Animal Drug Doxycycline Plus Tylosin-The combination of tylosin and doxycycline acts additive. Doxycycline belongs to the group of tetracyclines and acts bacteriostatic against many Gram-positive and Gram -negative bacteria like Bordetella, Campylobacter, E. coli, Haemophilus, Pasteurella, Salmonella, Staphylococcus and Streptococcus spp. Doxycycline is also active against Chlamydia, Mycoplasma and Rickettsia spp. The action of doxycycline is based on inhibition of bacterial protein synthesis. Doxycycline has a great affinity to the lungs and is therefore especially useful for treatment of bacterial respiratory infections. Tylosin is a macrolide antibiotic with a bacteriostatic action against Gram-positive and Gram-negative bacteria like Campylobacter, Pasteurella, Staphylococcus, Streptococcus and Treponema spp. and Mycoplasma.