Described herein are methods of inhibiting the growth of or killing abacterium in an animal subject, preventing ordelaying onset of an infection with a bacterium in an animal subject,preventing or delaying onset of a pathogen mediated diseaseor disorder in an animal subject, or reducing bacterial load in an animalsubject, comprising administering an effective amount ofa derivatized chitosan to the animal. Also described herein are preparationscomprising a chitosan derivative for administration toan animal.
