Novobiocin is a narrow-spectrum antimicrobial that may be bacteriostatic or bactericidal at higher concentrations. It is active mostly against gram-positive bacteria but also against a few gram-negative bacteria. There is a synergistic effect with tetracyclines. Many species of bacteria can develop resistance to novobiocin. Adverse reactions are quite frequent after administration. Novobiocin is labeled for intramammary treatment of staphylococcal mastitis in cattle, for administration PO in dogs, and as a medicated feed for treatment of fowl cholera and susceptible staphylococcal infections in turkeys, chickens, ducks, and mink.