Staphylococci

Morphology

  • Gram Positive Cocci
  • Non-motile
  • Non-spore forming
  • Arranged in irregular clusters
    • Pairs, chains, grapes

Culture

  • Grow on most media in aerobic conditions
    • Staphylococcus aureus is golden
    • Staphylococcus epidermidis is white
  • Resistant to drying & heat

Resistance

  • To many anti-microbials
    • ß-lactamase production
      • Plasmid mediated
      • Resistant to some Penicillins & Cephalosporins
    • Methicillin Resistance
      • Independent of ß-lactamase production
      • Mechanism unknown
      • Function of cell wall structure
  • Tolerance
    • Inhibition without death
    • Due to lack of activation of autolytic enzymes (PBP) in cell wall

Toxins & Enzymes

  • Exotoxin
    • Alpha-haemolysin
    • ß-haemolysin
    • Endotoxin C
    • Are haemolytic & pyogenic
  • Enterotoxin
    • Food poisoning
    • Protein that clots citrated plasma
    • S Aureus produces it » Coagulase Positive
    • S Epidermidis doesn’t » Coagulase Negative
    • Synonymous with invasive potential
  • Other
    • Hyaluronidase
    • Staphylokinase
    • Exfoliative toxin
    • “Toxic Shock Syndrome” toxin

Pathogenesis

  • Staphylococcus aureus
    • Pathogenic & invasive
  • Staphylococcus epidermidis
    • Found on skin
    • Rarely suppurative
    • May infect prostheses

Pathology

Staphylococci, gram stain of staphylococcus aureus showing clusters of gram positive cocci
Gram stain of Staphylococcus aureus showing clusters of Gram positive cocci. Image by Dr Graham Beards, Wikimedia Commons, CC BY-SA 4.0.
  • Abscess
    • Prototype infection
      • Furuncle, carbuncle, pimple
    • Focal suppuration & necrosis
    • Coagulase coagulates fibrin around lesion to produce wall
    • Liquefaction of necrosis occurs

Treatment

  • Made difficult by
    • Resistance to AB
    • Hypovascular abscess
    • Biofilm with biomaterials
  • Drainage of pus important » Key
  • Most staphylococci are Penicillin resistant
  • Many are Flucloxacillin resistant
  • All are sensitive to Vancomycin
    • Except USA

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.