Microbiology Flashcards: Staph Aureus
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Questions and Answers

What does Staph Aureus look like?

  • A cluster of bananas
  • A bundle of apples
  • A single grape
  • A bundle of grapes (correct)

    • Staph Aureus is gram positive.

    True

    How can we identify Staph vs Strep?

    Catalase test

    What is a catalase test?

    <p>Converts hydrogen peroxide to water</p> Signup and view all the answers

    How do we know that this Staph is Staph Aureus after a gram stain and catalase test?

    <p>Golden color when plated on Blood Agar</p> Signup and view all the answers

    Staph is beta-hemolytic.

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

    Staph Aureus ferments what?

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

    What is the main virulence factor for Staph Aureus?

    <p>Protein A</p> Signup and view all the answers

    How does Protein A bind to immunoglobulins?

    <p>At the Fc region</p> Signup and view all the answers

    What does binding at the Fc region do?

    <p>Inhibits complement binding</p> Signup and view all the answers

    Where does Staph Aureus colonize?

    <p>Nares (nose)</p> Signup and view all the answers

    What inflammatory diseases are caused by Staph Aureus?

    <p>Pneumonia, septic arthritis, abscesses, endocarditis, osteomyelitis</p> Signup and view all the answers

    When else would you see endocarditis?

    <p>IV drug users</p> Signup and view all the answers

    What is the most commonly affected valve in endocarditis?

    <p>Tricuspid valve</p> Signup and view all the answers

    What is the most common cause of osteomyelitis in adults?

    <p>Staph Aureus</p> Signup and view all the answers

    What are the toxin mediated diseases caused by Staph Aureus?

    <p>Scalded Skin Syndrome, Toxic Shock Syndrome, Food poisoning</p> Signup and view all the answers

    What is seen in Scalded Skin Syndrome?

    <p>Skin peeling</p> Signup and view all the answers

    What is the most common cause of Toxic Shock Syndrome?

    <p>Leaving a packing in too long</p> Signup and view all the answers

    What does TSST stand for?

    <p>Toxic Shock Syndrome Toxin</p> Signup and view all the answers

    What is the mechanism of Toxic Shock Syndrome?

    <p>TSST causes overactivation of T cells</p> Signup and view all the answers

    Why is Staph Aureus food poisoning rapid onset?

    <p>Because the toxin is pre-formed</p> Signup and view all the answers

    How does MRSA acquire its resistance?

    <p>By altering its PBP</p> Signup and view all the answers

    What is the treatment for MRSA?

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

    If the Staph Aureus is methicillin sensitive, what should you give?

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

    Study Notes

    Staphylococcus Aureus Overview

    • Staphylococcus aureus appears as clusters resembling grapes and produces a golden color on Blood Agar.
    • It is classified as Gram-positive, displaying violet coloration under a microscope.

    Identification Tests

    • Catalase test differentiates Staphylococcus from Streptococcus.
    • Staphylococcus aureus is identified by its golden coloration on Blood Agar and a positive coagulase test which converts fibrinogen to fibrin.

    Hemolytic Activity

    • Staphylococcus aureus is beta-hemolytic, fully breaking down red blood cells.

    Metabolism and Fermentation

    • It ferments mannitol, turning the agar yellow, characteristic of mannitol fermenters.

    Virulence Factors

    • The primary virulence factor is Protein A, which binds to the Fc region of immunoglobulins, inhibiting complement binding and preventing opsonization and phagocytosis.

    Colonization Sites

    • Commonly colonizes the nares (nostrils).

    Associated Inflammatory Diseases

    • Causes pneumonia, particularly post-viral bacterial pneumonia, and is the most common cause of septic arthritis, bad abscesses, acute bacterial endocarditis, and osteomyelitis.

    Endocarditis in Specific Populations

    • Endocarditis is frequently observed in IV drug users, with the tricuspid valve being the most affected.

    Osteomyelitis

    • Staphylococcus aureus is the leading cause of osteomyelitis in adults.

    Toxin-Mediated Diseases

    • Conditions include Scalded Skin Syndrome, Toxic Shock Syndrome (TSS), and food poisoning.

    Scalded Skin Syndrome

    • Characterized by skin peeling due to protease activity.

    Toxic Shock Syndrome Dynamics

    • Most commonly caused by leaving packing in too long, TSS is mediated by the Toxic Shock Syndrome Toxin (TSST), which acts as a superantigen, causing a cytokine storm.

    Food Poisoning Characteristics

    • Staphylococcus aureus food poisoning features rapid onset due to pre-formed toxins, with vomiting being a more common symptom than diarrhea.

    Antibiotic Resistance

    • Methicillin-resistant Staphylococcus aureus (MRSA) acquires resistance by altering its penicillin-binding protein (PBP).

    Treatment Protocols

    • MRSA is commonly treated with Vancomycin; if methicillin-sensitive, Nafcillin is the recommended treatment.

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    Description

    Test your knowledge of Staphylococcus aureus with these flashcards. Learn about its appearance, gram status, and identification techniques. Perfect for microbiology students looking to reinforce their understanding of this important bacterium.

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