Which of the following drugs is effective against pseudomonas infection?

Polymyxin 8 and Colistin Polymyxin and colistin were obtained in the late 1940s from Bacillus polymyxa and B. colistinus respectively. They are active against gramnegative bacteria only; all except Proteus, Serratia and Neisseria are inhibited. Both have very similar range of activity, but colistin is more potent on Pseudomonas, Salmonella and Shigella. Mechanism of action They are rapidly acting bactericidal agents; have a detergent-like action on the cell membrane. They have high affinity for phospholipids: the peptide molecules (or their aggregates) orient between the phospholipid and protein films in gram-negative bacterial cell membrane causing membrane distoion or pseudopore formation. As a result ions, amino acids, etc. leak out. Sensitive bacteria take up more of the antibiotic. They may also inactivate the bacterial endotoxin. They exhibit synergism with many other AMAs by improving their penetration into the bacterial cell. ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:734