation rates during viral replication.</p> Signup and view all the answers

    What is the function of DNA-dependent RNA polymerase II in DNA viruses?

    <p>Synthesizes mRNA from the viral DNA.</p> Signup and view all the answers

    Study Notes

    Immune System Impacts

    • Issues with the innate immune system can stem from impaired anatomical barriers or deficiencies in the adaptive immune system.
    • Nutritional status influences immune function, primarily through protein deficiency, which affects T-cell function.
    • Insufficient protein leads to increased susceptibility to infections including tuberculosis and disseminated Herpes infections.
    • During pregnancy, risk for infections does not increase in the first trimester, but susceptibility rises as pregnancy progresses due to reduced T-cell, natural killer, and B-cell activity.

    Co-morbidities and Infections

    • Clinical infections often relate to situational factors such as diabetes or the use of immunosuppressive drugs (e.g., corticosteroids, chemotherapy).
    • Conditions like surgical incisions or implanted foreign bodies also create infection risk.

    Bacterial Characteristics

    • Bacteria are classified by shape: spherical (coccus), rod-shaped (bacillus), or curved (spirillum/spirochete/vibrio).
    • Bacterial cell walls consist of peptidoglycan, which influences Gram staining properties; Gram-positive bacteria appear purple, while Gram-negative bacteria appear red-pink.
    • Bacteria can utilize oxygen, leading to the production of toxic molecules (H2O2, O2-); obligate aerobes need oxygen, whereas microaerophilic bacteria tolerate some oxygen.

    Bacterial Pathogenesis and Toxins

    • Bacteria produce enzymes (urease, catalase, coagulase) that enhance their pathogenicity.
    • Endotoxins are structural components of the bacterial cell wall; lipopolysaccharide (LPS) triggers inflammatory responses.
    • Exotoxins are secreted proteins classified as:
      • Protein synthesis inhibitors
      • Neurotoxins
      • Super-antigens
      • cAMP inducers
      • Cytolysins

    Viruses

    • Viruses are the smallest (20-300 nm) infectious agents, consisting of nucleic acid (DNA or RNA) encased in a protein shell, sometimes with a lipid envelope.
    • Viruses hijack host cell machinery for replication; the infectious unit is termed a virion.
    • Viral classification is based on nucleic acid type, capsid symmetry, and presence of an envelope.

    Notable Viral Infections

    • Measles: Characterized by cough, coryza, conjunctivitis, and a rash; complications include severe CNS disease and SSPE.
    • Mumps: Resurgent mainly on college campuses; similar vaccination concerns as measles.
    • Ebola and Marburg: Cause hemorrhagic syndromes with high fatality rates and pose risks especially to healthcare workers.

    Fungal Infections

    • Fungi are eukaryotic with cell walls of polysaccharides and ergosterol; significant targets for antifungal therapies.
    • Pathogenic fungi are divided into yeasts (single-celled), dimorphic molds (change morphology based on environment), and monomorphic molds (fixed form).
    • Coccidioidomycosis, endemic in the Southwestern US, usually presents as asymptomatic pneumonia; culture and serological tests are essential for diagnosis.

    Parasitology

    • Parasites, eukaryotic organisms that derive nutrients from hosts, are categorized into protozoan (unicellular), helminths (multicellular), and ectoparasites (arthropods).
    • Key differences exist between protozoan and helminthic parasites, reflecting their biological and pathogenic complexities.

    Viral Structure and Replication

    • DNA can be single-stranded, linear double-stranded, or circular double-stranded.
    • Viral replication involves producing structural proteins/enzyme and replicating the viral genome.
    • The primary objective of viruses is to synthesize mRNA, with positive single-stranded RNA acting as infectious mRNA, directly translated into proteins.
    • Negative single-stranded RNA and double-stranded RNA viruses require viral RNA polymerase for mRNA transcription, while DNA viruses use host DNA-dependent RNA polymerase II.

    Pathogenic Factors and Viral Evolution

    • Viruses attach to host cells to inject nucleic acids for replication, leading to multiple copies and potential immune responses.
    • Immune responses during and after infection are key contributors to viral pathogenesis.
    • Antigenic drifting and shifting allow viruses to evade immune responses, due to rapid evolution and high mutation rates during replication.
    • Viral quasispecies emerge from variant genomes forming population structures, influenced by mutations, recombination, and reassortment.

    DNA Viruses Overview

    • Herpes Viruses:
      • HSV-1: Causes cold sores and can lead to severe CNS infections like HSV encephalitis.
      • HSV-2: Primarily causes genital disease; can lead to severe neonatal infections.
    • Varicella-zoster virus: Causes chickenpox and shingles (dermatomal distribution).
    • Epstein-Barr Virus: Responsible for infectious mononucleosis, targeting B-lymphocytes; follows a specific serological response pattern.
    • Cytomegalovirus: Another cause of mononucleosis, significant congenital infections and hearing loss.

