General Characteristics of Staphylococci
24 Questions
5 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What are the general characteristics of Staphylococcus species?

  • Gram (−) rods, motile, aerobic
  • Gram (+) cocci, spore formers, obligate anaerobes
  • Gram (+) cocci, non-motile, facultative anaerobes (correct)
  • Gram (−) cocci, non-spore formers, facultative anaerobes
  • Which of the following species is known for causing Toxic Shock Syndrome?

  • Staphylococcus haemolyticus
  • Staphylococcus aureus (correct)
  • Staphylococcus epidermidis
  • Staphylococcus saprophyticus
  • Which virulence factor produced by Staphylococcus aureus is known to cause Scalded Skin Syndrome?

  • Protein A
  • Exfoliative Toxin (correct)
  • Cytolytic Toxin
  • Enterotoxin
  • What is a notable biochemical characteristic of Staphylococcus species?

    <p>Catalase (+)</p> Signup and view all the answers

    Which environment can support the growth of Staphylococcus species?

    <p>7.5-10% NaCl</p> Signup and view all the answers

    Which specific enzyme is a virulence factor of Staphylococcus aureus and is involved in clot formation?

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

    Where is the primary reservoir for staphylococci located in humans?

    <p>Human naris</p> Signup and view all the answers

    Which of the following is NOT a characteristic of Staphylococcus aureus?

    <p>Heat labile exotoxins</p> Signup and view all the answers

    Which condition is characterized by the formation of pus-filled boils?

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

    Which Staphylococcus species is known for causing urinary tract infections in sexually active young females?

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

    What type of infections can Staphylococcus lugdunensis most commonly mimic?

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

    Which of the following best describes the cultural characteristics of Staphylococcus aureus on blood agar after 18-24 hours?

    <p>Beta hemolytic, creamy, butter-looking colonies</p> Signup and view all the answers

    What is a notable characteristic of Staphylococcus epidermidis?

    <p>Produces biofilm for adhesion</p> Signup and view all the answers

    Which enterotoxin type is NOT associated with food poisoning caused by Staphylococcus aureus?

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

    Which of the following is a common laboratory method for isolating Staphylococcus aureus?

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

    Which Staphylococcus species is commonly isolated but may have vancomycin resistance?

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

    What indicates a positive catalase test result?

    <p>Copious bubble formation</p> Signup and view all the answers

    Which test detects the ability of bacteria to convert fibrinogen to fibrin?

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

    What is the significance of observing a zone diameter greater than 10mm in the bacitracin susceptibility test?

    <p>The organism is susceptible to bacitracin.</p> Signup and view all the answers

    In the microdase test, what result indicates a positive test?

    <p>Dark blue or purple color</p> Signup and view all the answers

    What does a clear zone surrounding growth in the Dnase test signify?

    <p>The bacterium can hydrolyze DNA.</p> Signup and view all the answers

    What is required for a valid result in the tube coagulase test after initial incubation?

    <p>Leave the tube at room temperature overnight if negative</p> Signup and view all the answers

    What does growth with fermentation result in on mannitol salt agar?

    <p>Yellow halos surrounding growth</p> Signup and view all the answers

    In the novobiocin susceptibility test, what does a zone diameter less than 16mm indicate?

    <p>The organism is resistant to novobiocin.</p> Signup and view all the answers

    Study Notes

    General Characteristics of Staphylococci

    • Gram-positive cocci, appearing in pairs, tetrads, or clusters.
    • Non-motile and non-spore forming; facultative anaerobes.
    • Catalase-positive and oxidase-negative; can grow in environments with 7.5-10% NaCl.
    • Colonies are medium-sized (4-8 mm), cream, white, or light gold, with a buttery appearance.
    • Some species exhibit β-hemolytic activity.

    Clinically Significant Staphylococci Species

    • Staphylococcus aureus
    • Staphylococcus epidermidis
    • Staphylococcus saprophyticus
    • Staphylococcus lugdunensis
    • Staphylococcus haemolyticus

    Staphylococcus aureus

    Virulence Factors

    • Enterotoxins: Heat-stable toxins (A-E, G-J), associated with food poisoning.
    • Toxic Shock Syndrome Toxin-1: A superantigen, linked to menstruation-associated TSS.
    • Exfoliative Toxin: Causes Staphylococcal Scalded Skin Syndrome and Bullous Impetigo.
    • Cytolytic Toxins: Hemolysins including α, β, δ, and γ types.
    • Enzymatic Factors: Coagulase, fibrinolysin, protease, hyaluronidase, lipase, and beta-lactamase (penicillinase).
    • Protein A: Binds to the Fc portion of IgG, impeding opsonization.

    Epidemiology

    • Human colonization primarily occurs in the nasal passages, axillae, vagina, and skin.
    • Transmission occurs via direct contact with unwashed hands or contaminated surfaces.

    Infections and Associated Diseases

    • Common infections include:
      • Skin and wound infections (folliculitis, furuncles, carbuncles).
      • Staphylococcal Scalded Skin Syndrome (SSS).
      • Toxic Shock Syndrome (TSS).
      • Tenosynovitis (TEN).
      • Food poisoning due to enterotoxins.

    Staphylococcus epidermidis

    • Produces exopolysaccharide slime, enhancing adhesion to medical devices and resisting host defenses.
    • Associated diseases include healthcare-acquired UTIs and prosthetic valve endocarditis.

    Staphylococcus saprophyticus

    • Strong adherence to epithelial cells of the urogenital tract.
    • Primarily causes UTIs in sexually active young females.

    Staphylococcus lugdunensis

    • Exhibits higher virulence, mimicking S. aureus infections.
    • Carries the mecA gene for oxacillin resistance.
    • Associated infections include infective endocarditis, septicemia, and urinary tract infections.

    Staphylococcus haemolyticus

    • Common coagulase-negative staphylococci (CoNS), with some isolates showing vancomycin resistance.
    • Associated diseases include skin infections, bacteremia, endocarditis, and UTIs.

    Laboratory Diagnosis

    Isolation and Identification

    • Specimens collected: aspirates or swabs.
    • Culture media options include blood agar, colistin-nalidixic acid, phenylethyl alcohol, and mannitol salt agar.

    Cultural Characteristics

    • Staphylococci form round, smooth, white to creamy colonies on SBA after 18-24 hours.

    Key Diagnostic Tests

    • Catalase Test: Positive results show bubble formation.
    • Coagulase Test: Differentiates S. aureus (positive) from other staphylococci (negative).
    • Microdase Test: Detects oxidase enzyme presence.
    • Bacitracin and Novobiocin Susceptibility Tests: Determines susceptibility or resistance to bacitracin and novobiocin.
    • DNase Test: Checks for DNA hydrolysis capability, indicated by a clear zone.
    • Mannitol Salt Agar: Evaluates mannitol fermentation; growth with fermentation shows yellow halos, no fermentation remains pink/red.

    Antimicrobial Susceptibility

    • Testing is based on the source of the isolate and whether it is a contaminant or active pathogen.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    This quiz covers the general characteristics and clinically significant species of Staphylococcus. You'll explore their morphology, virulence factors, and pathogenic mechanisms, particularly focusing on Staphylococcus aureus. Ideal for students studying microbiology or infectious diseases.

    More Like This

    Staphylococci Group Characteristics Quiz
    10 questions
    Staphylococcus aureus characteristics
    10 questions
    Staphylococcus aureus caracteristici
    10 questions

    Staphylococcus aureus caracteristici

    SprightlyIambicPentameter avatar
    SprightlyIambicPentameter
    Use Quizgecko on...
    Browser
    Browser