It is a tetracycline antibiotic produced by Streptomyces str.rim ο SUS. There are many producing bacteria, such as str.gilvus, str.albus, str.capuensis, str.capuensis, str.utilis, etc. It has anti - gram-positive bacteria and negative bacteria, mycobacterium action. It also inhibits mycoplasma rickettsiae chlamydia spirochetes and some protoplasms. It is cross-resistant to tetracycline and aureomycin, and partly resistant to chloramphenicol. See tetracycline for mechanism of antibacterial action and drug resistance.