Colistin is not active against?
Colistin* It was obtained from B. colistinus .* It is active against gram-negative bacteria only; all except Proteus, Serratia and Neisseria are inhibited. * It is more potent on Pseudomonas, Salmonella and Shigella. Mechanism of action Rapidly acting bactericidal agent having a detergent-like action on the cell membrane. They have high affinity for phospholipids. It causes membrane distoion or pseudopore formation. It may also inactivate the bacterial endotoxin.
Pseudomonas aeruginosa
Serratia
Klebsiella pneumoniae
Burkholderia
Cell Wall Synthesis Inhibitors