Cationic peptides: distribution and mechanisms of resistance.

Cationic antimicrobial peptides are observed throughout nature. In mammals they are observed both at epithelial surfaces and within the granules of phagocytic cells. They are an important component of innate defences, since in addition to their ability to kill microorganisms, they are able to modulate inflammatory responses. With respect to their ability to kill bacteria, it is very difficult to isolate resistant mutants. However there are a few known mechanisms of intrinsic resistance, including PhoPQ-dependent and other alterations in lipopolysaccharide structure that influence self promoted uptake, and protease-mediated resistance.