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




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 ​​​





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These posts contain high yield information collected from various educational resources including textbooks, journal articles, educational websites and more. They are intended for educational use only and should NOT be taken as medical advice. I strongly believe the spreading of knowledge and depth of learned information should be encouraged in today's society rather than coveted. Membership is required to view these posts  and should be used solely for educational purposes only.