Water disinfection using visible light-active photocatalyst has recently attracted more attention due to its potential to inactivate microbes. In this study we have investigated the efficiency of photocatalysis (TiO / UV) on the inactivation of and the attenuation of its virulence factors. For this aim, the photocatalytic effects of TiO / UV on the cultivability and viability of were investigated. Furthermore, during the photocatalysis, the morphology of the bacterial cells was examined by atomic force microscopy (AFM) while the virulence factors were assessed by protease and lipase activities in addition to the mobility and communication of cells. The results revealed that during the photocatalysis the bacterial cells lost their cultivability and viability on agar under the action of the reactive oxygen species generated by the photocatalytic reaction. In addition, AFM observations have shown a damage of the bacterial membrane and a total disruption of the bacterial cells. Moreover, the major virulence factors such as biofilm, lipase and protease expression have been markedly inhibited by TiO / UV treatment. In addition, the bacteria lost their ability of communication "quorum sensing" and mobility with twitching and swarming types after 60 min of photocatalytic treatment. Accordingly, TiO / UV is an effective method to reduce virulence and to prevent biofilm formation.