Microbiology: Streptococci Identification
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Questions and Answers

What is a key virulence factor common for adhesion associated with avium?

  • Extracellular surface protein (correct)
  • Flagella
  • Capsular polysaccharide
  • Endotoxin

    • Which disease is NOT associated with avium?

  • Nosocomial infection
  • Ureteritis
  • Tuberculosis (correct)
  • Endocarditis

    • In the Bacitracin Susceptibility test, a positive result indicates which group?

  • Group A (correct)
  • Group B
  • Beta-hemolytic Group
  • Group D

    • What does a positive CAMP reaction indicate?

    <p>Synergistic hemolysis with S. aureus</p> Signup and view all the answers

    What is indicated by a deep blue-purple color in hippurate hydrolysis?

    <p>Presence of glycine from S. agalactiae</p> Signup and view all the answers

    What does a positive PYR test result show?

    <p>Hydrolysis of L-pyrolidonyl-B-naphthylamide</p> Signup and view all the answers

    What does a blackening of agar in the bile esculin hydrolysis test indicate?

    <p>Presence of group D streptococci</p> Signup and view all the answers

    Which test specifically detects the presence of leucine aminopeptidase?

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

    What characterizes the lesions caused by carbuncles?

    <p>They are invasive lesions that develop from multiple furuncles.</p> Signup and view all the answers

    Which of the following is associated with Toxic Shock Syndrome?

    <p>Severe sepsis with chills and fever.</p> Signup and view all the answers

    What is a primary virulence factor of Staphylococcus epidermidis?

    <p>Exopolysaccharide slime or biofilm.</p> Signup and view all the answers

    What types of infections are commonly associated with Staphylococcus saprophyticus?

    <p>Honeymoon cystitis and nosocomial UTI.</p> Signup and view all the answers

    What laboratory characteristic helps differentiate Staphylococcus aureus from Staphylococcus epidermidis?

    <p>Hemolytic activity.</p> Signup and view all the answers

    What factor contributes to the antibiotic resistance of Staphylococcus haemolyticus?

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

    Which statement about bullous impetigo is correct?

    <p>It involves pustules that are larger and surrounded by erythema.</p> Signup and view all the answers

    What defines the cultural characteristics of Staphylococcus aureus?

    <p>Medium to large, smooth, creamy, and often pigmented yellow.</p> Signup and view all the answers

    What does a positive result indicate in the Bacitracin Susceptibility test?

    <p>Greater than 10mm zone of inhibition</p> Signup and view all the answers

    How can Staphylococcus aureus be differentiated from coagulase negative staphylococci?

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

    What result indicates a positive outcome in the coagulase slide test?

    <p>Appearance of white fibrin clot</p> Signup and view all the answers

    Which of the following tests can be performed to confirm the ability of an organism to hydrolyze DNA?

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

    In the context of selective media, what does growth on Colistin-Nalidixic Agar indicate?

    <p>Presence of Staphylococcus and Streptococcus</p> Signup and view all the answers

    What does a negative result in the free coagulase test indicate after the total incubation period?

    <p>No clot even after 16-20 hours</p> Signup and view all the answers

    Which method is used for detecting the hydrolysis of DNA in the DNase test using an indicator?

    <p>Methyl Green/Toluidine Blue Method</p> Signup and view all the answers

    What does partial inhibition on Phenylethyl Alcohol Agar indicate?

    <p>Presence of P. mirabilis</p> Signup and view all the answers

    What is the significance of yellow halos surrounding growth on Mannitol Salt Agar?

    <p>Indicates the ability to ferment mannitol</p> Signup and view all the answers

    How can you differentiate between S.epidermidis and S.aureus on Mannitol Salt Agar?

    <p>Growth with pink colonies indicates S.epidermidis.</p> Signup and view all the answers

    What characteristic indicates that S.epidermidis is susceptible to Novobiocin?

    <p>Zone of inhibition greater than 16mm</p> Signup and view all the answers

    What is a major virulence factor of Viridans Streptococci?

    <p>Polysaccharide capsule</p> Signup and view all the answers

    What is the main disease associated with Strep-Like Organisms, specifically nutritionally variant streptococci?

    <p>Subacute bacterial endocarditis</p> Signup and view all the answers

    Which of the following species belongs to the non-enterococci group of Group D Streptococcus?

    <p>Streptococcus gallolyticus</p> Signup and view all the answers

    What growth requirement is characteristic of nutritionally variant streptococci?

