The In vitro Effects of Penicillin on the Growth of Trichomonas foetus

Abstract

A great deal of work has been performed concerning the effects of antibiotics on bacteria, both in vitro and in vivo. In sharp contrast, very little investigation has been made of the possible effects of the various antibiotics on protozoa. The purpose of this research is to present data concerning the in vitro effects of penicillin on the population growth of Trichomonas foetus, a protozoan.' T. foetus, a parasitic flagellate, was chosen as a representative protozoan because of the relative ease with which it can be grown on artificial media as compared to most pathogenic protozoa, and because it was easily obtainable in pure culture. It is the cause of bovine trichomoniasis (trichomonas disease, trichomonad abortion, trich or early abortion) and is found in the reproductive organs of cattle suffering from the disease. T. foetus is characterized by three anterior flagella, an undulating membrane, and an axostyle which runs through the entire body and projects as a short tail. It is about 15 [ long by 6 [ wide. Antibiotics have been used by some workers as a means of obtaining bacteria-free cultures of protozoa. Mahmoud (1944) used 30 units of penicillin per tube of medium and obtained bacteria-free cultures of T. foetus. Williams and Plastridge (1946) tried various antibiotics; among them were penicillin, streptomycin, clavacin, gramicidin and actinomycin. They found that clavacin, gramicidin and actinomycin, when added to the basic medium' in concentrations sufficient to control bacteria, were toxic for T. foetus. They obtained better results with penicillin and streptomycin used in combination. Morgan and Campbell (1946), in testing 350 compounds for possible trichomonacidal effects, found that penicillin in a concentration of 8.0% (80,000 units per milliliter) killed T. foetus in one minute, and that tyrothricin in a concentration of 0.03% also killed T. foetus in one minute. Morgan (1946), in addition, used antibiotics in obtaining bacteria-free cultures of T. foetus. The present investigation is designed to ascertain whether or not penicillin, in concentrations lower than the massive doses used by Morgan and Campbell, inhibits the growth of T. foetus, and if so, to demonstrate the critical range by means of population growth curves. Comparisons will be made between different manufacturer's products to determine any differential effect that may arise.