    Commonly Relevant Viruses

    • Coronaviruses: Known for mild respiratory illnesses and severe diseases like SARS and COVID-19, which emerged in late 2019.
    • Influenza Viruses: Types A and B cause severe illness, subject to antigenic drift and shift, leading to annual epidemics.
    • Parainfluenza Viruses: Associated with croup; notable for causing severe airway obstruction.
    • Respiratory Syncytial Virus (RSV): Major cause of bronchiolitis in infants; monoclonal antibody therapy available.
    • Measles Virus: Notable for classic symptoms (cough, coryza, conjunctivitis) and risks of complications like SSPE.
    • Mumps Virus: Similar resurgence patterns as measles; vaccine may be ineffective due to waning immunity.
    • Ebola and Marburg Viruses: Cause hemorrhagic syndromes with high fatality rates, transmissibility through body fluids.

    Fungi Characteristics

    • Fungi are eukaryotic, characterized by cell walls containing polysaccharides and ergosterol.
    • Pathogenic fungi categorized into yeasts, dimorphic molds, and monomorphic molds.
    • Yeasts are unicellular; some can form pseudohyphae (e.g., Candida albicans).
    • Dimorphic molds change form based on temperature (environmental vs. human body).
    • Coccidioidomycosis (“Valley Fever”) is endemic in the Southwest U.S., often asymptomatic.

    Diagnosing Fungal Infections

    • Diagnoses rely on culture, smear, histology from biopsies, and serological tests.
    • Fungal cultures require specific media, with variable sensitivity and specificity for serology and antigen tests.

    Parasitology Basics

    • Parasitology studies eukaryotic pathogens distinct from fungi, involving organisms living off hosts.
    • Parasites classified into:
      • Protozoa (unicellular, e.g., Plasmodium)
      • Helminths (multicellular, e.g., flatworms, roundworms)
      • Ectoparasites (arthropods, e.g., ticks, lice, fleas)
    • Understanding differences between protozoan and helminth parasites is crucial.

    Viral Structure and Replication

    • DNA can exist in multiple forms: single-stranded, linear double-stranded, or circular double-stranded.
    • Viruses replicate through two main processes: production of structural proteins and enzymes, and replication of the viral genome.
    • The primary goal of viruses is to generate mRNA for protein synthesis during their replication cycle.
    • Positive single-stranded RNA is directly infectious and translated to proteins, while negative single-stranded RNA requires a viral RNA polymerase for transcription.
    • DNA viruses use host-cell enzymes (DNA-dependent RNA polymerase II) to produce mRNA.

    Viral Pathogenesis

    • Viruses attach to host cells, inserting nucleic acids, which can trigger an immune response leading to pathogenesis.
    • Antigenic drift and shift allow viruses to evade immune detection by altering their antigenic structure.
    • High mutation rates during replication contribute to the formation of viral quasispecies.
    • Viral evolution can occur through mutations, recombination, and reassortment.

    Bacterial Enzymes and Toxins

    • Bacteria produce various enzymes (e.g., urease, catalase, coagulase) that contribute to their pathogenicity.
    • Endotoxins are structural components (e.g., lipopolysaccharides) that induce inflammatory responses, potentially leading to shock.
    • Exotoxins are secreted by bacteria and classified into categories based on their effects, including:
      • Protein synthesis inhibitors
      • Neurotoxins
      • Super-antigens
      • cAMP inducers
      • Cytolysins

    Characteristics of Viruses

    • Viruses are the smallest infectious agents (20-300 nm) and contain either DNA or RNA encased in a protein shell (capsid), which may be surrounded by a lipid envelope.
    • Viruses lack the machinery for independent replication and depend entirely on host cells for propagation.
    • The basic classification of viruses includes their nucleic acid type (DNA or RNA), capsid symmetry, presence of an envelope, and virion dimensions.

    Overview of DNA Viruses

    • Herpes Viruses:
      • HSV 1: Commonly causes oral diseases (cold sores) and can lead to encephalitis.
      • HSV 2: Primarily causes genital disease and can result in severe neonatal infections.
      • Varicella-zoster virus: Causes chickenpox and shingles, with lesions noted in a dermatomal distribution upon reactivation.
      • Epstein-Barr Virus: Associated with infectious mononucleosis, targeting B-lymphocytes, with distinct serological responses.
      • Cytomegalovirus: Causes infectious mononucleosis and is a leading cause of congenital infections and childhood hearing loss.

    Overview of Positive-Strand RNA Viruses

    • Rotavirus: Known for severe gastroenteritis in children, associated with vaccines that increased intussusception risk.
    • Caliciviruses (noroviruses): Cause gastroenteritis outbreaks, notoriously linked to cruise ships.
    • Picornaviruses: Include Poliovirus, Human Rhinovirus (common cold), Hepatitis A (fecal-oral transmission), and Enteroviruses with milder illness profiles.
    • Flaviviruses: Include Hepatitis C, Yellow Fever, Dengue, St. Louis Encephalitis, West Nile, and Zika, with many transmitted by mosquitoes and causing various syndromes.
    • Togaviruses: Includes Rubella (German Measles), Eastern and Western Equine Encephalitis, and Chikungunya, with several transmitted by mosquitoes, linked to distinct clinical manifestations.

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    Description

    Explore the intricate relationship between the immune system and various infections in this quiz. Understand how nutritional status, co-morbidities, and bacterial characteristics influence immune function and susceptibility to infections. Delve into the details of innate and adaptive immune responses and their clinical implications.

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