Pyrazomycin is an antibiotic produced by Str. candidus NRRL 3601. In the culture of monolayer cells, the minimum inhibitory concentration of vaccinia virus is 2 μg/mL, which can also inhibit measles and herpes simplex. In mice, intraperitoneal, subcutaneous, oral and skin application can reduce the pathological changes of vaccinia. Pyrazomycin is a competitive inhibitor of pyrimidine nucleoside metabolism.