The rifamycins are a group of ansamycin antibiotics produced by Amycolotopsis rifamycinia active against Gram positive and Gram-negative bacteria.The rifamycin complex (rifamycins A, B, C, D and E) was first isolated by researchers at Dow-Lepetit, Italy, in 1957. Development of the rifamycins continued over the next 10 years, culminating in the introduction of rifampicin (rifampin) in 1968. The rifamycins are potently active against mycobacteria, providing the mainstay of treatment for tuberculosis, leprosy and mycobacterium avium complex infections. The rifamycin analogue set provides a comprehensive selection of the natural product rifamycin B, its derivatives and semi-synthetic analogues, including rifampicin.