Resistance of selected strains of Pseudomonas aeruginosa to low-intensity ultraviolet radiation.

The resistances of 10 strains of Pseudomonas aeruginosa and other microorganisms to an ultraviolet (UV) intensity of 100 muW/cm2 were determined. Organisms were exposed in 2- or 15-ml saline suspensions contained in uncapped polyethylene bottles for increasing periods of time, and the surviving fractions were enumerated. Decimal reduction times were calculated by regression analysis, using the least-squares method. The 10 strains of P. aeruginosa, compared with Micrococcus radiodurans and Candida albicans, were very susceptible to low-intensity UV radiation. Results from this study showed that a UV intensity of 100 muW/cm2 penetrated saline suspensions up to 40 mm deep sufficiently to kill high levels of microbial cells, especially P. aeruginosa cells. These results allowed us to design a system for determining and monitoring the sterilization capability of low-intensity UV radiation. In our particular case, UV proved to be an efficient mode for sterilizing saline suspensions of P. aeruginosa in polyethylene bottles. The significance and application of these findings with regard to supporting UV as a sterilant are discussed.