    <p>Requires vitamins like pyridoxal (B6)</p> Signup and view all the answers

    Which organism is regarded as the leading cause of adult bacterial meningitis in individuals aged 5-29?

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

    Study Notes

    Avium

    • Resists 6.05% NaCl and tests positive for PYR.
    • Common virulence factors include:
      • Extracellular surface protein, serine protease, gelatinase, cytolysins.
      • Can resist antibiotics and antimicrobial agents.
    • Associated diseases:
      • Nosocomial infections, UTIs particularly from catheterization, bacteremia in hemodialysis and surgery, and endocarditis with prosthetic heart valves.

    Laboratory Tests for Identification of Streptococci

    • Bacitracin Susceptibility Test (Taxo A)

      • Positive indicates Group A (susceptible) with zone of inhibition; negative indicates Group B (resistant).

    • Sulfamethoxazole-Trimethoprim Susceptibility Test

      • Positive shows susceptibility to 1.25 µg SXT disk with zone of inhibition; negative indicates resistance.

    • CAMP Reaction

      • Tests for synergistic hemolysis between Group B Streptococcus and β-hemolytic S. aureus.
      • Positive results show enhanced hemolysis with an arrowhead pattern; negative shows no zone of β-hemolysis.

    • Hippurate Hydrolysis

      • Detects hydrolysis of hippurate acid to benzoic acid and glycine; positive shows deep blue-purple color.

    • PYR Test

      • Tests ability to hydrolyze L-pyrolidonyl-β-naphthylamide; positive shows bright pink to red color in 5 minutes.

    • LAP Test

      • Hydrolyzes leucine-β-naphthylamide; positive shows red color within 1 minute.

    • Bile Esculin Hydrolysis

      • Ability to grow in 40% bile and hydrolyze esculin; positive yields blackening of the agar.

    Staphylococcus aureus: Associated Infections

    • Skin and Wound Infections

      • Folliculitis, furuncles (boils), and carbuncles (multiple furuncles).
      • Bullous impetigo presents as larger pustules with surrounding erythema.

    • Toxin-Mediated Infections

      • Scalded skin syndrome caused by exfoliative toxin.
      • Toxic shock syndrome presents with chills, fever, vomiting, diarrhea, hypotension, and rash.

    Other Staphylococcus Species

    • Staphylococcus epidermidis

      • Virulence factor: Exopolysaccharide slime enhances adhesion to catheters and devices.
      • Associated with nosocomial UTIs and prosthetic valve endocarditis.

    • Staphylococcus saprophyticus

      • Adheres to urogenital epithelial cells; commonly causes UTIs in sexually active young women.

    • Staphylococcus lugdunensis

      • Gene mec A for oxacillin resistance; causes endocarditis and UTIs.

    • Staphylococcus haemolyticus

      • Known for vancomycin resistance; linked to endocarditis and UTIs.

    Laboratory Diagnosis for Staphylococci

    • Isolation involves cultural characteristics:

      • S. aureus: Medium to large, creamy, beta-hemolytic, with an old sock odor.
      • S. epidermidis: Small to medium, non-hemolytic, translucent gray-white colonies.

    • Biochemical Tests

      • Coagulase Test differentiates S. aureus (positive) from coagulase-negative staphylococci.

    • Growth in CNA/PEA

      • Selective for gram-positive bacteria; growth indicates Staphylococcus/streptococcus.

    • DNAse Test

      • Detects DNA hydrolysis with clearing around colonies indicating positive results.

    • Mannitol Salt Agar

      • Tests ability to ferment mannitol; positive shows yellow halo around colonies.

    • Novobiocin Susceptibility Test

      • Differentiates coagulase-negative staphylococci; susceptibility indicated by zone of inhibition.

    Viridans Streptococci

    • Major throat flora with polysaccharide capsule aiding adhesion.
    • Associated diseases include subacute bacterial endocarditis, bacteremia, septicemia, and dental cavities.

    Nutritionally Variant Streptococci

    • Require vitamin B6 for growth; includes Abiotrophia and Granulicatella species.

    Group D Streptococcus: Non-Enterococci and Enterococci

    • Non-Enterococci: Includes S. bovis; positive in bile esculin test; linked to bacteremia and endocarditis.
    • Enterococci: Includes E. faecalis and E. faecium; significant in nosocomial infections.

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    Description

    This quiz covers laboratory tests for identifying streptococci, focusing on virulence factors and resistance patterns associated with Avium. You will explore bacitracin susceptibility, sulfamethoxazole-trimethoprim tests, and the CAMP reaction. Test your understanding of the identification and implications of these bacteria in clinical settings.

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