Abstract
Summary
Effects of various concentrations of tyrocidine, an antibiotic substance produced by Bacillus brevis, have been tested on in vitro cultures of Trypanosoma cruzi. Concentrations of 100 γ tyrocidine/cc and over show a growth-depressing effect on T. cruzi cultures even in the presence of serum, such an effect being increased proportionately with antibiotic concentration, until with 200 γ/cc and a few hours' exposure, the lethal dosage is reached. The effects of tyrocidine in vitro on T. cruzi are only slightly influenced by temperature over a range of 20°C to 30°C. When the pH of the culture medium reaches 6.0 or lower, morphological changes in the flagellates are produced. Vacuolation and rounding up occur in both control and antibiotic-containing cultures and do not seem to be due to the influence of tyrocidine. but rather to a change in the hydrogen-ion concentration of the culture medium, with possibly the actions of metabolites in an ageing culture.
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