Abstract
The inactivation of staphylococcus bacteriophage by methylene blue was reported by Schultz and Krueger. 1 Further tests in this laboratory with various samples of methylene blue∗ have given practically the same results, concentrations of 0.05% of the dye inactivating the bacteriophage within 24 hours. In higher dilutions longer periods of time were required for inactivation, whether the tests were carried out at room temperature or at 37°C. In only a few isolated cases was an inactivation obtained with concentrations below 0.005%, when the ordinary bacteriophage suspensions were used or when such suspensions were diluted 1-10 with Martin's broth.
Similar tests have been carried out with various other dyes including toluidine blue, methylene violet, methylene green, methylene azur, thionin, eosin B, and phenol red. These dyes were added in relatively high concentrations to bacteriophage filtrates which were then incubated at 37.°C. for 24 hours or longer and tested for lytic activity. Of the series tested in this way only one, toluidine blue, served to inactivate the staphylococcus bacteriophage.
Several individual samples of the same brand of toluidine blue† have given results which in all respects were similar to those obtained with methylene blue. When incompletely inactivated dye-phage mixtures were plated out with susceptible organisms a diminution in the number of plaques was noted, both in the case of methylene blue and of toluidine blue.
Tests were made with the dye-phage mixtures which were incubated in an atmosphere of hydrogen, nitrogen, or oxygen. The results obtained were identical with those described above, while controls incubated under the same conditions retained their lytic activity.
Inactivation was not obtained with either methylene blue or toluidine blue when added to an anti-coli bacteriophage.
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