Microbiology: Staphylococcus Species Overview
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Questions and Answers

Which of the following Staphylococcus species are facultative anaerobes?

  • Staphylococcus xylosus (correct)
  • Staphylococcus warneri (correct)
  • Staphylococcus saprophyticus
  • Staphylococcus aureus spp. aureus (correct)

    • Which Staphylococcus species is considered the most virulent?

  • Staphylococcus cohnii
  • Staphylococcus lugdunensis
  • Staphylococcus saprophyticus
  • Staphylococcus aureus (correct)

    • Which of these species are classified as obligate anaerobes?

  • Staphylococcus lugdunensis
  • Staphylococcus warneri
  • Staphylococcus saccharolyticus (correct)
  • Staphylococcus saprophyticus

    • Which of the following characteristics is true for Micrococcus species?

    <p>They are skin-colonizing organisms.</p> Signup and view all the answers

    Which Staphylococcus species is resistant to Novobiocin?

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

    What type of colonies do Staphylococcus species form after 18-24 hours of incubation?

    <p>Circular, opaque, smooth</p> Signup and view all the answers

    Which of the following statements is incorrect regarding Staphylococcus species?

    <p>Staphylococcus lugdunensis is not associated with human infections.</p> Signup and view all the answers

    What describes the primary requirement for obligate anaerobes?

    <p>They can only grow in the absence of oxygen.</p> Signup and view all the answers

    What characteristic distinguishes Staphylococcus aureus from Streptococcus in laboratory tests?

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

    What type of pigment do isolated colonies of Staphylococcus aureus produce?

    <p>Golden-yellow pigment</p> Signup and view all the answers

    On which agar medium does Staphylococcus aureus grow particularly well?

    <p>Nutrient Agar and Sheep's Blood Agar</p> Signup and view all the answers

    What is the significance of the yellow pigment produced by Staphylococcus aureus?

    <p>Acts as a virulence factor</p> Signup and view all the answers

    What is a primary test used to differentiate Staphylococcus from other organisms?

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

    Which property of Staphylococcus aureus is indicative of its ability to thrive in aerobic environments?

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

    Why is Staphylococcus aureus considered a significant pathogen in microbiology?

    <p>It can produce various toxins and has a high level of antibiotic resistance</p> Signup and view all the answers

    What component of blood agar allows for the differentiation of hemolytic bacteria such as S. aureus?

    <p>Presence of blood cells</p> Signup and view all the answers

    What is the primary reason plasma is preferred over serum for the coagulase test?

    <p>Plasma includes clotting factors that serum lacks.</p> Signup and view all the answers

    What can cause false positive results in the slide test for coagulase?

    <p>High salt content in the media used for testing.</p> Signup and view all the answers

    Which Staphylococcus species is particularly mentioned as producing the clumping factor?

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

    Why should organisms not be picked from Mannitol Salt Agar for the coagulase test?

    <p>It may cause errors due to salt content.</p> Signup and view all the answers

    What percentage of strains reportedly produce the clumping factor?

    <p>10% to 15%</p> Signup and view all the answers

    Which component of plasma is crucial for performing the coagulase test?

    <p>Fibrinogen.</p> Signup and view all the answers

    What is the first step in performing the tube coagulase test?

    <p>Emulsifying colonies in plasma.</p> Signup and view all the answers

    What should not be performed with organisms taken from high salt media?

    <p>Coagulase testing on slide.</p> Signup and view all the answers

    What enzyme is primarily associated with positive coagulase test results?

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

    Which genus is primarily identified through the coagulase test?

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

    What type of coagulase is detected using the slide test?

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

    What should be avoided when performing the coagulase test to prevent false positives?

    <p>Transferring blood agar to the slide</p> Signup and view all the answers

    What happens if Staphylococcus strains produce fibrinolysin during the coagulase test?

    <p>Clots dissolve after 4 hours of incubation</p> Signup and view all the answers

    What is the incubating time recommended for the coagulase test?

    <p>1-4 hours</p> Signup and view all the answers

    Which of the following conditions can lead to false (+) results in the coagulase test?

    <p>Using EDTA plasma</p> Signup and view all the answers

    What is one of the key laboratory tests performed to detect coagulase activity?

    <p>Slide test</p> Signup and view all the answers

    Why is it important to avoid high salt concentrations in the media for coagulase testing?

    <p>It causes auto agglutination</p> Signup and view all the answers

    What is the role of coagulase in Staphylococcus aureus?

    <p>To bind plasma fibrinogen and cause clotting</p> Signup and view all the answers

    How can the presence of clumping factor affect the coagulase test results?

    <p>It can lead to true positive results</p> Signup and view all the answers

    What is the main distinguishing feature of coagulase-positive Staphylococcus species?

