Tetrazolium [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] reduction by mycoplasmas

We investigated 22 mycoplasma and acholeplasma species for their ability to reduce tetrazolium salts by using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. The test results were evaluated visually, as well as spectrophotometrically, by using an enzyme-linked immunosorbent assay reader. Our results were very similar to the results obtained when the tetrazolium salt reduction assay described by Aluotto et al. was used. However, the MTT reduction assay appeared to be better because it is faster, more objective and sensitive, easier to evaluate, and less expensive; in addition, it allows quantitative determinations. By using regression analysis a linear correlation between formazan production and the number of colony-forming units was demonstrated for all of the species investigated, indicating that the MTT assay can also be used for growth, toxicity, or chemosensitivity tests for the mycoplasma species that are capable of reducing tetrazolium salts.