Staphylococcus species

General Properties of ALL Staphylococci

  • Gram staining properties:

    • Gram positive cocci in clusters  

      • DDx: Gram positive cocci in chains = Streptococcus species.

      • DDx: Gram positive cocci in tetrads = Micrococcus species.

 

  • Special Lab Tests:

    • Catalase positive (ALL)

      • DDx: Catalase negative = Streptococcus species.

    • Facultative Aerobe (ferments glucose, prefers oxygen)

    • Coagulase testing

      • Positive

        • S. aureus

        • **S. lugdunensis (is POS in SLIDE coag testing, but NEG in TUBE coag testing)

      • Negative

        • All other staphylococcus (commonly referred to as Coag-negative staph)

 

 

Staphylococcus aureus 

  • Unique Identifying Feature:

    • Coagulase positive (all other staph are negative)

    • Turns the pink media yellow on agar plate

 

  • Virulence factors:

    • Protein A

    • Capsular polysaccharides

    • Coagulase enzyme

    • Toxins (TSST-1, enterotoxins)

    • Hemolysins

      • NOTE: S. haemolyticus also has hemolytic properties, but is COAG NEGATIVE

 

  • Clinical Presentation & Diseases:

    • Toxic shock syndrome (TSST-1 toxin)

    • Scalded skin syndrome (SSS)- due to Exfoliatin

    • Soft tissue infections- due to Panton Valentine Leukocidin (PVL)

    • Food poisoning- Enterotoxins

    • Bacteremia & Endocarditis

 

  • Methicillin Resistant Staph Aureus (MRSA) 

    • Virulence factors: Altered penicillin binding protein (PBP) produced by the  mecAgene .

 

Staphylococcus epidermidis 

  • General Features:

    • Most frequently isolated (often a contaminant)

 

  • Virulence factors:

    • Produces extracellular slime layer (biofilm)

 

  • Clinical Presentation & Diseases:

    • Endocarditis, particularly prosthetic valves

 

Staphylococcus saprophyticus 

  • Unique Identifying Feature:

    • Differentiation from other staph organisms= Novobiocin resistant

      • Most other Staph are susceptible to Novobiocin

 

  • Clinical Presentation & Diseases:

    • Acute UTI in young, sexually active women

      • 2nd most common cause of cystitis

 

Staphylococcus  haemolyticus

  • Virulence factors:

    • Has hemolytic properties

      • Do NOT confuse with S. aureus which is COAGULASE POSITIVE

    • Is intrinsically resistant to Vancomycin

      • Do NOT confuse with Vancomycin resistant Enterococcus (VRE) which is gram pos cocci in CHAINS (Strep species).

 

  • Clinical Presentation & Diseases:

    • Line related sepsis

 

Staphylococcus  lugdunensis

  • General Features:

    • Is Coagulase positive on the SLIDE, but Coagulase negative in the TUBE Testing

    • PYR reaction differentiates it from S. aureus

 

 

DIFFERENTIAL DIAGNOSIS

Staphylococcus species

  • General Features:

    • Gram positive cocci in chains/pairs  

  • Lab Tests:

    • Catalase NEGATIVE

 

Micrococcus species

  • General Features:

    • Gram positive cocci in tetrads

    • Normal flora of skin and mucous membranes

      • Rarely causes infection, so don't confuse with Staph!! 

  • Lab Tests:

    • Microdase test + (modified oxidase reaction)

    • Forms yellow colonies (similar to Staph aureus)

    • Does NOT ferment glucose (staph does)

 

Rothia mucilaginosa (formerly Stomatococcus mucilaginosus)

  • General Features:

    • Large Gram positive cocci in pairs or clusters

    • Normal flora of skin and oral cavity

    • Pathogen in patients with underlying malignancy/ bone marrow transplant

      • Central lines

      • Endocarditis

      • Bacteremia 

  • Lab Tests:

    • Colonies are sticky or mucoid, white and adherent to the agar

​​

Staphylococcus aureus

      (& Methicillin Resistant Staph Aureus)

​​​Staphylococcus epidermidis 

​​​Staphylococcus saprophyticus 

​​​Staphylococcus haemolyticus 

​​​Staphylococcus lugdunensis ​​​

MICRO & IMMUNO 

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