Biofilm producing strains, response of S. aureus against antibiotics and haemolytic strains. A, arrows point out different kinds of biofilm: yellow arrow, no biofilm; blue arrow, weak biofilm; green arrows, moderate biofilm; black arrow, strong biofilm. B, zone of inhibitions produced by antibiotics against S. aureus (yellow arrows, zones of inhibition). C, haemolysis on blood agar produced by S. aureus (yellow arrow, partial haemolysis).