Abstract: The purpose of this study was to evaluate the bactericidal activity of some commercially available disinfectants against hospital bacterial isolates. The organism, Pseudomonas aeruginosa, was irradiated for 4 min for the induced mutation and the susceptibility to disinfectants like cetrimide, tincture of iodine, phenol, sodium hypochlorite, alcohol and chlorhexidine gluconate were checked against the wild type culture. The uvrB gene mutation in P. aeruginosa may lead the opportunistic pathogen to more infectious. The effect of various disinfectants varies with the type of disinfectants, dose of irradiation and density of the culture and concentration of the disinfectants. Sodium hypochlorite, alcohol, phenol had more lethal to wild type. The bactericidal effect was found to be in a range of 4-8 mg mL-1. Cetrimide had great lethality to the both wild type and irradiated one. The effect was found at 2 mg mL-1. Iodine was more effective to wild type (2 mg mL-1) but irradiated one was more resistant even in high concentrations. There was no such effect of chlorhexidine gluconate on both the strain and more growth to be occurred at high concentration. It was further confirmed that gluconate present in the disinfectant was used by the organism as a carbon source.