Effects of trypan blue and related compounds on production and activity of streptolysin S

Most dyes related to trypan blue inhibited hemolytic activity of oligonucleotide-streptolysin S (SLS) complex, an exotoxin produced by Streptococcus pyogenes. Order of the inhibition was: trypan blue greater than benzo blue 2B greater than Congo red greater than Evans blue greater than benzo purpurine 4B greater than thiazine red greater than trypan red. When resting streptococcal cells were incubated with these dyes, significant amount of the hemolysin was produced. The carrier (or inducing) activity for SLS was further manifested in growing cell system and the potency of the compounds was as follows: Congo red greater than benzo blue 2B greater than trypan blue greater than Evans blue greater than Benzo purpurine 4B greater than or equal to thiazine red greater than trypan red. In this system, Congo red was more effective than oligonucleotide fraction rich in guanyl residue. Chromotrope 2B, H acid and o-tolidine were ineffective, as the carrier as well as the inhibitor. Based on these results, structure-function relationship among SLS, the carrier and the inhibitor was discussed.