Oxytetracycline is an antibiotic indicated for treatment of infections caused by Gram positive and Gram negative microorganisms such as Mycoplasma pneumoniae, Pasteurella pestis, Escherichia coli, Haemophilus influenzae, and Diplococcus pneumoniae. It is used in studies on the oxytetracycline-resistance gene (otrA). Oxytetracycline hydrochloride is used to study phagosome- lysosome (P-L) fusion in P388D1 cells1 and antibiotic susceptibilities of Mycoplasma bovis isolates.