Inactivation of Staphyloccus Bacteriophage by Methylene Blue.

Abstract

Recently, one of us 1 described the trypsin susceptibility of 2 races of staphylococcus bacteriophages, a property which stands in striking contrast to the marked resistance offered to this enzyme by bacteriophages generally. It occurred to us to compare these 2 races of bacteriophage with a number of other races in our possession, as to their susceptibility to other chemical agents, particularly dye stuffs. Various dyes, including Carmine, Congo Red, Methyl Red, Neutral Red, Methyl Green, Brilliant Green, Brilliant Cresyl Blue, Trypan Blue, Basic Fuchsin, Crystal Violet, Gentian Violet, Aniline Violet, Orange G, Eosin B, Bismark Brown, and Methylene Blue,∗ were added in relatively high concentrations to bacteriophage filtrates, which were then kept at incubator temperature, in part at room temperature, for 24 hours or longer and thereafter tested for lytic activity. No appreciable influence on any of the bacteriophages was noted, with the single exception of the effect produced on the 2 staphylococcus bacteriophages by methylene blue. These particular bacteriophages were completely inactivated within 6 to 12 hours by concentrations of the dye as low as 0.002%. Five serial passages on susceptible staphylococci failed to elicit any evidence of residual active principle. Believing that the action might be due to some impurities in the methylene blue, we then employed the dye after careful recrystallization. The same results were realized. Eight other bacteriophages, including races of anticoli, antidysentery, antityphoid, and antiproteus bacteriophages did not appear to be influenced in the least by the dye. The susceptibility to methylene blue appears therefore to be peculiar to the 2 races of staphylococcus bacteriophages examined for this property. This susceptibility may possibly extend itself to bacteriophages active for other non-intestinal bacteria as well as to other antistaphylococcus bacteriophages. The mechanism of the inactivation is not exactly clear, hut will be studied further. We have been able to satisfy ourselves that it is not in any way related to pH changes induced by the dye in the medium.