Abstract
If 1 cc. of saturated aqueous solution of neutral red (5.6%) be put into tubes containing 1/2 cc. of heavy aqueous suspension of 24 hour culture of Staphylococcus aureus, B. prodigiosus, and B. anthracis, and plants be made on agar at the end of 48 hours, the organisms will grow as vigorously as if no dye had been present in the tubes. B. prodigiosus will be still capable of vigorous growth on transplant after 9 days' exposure to the saturated solution of the dye.
If, instead of saturated solution, 2% solution be used, all 3 organisms will grow vigorously on transplant even after 21 days' exposure, and B. prodigiosus and B. anthracis will grow well at the end of 35 days' exposure.
Staphylococcus aureus (now known to be highly susceptible to triphenyl methane dyes, like crystal violet) readily survives 24 hours' exposure to saturated aqueous solution of Bismarck Brown (1.2%); and B. anthracis (another organism susceptible to triphenyl methanes) put 39 days ago into this solution still grows vigorously when transplanted.
These observations again make clear that the statement sometimes made that a strong aqueous solution of dye stuff is eo ipso sterile must undergo considerable modification before it conforms with the facts.
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