Acid Fast Bacilli MTb - Isoniazid Disk Diffusion Infected Tissue

Isoniazid (also called isonicotinyl hydrazine or isonicotinic acid hydrazide) is often abbreviated INH. Isoniazid is a first-line antituberculous medication used in the prevention and treatment of tuberculosis. It is available in tablet, syrup, and injectable forms (given intramuscularly or intravenously), available world-wide, inexpensive to produce and is generally well tolerated. Antibacterial agent used primarily as a tuberculostatic. It remains the treatment of choice for tuberculosis. A specific concentration of organism from a culture isolate is applied to an agar plate. Discs of absorbent material to which specific concentrations of antibiotic have been added are placed on the agar. The agar plate is incubated to allow the isolate to grow on the plate in the presence of the antibiotic. If the organism grows to the edge of the impregnated disc, the organism is resistant to that antibiotic. If an area surrounds the disc where growth of the organism has be inhibited, the organism may be susceptible to the antibiotic on the disc. The length of area of inhibition can be measured and compared to standards to determine if the organism is susceptible, intermediate, or resistant to the antibiotic.