The use of tetrazolium salts in bioautographic procedures.

! WALLNAUSSER~ has pointed out that TTC (2,3,5-triphenyl-2H-tetrazolium chloride) as well as other redox indicators such as z,6-dichlorophenol-indophenol can be, successfully employed either as visualizing sprays or as additions to the assay media. Although the use of tetrazolium salts in bioautography is not novel, our experience leads us to believe that their use as visualizing systems in bioautographic procedures could be profitably increased. Recently, we developed a bioautographic procedure which, clue to the microorganism used for detection, gave indistinct zones of inhibition. This difficulty, plus the much greater variety of tetrazolium salts now commercially available, precipitated a study on our part to ascertain if use of one or more of these reagents would resolve our problem.