Effect of Sulfapyridine (Dagenan) on Brucella abortus in vitro and in vivo. ∗

Abstract

In vitro. A virulent, aerobic strain of Brucella abortus was used in this experiment. Tryptose broth and Tryptose agar respectively were used for the in vitro experiment. Sulfapyridine was added to 100 cc of broth in flasks to give each of the following dilutions: 1:1,000; 1:10,000; and 1:100,000. Each dilution was made in triplicate. Three flasks of broth without sulfapyridine were left as controls. Sulfapyridine was added to the broth before autoclaving to obtain complete solution of the drug. All flasks of broth were inoculated with the same amount of dilute bacterial suspension. Petri plate counts made on each flask of broth at the beginning of the experiment averaged between 5,000 and 6,000 organisms per cubic centimeter. The inoculated broth was incubated at 37.5°C and Petri plate counts made in duplicate 10 minutes, 1, 2, 3, 5, and 7 days after addition of the organisms. The bacterial content of the inoculated broth after the various intervals of incubation was determined on dilutions of 1:100, 1:10,000 and 1:1,000,000 by placing 1 cc of each dilution in Petri plates in duplicate and adding 25 cc of Tryptose agar. The plates were incubated at 37.5°C for 96 hours and the number of colonies counted. Final counts were based on the averages of the three samples in each dilution group. The results of the final counts are shown in Table I.

The results of this experiment show that sulfapyridine has a definite bacteriostatic action on Brucella abortus in vitro. The decrease in the number of oganisms is especially noticeable after 5 days in the 1:1,000 and 1:10,000 concentrations of sulfapyridine. After 7 days, there is no appreciable difference in the number of organisms in the 2 dilutions.