S. aureus on Baird-Parker agar with egg yolk-potassium tellurite emulsion plates (Bio-Rad), incubated at 35 } 1°C for 24 to 48 h and typical colonies (black surrounded by clear zones) were tested for coagulase activity using rabbit plasma (Biokar Diagnostics, France) after activation by overnight incubation in Brain Heart broth (Biokar Diagnostics, France) at 35°C.