Questions and Answers
What is a key virulence factor common for adhesion associated with avium?
Which disease is NOT associated with avium?
In the Bacitracin Susceptibility test, a positive result indicates which group?
What does a positive CAMP reaction indicate?
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What is indicated by a deep blue-purple color in hippurate hydrolysis?
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What does a positive PYR test result show?
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What does a blackening of agar in the bile esculin hydrolysis test indicate?
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Which test specifically detects the presence of leucine aminopeptidase?
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What characterizes the lesions caused by carbuncles?
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Which of the following is associated with Toxic Shock Syndrome?
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What is a primary virulence factor of Staphylococcus epidermidis?
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What types of infections are commonly associated with Staphylococcus saprophyticus?
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What laboratory characteristic helps differentiate Staphylococcus aureus from Staphylococcus epidermidis?
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What factor contributes to the antibiotic resistance of Staphylococcus haemolyticus?
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Which statement about bullous impetigo is correct?
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What defines the cultural characteristics of Staphylococcus aureus?
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What does a positive result indicate in the Bacitracin Susceptibility test?
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How can Staphylococcus aureus be differentiated from coagulase negative staphylococci?
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What result indicates a positive outcome in the coagulase slide test?
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Which of the following tests can be performed to confirm the ability of an organism to hydrolyze DNA?
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In the context of selective media, what does growth on Colistin-Nalidixic Agar indicate?
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What does a negative result in the free coagulase test indicate after the total incubation period?
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Which method is used for detecting the hydrolysis of DNA in the DNase test using an indicator?
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What does partial inhibition on Phenylethyl Alcohol Agar indicate?
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What is the significance of yellow halos surrounding growth on Mannitol Salt Agar?
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How can you differentiate between S.epidermidis and S.aureus on Mannitol Salt Agar?
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What characteristic indicates that S.epidermidis is susceptible to Novobiocin?
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What is a major virulence factor of Viridans Streptococci?
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What is the main disease associated with Strep-Like Organisms, specifically nutritionally variant streptococci?
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Which of the following species belongs to the non-enterococci group of Group D Streptococcus?
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What growth requirement is characteristic of nutritionally variant streptococci?
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Which organism is regarded as the leading cause of adult bacterial meningitis in individuals aged 5-29?
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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
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Bacitracin Susceptibility Test (Taxo A)
- Positive indicates Group A (susceptible) with zone of inhibition; negative indicates Group B (resistant).
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Sulfamethoxazole-Trimethoprim Susceptibility Test
- Positive shows susceptibility to 1.25 µg SXT disk with zone of inhibition; negative indicates resistance.
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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.
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Hippurate Hydrolysis
- Detects hydrolysis of hippurate acid to benzoic acid and glycine; positive shows deep blue-purple color.
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PYR Test
- Tests ability to hydrolyze L-pyrolidonyl-β-naphthylamide; positive shows bright pink to red color in 5 minutes.
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LAP Test
- Hydrolyzes leucine-β-naphthylamide; positive shows red color within 1 minute.
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Bile Esculin Hydrolysis
- Ability to grow in 40% bile and hydrolyze esculin; positive yields blackening of the agar.
Staphylococcus aureus: Associated Infections
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Skin and Wound Infections
- Folliculitis, furuncles (boils), and carbuncles (multiple furuncles).
- Bullous impetigo presents as larger pustules with surrounding erythema.
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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
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Staphylococcus epidermidis
- Virulence factor: Exopolysaccharide slime enhances adhesion to catheters and devices.
- Associated with nosocomial UTIs and prosthetic valve endocarditis.
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Staphylococcus saprophyticus
- Adheres to urogenital epithelial cells; commonly causes UTIs in sexually active young women.
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Staphylococcus lugdunensis
- Gene mec A for oxacillin resistance; causes endocarditis and UTIs.
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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.
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Biochemical Tests
- Coagulase Test differentiates S. aureus (positive) from coagulase-negative staphylococci.
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Growth in CNA/PEA
- Selective for gram-positive bacteria; growth indicates Staphylococcus/streptococcus.
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DNAse Test
- Detects DNA hydrolysis with clearing around colonies indicating positive results.
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Mannitol Salt Agar
- Tests ability to ferment mannitol; positive shows yellow halo around colonies.
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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.
