Staphylococcus Species and Infections
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Staphylococcus Species and Infections

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Questions and Answers

What is the primary purpose of the slide coagulase test?

  • To detect bound coagulase in Staphylococcus species (correct)
  • To identify the species of Streptococcus
  • To differentiate S.aureus from coagulase negative staphylococci
  • To detect the presence of free coagulase

    • What should be done if the slide coagulase test result is negative?

  • Proceed to tube coagulase testing (correct)
  • Perform the Novobiocin Susceptibility Test
  • Conduct a Gram stain for further identification
  • Re-test with a different bacterial colony

    • What is one advantage of the slide coagulase test?

  • It is a rapid diagnostic method (correct)
  • It provides a definitive identification of S.aureus
  • It can differentiate all species of staphylococci
  • It is more accurate than tube coagulase testing

    • What is the incubation temperature for the tube coagulase test?

    <p>37°C</p> Signup and view all the answers

    Which of the following is a disadvantage of the slide coagulase test?

    <p>It is less accurate than tube coagulase testing</p> Signup and view all the answers

    What is transferred into the tube during the tube coagulase test?

    <p>Reconstituted plasma</p> Signup and view all the answers

    What is the arrangement of Staphylococcus spp. cells?

    <p>Grape-like clusters</p> Signup and view all the answers

    Which characteristic is NOT associated with Staphylococcus spp.?

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

    What kind of infections can Staphylococcus aureus cause?

    <p>Suppurative infections</p> Signup and view all the answers

    What is a defining feature of Staphylococcus spp. regarding temperature resistance?

    <p>Can withstand 500°C for 30 minutes</p> Signup and view all the answers

    Which term describes the presence of Staphylococcus aureus on the skin?

    <p>Normal flora</p> Signup and view all the answers

    What is the typical appearance of non-bullous impetigo caused by Staphylococcus aureus?

    <p>Honey-colored crusts on red skin</p> Signup and view all the answers

    Which species is commonly associated with folliculitis?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    Which environment can Staphylococcus spp. tolerate?

    <p>9% NaCl</p> Signup and view all the answers

    What is the typical cause of bullous impetigo?

    <p>Autoimmune disease</p> Signup and view all the answers

    What type of infection is primarily caused by Staphylococcus aureus?

    <p>Pyogenic skin and soft tissue infections</p> Signup and view all the answers

    Which Staphylococcus species is most commonly associated with catheter-related bloodstream infections?

    <p>Staphylococcus epidermidis</p> Signup and view all the answers

    What characterizes a furuncle?

    <p>It is deeper and more extensive than folliculitis.</p> Signup and view all the answers

    What is a defining feature of a carbuncle?

    <p>It involves multiple furuncles affecting a broader area.</p> Signup and view all the answers

    What type of colony does Staphylococcus species form on culture?

    <p>Round, raised, smooth, and shiny colonies</p> Signup and view all the answers

    Which Staphylococcus species is a part of the normal flora in women and often causes UTIs?

    <p>Staphylococcus saprophyticus</p> Signup and view all the answers

    At what temperature do Staphylococcus species grow fastest?

    <p>37C</p> Signup and view all the answers

    Which of the following is a superficial infection of the skin that is often caused by Staphylococcus aureus?

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

    Which Staphylococcus species is most commonly associated with acute osteomyelitis?

    <p>Staphylococcus lugdunensis</p> Signup and view all the answers

    What type of formation surrounds pus in an abscess?

    <p>Fibrous tissue wall</p> Signup and view all the answers

    What is the principle behind the catalase test?

    <p>Production of water and oxygen from hydrogen peroxide</p> Signup and view all the answers

    Which of the following organisms is catalase positive?

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

    What indicates a positive catalase test result?

    <p>Bubbling or effervescence</p> Signup and view all the answers

    What type of coagulase is detected by the slide coagulase test?

    <p>Bound coagulase</p> Signup and view all the answers

    What is required to form staphylothrombin in the presence of free coagulase?

    <p>Coagulase-reacting factor (CRF)</p> Signup and view all the answers

    What happens during the catalase test when hydrogen peroxide is added?

    <p>Oxygen is released causing bubbling</p> Signup and view all the answers

    What differentiates staphylococci from streptococci in testing?

    <p>Production of catalase</p> Signup and view all the answers

    Which type of test detects free coagulase?

    <p>Tube coagulase test</p> Signup and view all the answers

    What is a key characteristic of coagulase-negative staphylococci (CoNS)?

    <p>Catalase positive</p> Signup and view all the answers

    What does cell wall bound coagulase react with during the slide coagulase test?

    <p>Fibrinogen in plasma</p> Signup and view all the answers

    What is the pigment produced by Staphylococcus aureus that contributes to its golden yellow colonies?

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

    What is the primary reason Staphylococcus aureus turns mannitol salt agar from red to yellow?

    <p>Fermentation of mannitol</p> Signup and view all the answers

    Which type of agar allows the differentiation of Staphylococcus aureus based on DNAse production?

    <p>DNAse agar</p> Signup and view all the answers

    What is a characteristic feature of Staphylococcus aureus colonies on blood agar?

    <p>Golden yellow colonies with beta-hemolysis</p> Signup and view all the answers

    Which virulence factor of Staphylococcus aureus protects it from phagocytosis by forming a fibrin clot?

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

    What property of Staphylococcus aureus distinguishes it from Staphylococcus epidermidis on DNAse agar?

