Effect of Ultraviolet Irradiation on Bacteriophage Active against Streptococcus Lactis

Abstract

Various factors influencing the destruction of bacteriophage, active against Streptococcus lactis, by ultraviolet light were studied. An u.-v. bulb having an output of 264 microwatts was more effective in destroying bacteriophage than a bulb having an output of 279 microwatts. Bacteriophage in a bacteria-free filtrate having a low bacteriophage titer was destroyed by u.-v. light in a shorter time than bacteriophage in filtrates having higher titers. Increasing the distance between the u.-v. bulb and the bacteria-free filtrate resulted in an increase in the time required to destroy bacteriophage in the filtrate. Bacteriophage in a thin film was more easily destroyed than bacteriophage in a thicker film, provided the thin film did not dry before the bacteriophage were destroyed. Drying appeared to make bacteriophage significantly more resistant to destruction by u.-v. light. The use of u.-v. light for the destruction of bacteriophage in commercial cheese plants appeared to be of. doubtful value because of the relatively long time required, and because of the increased resistance of dry bacteriophage.