Observations on the Response in Vitro of the Pneumococcus, Staphylococcus, Alpha Hemolytic Streptococcus, and Friedlander's Bacillus to the Sulfonamide Drugs *

Review of the reported work in this field discloses results which are in part contradictory, possibly due to the employment of various methods and to differences in media used. The data on each organism with which this paper deals are presented separately. Pneumococci.-Lawrence,6 using a peptone broth, found that sulfathiazole and its derivatives (phenyland methyl-) exerted a much greater bacteriostatic effect on Types I, II, and III pneumococci than did either sulfapyridine or sulfanilamide. The action of the drugs was purely bacteriostatic rather than bactericidal, probably due to the large number of organisms in the original inoculum. Lowell, Strauss, and Finland9 tested 45 strains recently isolated from patients and found that half of them showed a "slightly greater susceptibility" to sulfathiazole than to sulfapyridine. Only one strain was inhibited more by sulfapyridine than by sulfathiazole. The action of the drugs was determined by noting the highest concentration at which visible growth was present at 48 hours, and also by observing the lowest concentration of drug at which cultures, after incubation for 72 hours, yielded sterile subcultures on the surface of blood-agar plates. A considerable variation in response of different strains to the same drug was evident, as has been shown