    <p>Ability to produce DNAse</p> Signup and view all the answers

    Which statement accurately describes cellulitis caused by Staphylococcus aureus?

    <p>It does not show distinct margin around the affected area.</p> Signup and view all the answers

    What is one of the biochemical tests that Staphylococcus aureus is positive for?

    <p>Catalase activity</p> Signup and view all the answers

    What color indicates a positive result for the fermentation of mannitol on mannitol salt agar?

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

    Study Notes

    Staphylococcus Species

    • Staphylococcus are gram-positive bacteria arranged in grape-like clusters. They are non-motile, non-spore forming and ferment carbohydrates to produce lactic acid.
    • Staphylococcus species are relatively resistant to drying and heat, able to withstand 50°C for 30 minutes.
    • These bacteria are halo tolerant and can live in environments with up to 9% NaCl.
    • Some Staphylococcus are normal flora of the skin and mucous membranes.
    • Staphylococcus aureus is found on the skin, in the nostrils, and armpits.
    • Staphylococcus species can cause suppurative (pus-forming) infections and septicemia.

    Common Suppurative Infections caused by Staphylococci

    • Folliculitis: Superficial infection involving the hair follicle.
    • Furuncle/Boil: Deeper than folliculitis, more extensive, and more painful, but centers around the hair follicle.
    • Abscess: Have a wall formation around the pus.
    • Carbuncle: Accumulation of boils/furuncles.
    • Erysipelas: Superficial layer of the skin is affected. There is a layer that is "pushed up".
    • Cellulitis: Deeper layer of the skin is affected. No pushing up of the skin. Margin of the involved area is less distinct.

    Clinically Important Staphylococcus Species

    • Staphylococcus aureus: Causes pyogenic skin and soft tissue infections, pneumonia, bacteremia, infective endocarditis, and toxin-mediated illnesses.
    • Staphylococcus epidermidis: Infections from skin contamination and implants/prosthetic materials (CRBSI, prosthetic and native valve endocarditis).
    • Staphylococcus lugdunensis: Infection from skin contamination and implants, native valve endocarditis, and osteomyelitis.
    • Staphylococcus saprophyticus: Urinary tract infections (UTIs) in young women. Part of the normal flora in women.

    Staphylococcus Species on Culture

    • Staphylococcus species grow fastest at 37°C but produce pigment best at room temperature (20-25°C).
    • They form round, raised, smooth, shiny colonies.
    • Staphylococcus lugdunensis, Staphylococcus epidermidis, and Staphylococcus saprophyticus produce cream to whitish-grey colonies.
    • Staphylococcus aureus can produce golden yellow colored colonies due to a pigment known as staphyloxanthin.

    Staphylococcus aureus on Culture

    • Staphylococcus aureus can produce cream or golden yellow colonies on nutrient agar.
    • Staphylococcus aureus turns red agar to yellow due to the fermentation of mannitol on mannitol salt agar.
    • Staphylococcus aureus produces a halo of clear beta-hemolysis on blood agar plates.
    • Staphylococcus aureus is the only species possessing DNAse, which can be observed on DNAse agar.

    Staphylococcus aureus Virulence Factors

    • Catalase: Protects intraphagocytic microbes by destroying hydrogen peroxide produced by the phagocyte.
    • Coagulase: Formation of fibrin clot around the bacteria likely protects it from phagocytosis and can function as a biofilm scaffold.
    • Hyaluronidase: Spreading factor; allows dissemination of bacteria through tissue.

    Catalase Testing Differentiates Staphylococci and Streptococci

    • All staphylococcal species give a positive catalase test, which differentiates them from streptococci.

    • The production of water and oxygen from hydrogen peroxide through the enzyme catalase is the principle behind the test.

    • A positive result is observed as bubbling or effervescence due to the release of oxygen from hydrogen peroxide.

    Coagulase Testing Differentiates Staphylococcus aureus from Coagulase-Negative Staphylococci

    • Coagulase is an enzyme-like protein that causes plasma to clot by converting fibrinogen to fibrin.
    • Staphylococcus aureus produces two types of coagulase: bound coagulase and free coagulase.
    • Bound Coagulase: Cell wall-bound coagulase, also known as clumping factor, is detected by the slide coagulase test.
    • Free Coagulase: Detected by the tube coagulase test. Requires the presence of a coagulase-reacting factor (CRF) to form staphylothrombin, which reacts with fibrinogen to form a fibrin clot.

    Slide and Tube Coagulase Testing

    • Slide Coagulase Test: Detects bound coagulase.

      • Add one drop of heavy bacterial suspension and one drop of plasma to a clean slide.
      • Mix well and observe for clumping, clotting, agglutination, or coagulation after ten seconds.
      • Advantages: Rapid diagnosis.
      • Disadvantages: Less accurate.

    • Tube Coagulase Test: Detects free coagulase.

      • Transfer 0.5 mL of reconstituted plasma into the test tube.
      • Select 2-3 isolated colonies of bacteria to be tested.
      • Emulsify the bacteria in the plasma and place the tubes in the incubator at 37°C.
      • Note the time the test was started.

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    Description

    This quiz explores Staphylococcus species and their characteristics, including their structure and resistance. It also covers common suppurative infections caused by these bacteria, such as folliculitis, boils, and abscesses. Test your knowledge on this important topic in microbiology and infectious diseases.

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