    <p>They produce coagulase</p> Signup and view all the answers

    Which of the following statements is true regarding the coagulase test?

    <p>It can provide false results if not performed correctly</p> Signup and view all the answers

    What is the significance of observing ocular conditions during the coagulase test?

    <p>It avoids auto agglutination</p> Signup and view all the answers

    What is the primary purpose of the thermostable DNase test?

    <p>To identify staphylococcal enterotoxin in milk</p> Signup and view all the answers

    Which is a benefit of using thermostable DNase over tube coagulase testing?

    <p>It is quicker for direct detection of Staphylococcus aureus</p> Signup and view all the answers

    What is the purpose of the lysostaphin disk in this procedure?

    <p>To determine susceptibility of bacteria to lysostaphin</p> Signup and view all the answers

    What indicates a positive reaction in the lysostaphin susceptibility test?

    <p>Marked decrease in turbidity compared to negative control</p> Signup and view all the answers

    What incubation temperature is recommended for the bacterial suspensions?

    <p>35-37 C</p> Signup and view all the answers

    Why is the first suspension shaken vigorously during the process?

    <p>To ensure even distribution of lysostaphin</p> Signup and view all the answers

    What characteristic distinguishes Staphylococcus spp. regarding lysostaphin susceptibility?

    <p>They possess an interpeptide bridge consisting of glycine-rich peptides</p> Signup and view all the answers

    What is a sign of resistance in Micrococcus spp. during the lysostaphin test?

    <p>Suspension remains turbid</p> Signup and view all the answers

    How long should the lysostaphin test suspensions incubate before comparison?

    <p>2 hours</p> Signup and view all the answers

    What indicates susceptibility to lysostaphin?

    <p>Complete clearing of bacterial suspension</p> Signup and view all the answers

    Which of the following describes lysostaphin's function?

    <p>It cleaves peptide linkages in bacterial cell walls</p> Signup and view all the answers

    What is the expected turbidity result for a negative control suspension?

    <p>Turbidity remains unchanged</p> Signup and view all the answers

    Why is the addition of a negative control suspension important?

    <p>To serve as a comparison for the test suspension</p> Signup and view all the answers

    What soil type is used for colony formation in this procedure?

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

    Study Notes

    Staphylococci Overview

    • Includes facultative anaerobes that can grow in the presence or absence of oxygen, such as Staphylococcus aureus, S. lugdunensis, S. saprophyticus, and S. shield.
    • Obligate anaerobes grow exclusively in oxygen-free environments.
    • S. aureus is recognized as the most virulent species among staphylococci and is a common source of food poisoning.

    Staphylococcus Characteristics

    • Colonies typically grow circular, opaque, and smooth after 18-24 hours of incubation on blood agar.
    • S. aureus colonies produce a distinctive golden-yellow pigment due to staphyloxanthin.
    • Common culture media for S. aureus includes Nutrient Agar and Sheep's Blood Agar.

    Catalase and Coagulase Tests

    • Staphylococci are catalase positive, differentiating them from streptococci.
    • Coagulase test is critical for identifying S. aureus, as it produces coagulase, leading to clot formation in plasma.
    • Two types of coagulase are produced: bound (clumping factor) and free coagulase.

    Coagulase Test Procedure

    • The slide test detects bound coagulase; a bacterial colony is mixed with plasma to check for clumping.
    • Tube coagulase test involves emulsifying colonies in plasma and observing for clot formation after incubation.

    Results Interpretation

    • Positive coagulase indicates S. aureus, while some S. saprophyticus strains may also produce clumping factors.
    • False positives can arise from auto-agglutination or if colonies are from high salt environments (e.g., Mannitol Salt Agar).

    Sources of Error

    • Some Staphylococcus strains may produce fibrinolysin, which could dissolve clots if incubated longer than four hours.
    • Media with high salt concentrations can lead to misleading positive results.

    Thermostable DNase and Lysostaphin Testing

    • Thermostable DNase is effective for rapidly screening for staphylococcal enterotoxins in dairy products.
    • Lysostaphin is an endopeptidase that targets specific peptide linkages in Staphylococcus cells, rendering susceptible strains vulnerable to osmotic lysis.
    • Micrococcus species resist lysostaphin due to the absence of the glycine-rich interpeptide bridge.

    Summary of Cultural Characteristics

    • S. aureus grows well on various media and can be identified by pigment production and colony morphology.
    • Routine testing for coagulase is essential for distinguishing pathogenic strains in laboratory settings.

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    Description

    This quiz explores various species of Staphylococcus, including their anaerobic and facultative anaerobic growth requirements. Test your knowledge on Staphylococcus aureus, Staphylococcus lugdunensis, and other related species. Perfect for students studying microbiology or related fields.

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