Increasing number of multi resistant Gram-negative bacteria has become a major problem worldwide. Depending on our studies performed before two years that recorded a high susceptibility of Klebseilla spp and Pseudomonas aeruginosa to colistin, we completed this study to evaluate the antibacterial activity of colistin against of various gram negative bacteria. In this study, male 100 (81%) while female 24 (19%). Highest bacterial infection isolate was between 21-40 years followed by 41-63 years. Highest bacterial isolate from swab 73 (59%) followed by catheter tip 38 (31%). Klebseilla spp, Acinetobacter spp recorded high sensitive to colistin 33 (27%) equally and pseudomonas spp 23 (19%). The resistant was observed with proteus spp 3 (2%) followed by providencia. Improved understanding of the pharmacokinetics and pharmacodynamics of colistin and its methanesulphonate will let the design of suitable administer medicine procedures for make the most of efficiency although decreasing toxicity and the expansion of resistance.