We report results of a study carried out to investigate photodynamic effect of Touildine blue (TBO) on virulent factors secreted by Pseudomonas aeruginosa. Viability of MCF-7 cells incubated with culture supernatants of bacteria photosensitized with T130 (experimental) was found to be higher than that for MCF-7 cells incubated with culture supernatants of bacterial cells treated either with TBO in dark (control 11) or not receiving any treatment (neither TBO nor light (control 1)). Furthermore, whereas MCF-7 cells incubated with supernatants of bacteria, control I and 11, showed significant morphological alterations, no such changes were observed in MCF-7 cells incubated with supernatant of experimental cells. The activities of phospholipase C and proteases, virulent factors of P. aeruginosa, were also found to decrease on photo sensitization. These results suggest that the potency of virulent factors is reduced in cells surviving photodynamic treatment with T130 and this may have implication in treatment of infections caused by P. aeruginosa.