Microbiology of Staphylococcus aureus
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Questions and Answers

What type of hemolysis is exhibited by Staphylococcus aureus?

  • α-hemolysis
  • γ-hemolysis
  • β-hemolysis (correct)
  • δ-hemolysis

    • Which of the following characteristics is NOT associated with Staphylococcus aureus?

  • Catalase-positive
  • Indole-positive (correct)
  • Coagulase-positive
  • Gram-positive cocci in clusters

    • What is the primary mechanism by which Staphylococcus aureus protein A contributes to its virulence?

  • Inhibiting complement activation and phagocytosis (correct)
  • Directly lysing red blood cells
  • Producing toxins that damage host cells
  • Promoting bacterial adherence to host tissues

    • What is the primary characteristic that differentiates Streptococcus pneumoniae from other viridans streptococci?

    <p>Presence of a capsule (A)</p> Signup and view all the answers

    Which of the following is a potential complication associated with Staphylococcus aureus infection?

    <p>All of the above (D)</p> Signup and view all the answers

    What is the significance of the superantigen TSST-1 produced by Staphylococcus aureus?

    <p>It binds to MHC II and the T-cell receptor, causing polyclonal T-cell activation and cytokine release (D)</p> Signup and view all the answers

    Which of the following bacterial species is NOT a β-hemolytic bacteria?

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

    Which of the following is a common site for Staphylococcus aureus colonization?

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

    Which of the following virulence factors is NOT produced by Bordetella pertussis?

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

    Which of the following is a characteristic of Haemophilus influenzae?

    <p>Requires both NAD+ and hematin for growth (D)</p> Signup and view all the answers

    Which of the following is NOT a correct association?

    <p><em>Legionella pneumophila</em> - cutaneous infections (A)</p> Signup and view all the answers

    Which of the following bacterial species is associated with cystic fibrosis?

    <p><em>Burkholderia cepacia</em> (A)</p> Signup and view all the answers

    What is the primary mode of transmission for Brucella?

    <p>Ingestion of contaminated animal products (D)</p> Signup and view all the answers

    Which of the following bacterial species is best identified using a silver stain?

    <p><em>Legionella pneumophila</em> (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the paroxysmal stage of pertussis?

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

    Which of the following treatment options is NOT commonly used for Brucella infections?

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

    What is the primary function of a transposon in bacterial genetics?

    <p>To create plasmids with multiple drug resistance (A)</p> Signup and view all the answers

    In which scenario is transposition particularly critical?

    <p>When transferring genetic material across different species (D)</p> Signup and view all the answers

    Which of the following statements about plasmids is accurate?

    <p>Plasmids can contribute to multi-drug resistance in bacteria (B)</p> Signup and view all the answers

    What is a transposon?

    <p>A segment of DNA that can copy and excise itself (B)</p> Signup and view all the answers

    What role does the target site play in the process of transposition?

    <p>It is where the transposon integrates into the DNA (C)</p> Signup and view all the answers

    Which bacteria are known for producing yellow pigments?

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

    What is the primary reason for needing to autoclave spores of certain bacteria?

    <p>Spores lack metabolic activity and are highly resistant to heat (D)</p> Signup and view all the answers

    Which species is primarily associated with dental plaques and infective endocarditis?

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

    Which bacteria are notably associated with color, specifically blue-green pigmentation?

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

    Which condition is primarily associated with P aeruginosa in patients with cystic fibrosis?

    <p>Ventilator-associated pneumonia (C)</p> Signup and view all the answers

    Which of the following bacteria form spores and are resistant to heat?

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

    What is the key characteristic of nontypeable H influenzae?

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

    Which bacterial species is responsible for gas gangrene?

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

    What is the primary mode of transmission for Haemophilus influenzae?

    <p>Through respiratory droplets (D)</p> Signup and view all the answers

    Which of the following infections is NOT caused by Neisseria gonorrhoeae?

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

    Which treatment is recommended for Neisseria gonorrhoeae if chlamydial coinfection is suspected?

    <p>Ceftriaxone plus doxycycline (A)</p> Signup and view all the answers

    What type of vaccine is used to prevent infections caused by Haemophilus influenzae type b?

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

    Which culture medium is used to identify Haemophilus influenzae?

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

    What happens to the recipient cell after it integrates new bacterial genes during high-frequency recombination?

    <p>It remains F- but may have new bacterial genes. (B)</p> Signup and view all the answers

    What is an important prophylactic treatment for contacts of someone infected with Neisseria meningitidis?

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

    What is the result of transduction related to the 'packaging' error?

