Tylosin has a wide spectrum of activity against gram positive bacteria including Staphylococci, Streptococci, Corynebacteria, and Erysipelothrix. It has a much narrower gram negative spectrum of activity, but has been shown to be active against Campylobacter coli, and certain spirochaetes.It has also been shown to be extremely active against Mycoplasma species isolated from both mammalian and avian hosts.