• Gram positive cocci arranged in clusters (hence "cocci")
• Form colonies - golden, white colonies
• Type by bacteriophage (bacterium-specific virus)

• Gram positive cocci arranged in chains or pairs
• Transparent colonies
• Typed by API strips

By presence of absence of coagulase

1. Coagulase positive
   • Staph aureus
2. Coagulase negative
   • Staph epidermidis
   • Staph saprophyticus 

By type of haemolysis on culture on blood-agar plate

1. Partial haemolysis - alpha: strep pneumoniae
2. Complete haemolysis - Beta: strep pyogenes (causes erysipelas/nec fasc)
3. No haemolysis - Gamma: enterococci

By Lancefield group antigens

• Group A: Strep pyogenes
• Group B: none (strep agalactiae)
• Group C: none (strep equisimilis)
• Group D: enterococcus faecalis
• Group F: Viridans group