Abstract
In previous notes the inactivation of staphylococcus bacteriophage by methylene blue (Schultz and Krueger 1 ) and by toluidine blue (Clifton and Lawler 2 ) was reported.
Various samples of methylene blue in concentrations of 0.1 and 0.01% were mixed with antistaphylococcus bacteriophage, exposed to sunlight for different intervals of time, incubated for 24 hours at 37°C. and then tested for lytic activity. No inactivation was noted when the dye and 'phage were mixed, incubated, and tested in the dark. However, an exposure of 5 minutes, or even less than this time, to indirect sunlight before incubation resulted in complete inactivation of the bacteriophage.
When the methylene blue was added to the bacteriophage suspension in an atmosphere of nitrogen, or in a tube from which the air had been evacuated, no inactivation was noted. This was also true after 30 minutes exposure to direct sunlight and subsequent incubation of these oxygen-free systems. The leucobase of methylene blue likewise did not inactivate this bacteriophage.
Several indophenols having a higher oxidation potential than methylene blue were also tested. They are not photosensitive, did not inactivate the bacteriophage, and were reduced by other oxidizable substances present in the broth.
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