Antibiotic Sensitivity disc are used to determine the effectivness of an antibiotic against a microorganism as a guide to antibiotic therapy. The disc consist of a specific concentration of an antibiotic in mcg which is tested against a microorganism of a standard density, swabbed uniformly on an appropriate media following overnight incubation. Colistin (Methane Sulphonate) is impregnated on a filter paper disc of specified concentration. Both sides of the disc are printed with CL and concentration 25 mcg for easy identification.