    <p>Introduction of foreign DNA into a bacterial cell. (A)</p> Signup and view all the answers

    Which of the following is a characteristic of non-typeable strains of Haemophilus influenzae?

    <p>They are the most common cause of mucosal infections. (D)</p> Signup and view all the answers

    What is the main function of IgA protease produced by Haemophilus influenzae?

    <p>Destroys mucosal IgA (B)</p> Signup and view all the answers

    Which cell type receives the leading part of a plasmid and chromosomal genes during recombination?

    <p>F- cell (A)</p> Signup and view all the answers

    Which statement is true about Hfr cells during the transfer process?

    <p>Hfr cells can integrate chromosomal genes into recipient cells. (A)</p> Signup and view all the answers

    What does the integration of new bacterial genes via high-frequency recombination imply for the Hfr cell?

    <p>The Hfr cell provides gene combinations to F- cells. (A)</p> Signup and view all the answers

    During the transfer to an F- cell, what component primarily influences the genetic makeup?

    <p>Plasmid and chromosomal genes (A)</p> Signup and view all the answers

    What remains unchanged in the recipient F- cell after the integration of new genes?

    <p>The F factor status (A)</p> Signup and view all the answers

    What type of genes can be integrated into an F- cell during high-frequency recombination?

    <p>A mix of plasmid and chromosomal genes (D)</p> Signup and view all the answers

    Study Notes

    High-Yield Principles in Microbiology

    • Microbiology questions frequently require two-step processes
    • First, identify the causative organism for a clinical presentation.
    • Then, provide an answer about that specific organism or relevant antimicrobials.
    • Organisms are presented in individual "profiles" and within their respective systems of infection.
    • Memorize laboratory characteristics for quick identification of microbes.

    Bacterial Structures

    • Appendages (flagella, pili/fimbriae):

      • Flagella are proteins for motility.
      • Pili/fimbriae form during conjugation for adherence.

    • Specialized Structures (spores):

      • Spores are highly resistant to heat and chemicals, essential for survival. Core contains dipicolinic acid.

    • Cell Envelope

      • Capsule: prevents phagocytosis.
      • Slime Layer: mediates adherence, biofilm formation.
      • Outer Membrane: contains endotoxin, proteins (porins) for transport.
      • Periplasm: space between cytoplasmic and outer membrane in gram-positive bacteria.
      • Cell Wall: peptidoglycan for structural support, protects against osmotic pressure.
      • Cytoplasmic Membrane: phospholipid bilayer containing proteins for transport and other enzymatic functions.
      • Lipoteichoic Acids: found only in gram-positive bacterial cell walls.

    Stains

    • Gram Stain: used to distinguish gram-positive and gram-negative bacteria based on their cell wall structure.
    • Giemsa Stain: stains glycogen and mucopolysaccharides, diagnosing conditions like Whipple's disease.
    • Periodic Acid-Schiff (PAS) Stain: used to stain glycoproteins and mucopolysaccharides
    • Ziehl-Neelsen Stain (Acid-fast stain): designed to identify acid-fast bacteria (e.g., mycobacteria) using carbol fuchsin.
    • India Ink Stain: for detecting Cryptococcus neoformans capsules.
    • Silver Stain: highlighting specific substances or structures like Helicobacter pylori.
    • Fluorescent Antibody Stain: used to identify many bacteria, viruses, fungi.

    Special Culture Requirements

    • Specific media are required for different microbes to facilitate their growth
    • For example, H. influenzae needs factors V (NAD+) and X (hemating).
    • Different media contain varying factors to meet the needs specific micro-organisms.

    Anaerobes

    • Anaerobes are normal microbiota in the GI tract but can be pathogenic elsewhere
    • They are sensitive to oxidative damage and lack catalase/superoxide dismutase.
    • Requires specific anaerobic conditions for growth.

    Intracellular Bacteria

    • Intracellular bacteria like Rickettsia and Chlamydia live and replicate within host cells.
    • Use specific mechanisms to evade host immune responses.
    • These bacteria rely on host cellular components to survive and reproduce.

    Encapsulated Bacteria

    • Encapsulated bacteria have a polysaccharide capsule serving as an antiphagocytic virulence factor.
    • The capsules prevent phagocytosis by immune cells.
    • Vaccination against encapsulated bacteria utilizes the polysaccharide antigen.

    Urease-Positive Organisms

    • High urease activity plays a role in the development of kidney stones (eg, struvite).
    • This is due to the production of ammonia from urea, increasing pH.

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    Description

    Test your knowledge on the characteristics, virulence factors, and clinical significance of Staphylococcus aureus and related bacterial species. This quiz covers hemolysis types, complications, and differentiating traits essential for understanding bacterial pathology.

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