Comparison of Bacteriostatic Effects of Sulfanilamide and Sulfapyridine (2 Sulfanilyl Aminopyridine) on Bacteria in Broth Cultures. ∗

Abstract

Fleming 1 has recently reported that sulfapyridine—2(sulfanilyl aminopyridine)—in concentrations of from 1:256,000 to 1:8,000 inhibited the development of large inocula of type 23 pneumococci in deleucocyted human blood. In the presence of leucocytes a concentration of 1:32,000 sulfapyridine killed an inoculum of 100,000 pneumococci. The drug had a similar effect upon hemolytic streptococci. Bacteriostasis was obtained in the absence of leucocytes, while in their presence actual killing occurred. A comparison of the efficacy of sulfanilamide and sulfapyridine in whole blood showed that the latter was the more effective against hemolytic streptococci and type 15 pneumococci. Fleming used the slide cell technic which he described some years ago. We 2 have already shown that sulfapyridine is as effective a bacteriostatic agent as sulfanilamide against a strain of beta hemolytic streptococcus (C203), and is somewhat more effective against Types I, II and III pneumococci in broth cultures. The present investigation was undertaken with the purpose of comparing the action of sulfapyridine and sulfanilamide against a miscellaneous group of microörganisms.

One strain each of beta hemolytic streptococci, Groups B, C, and D, alpha, hemolytic streptococcus, Staphylococcus aureus, E. coli and E. typhi were tested for susceptibility to 10, 50, and 90 mg% concentrations of sulfanilamide and sulfapyridine in beef infusion broth (2% Neopeptone, 0.075% dextrose). A series of tubes, containing the desired concentrations of the 2 drugs in broth and a drug-free control, were inoculated with 0.5 cc of culture dilution. The cultures had been grown in broth at 37°C for 5 or 6 hours, and the dilutions, made with the same medium, were sufficiently high in most instances to give inocula of less than 100 organisms. The size of the inoculum and the extent of growth in the tests after 20 hours'incubation were determined by pouring plates and counting the colonies which developed.