antibiotic drug once commonly used in the treatment of infections caused by various bacteria, including those in the genera Rickettsia and Mycoplasma. Chloramphenicol was originally found as a product of the metabolism of the soil bacterium Streptomyces venezuelae (order Actinomycetales) and is now synthesized chemically. It achieves its antibacterial effect by interfering with protein synthesis in these microorganisms. The drug is seldom used, because of its potential toxicity and the availability of safer drugs.