COMPARATIVE ACTIVITY OF SULFONAMIDES AGAINST KLEBSIELLA PNEUMONIAE (FRIEDLANDER'S BACILLUS)

¹ From the Institute for Medical Research, Christ Hospital, Cincinnati, Ohio

A study has been made of the relative effectiveness of sulfapyrazine, sulfadiazine, sulfapyridine, sulfathiazole and sulfanilamide against experimental infections with four different strains of Friedlander's bacillus and against these strains in vitro. Both when equal doses of the different drugs were administered and when similar concentrations were maintained in the blood, sulfapyrazine and sulfadiazine were much more active than sulfapyridine and sulfathiazole which in turn were somewhat more active than sulfanilamide. Sulfapyrazine and sulfadiazine were approximately equal in activity.

Infections with the different strains varied in their responsiveness to sulfonamide therapy but the order of activity of the various drugs was the same with all strains.

The order of activity of the different drugs in vitro was influenced by the composition of the test medium. In beef heart broth, sulfathiazole was the most effective drug; sulfapyrazine, sulfadiazine and sulfapyridine were approximately equal in activity, and sulfanilamide was the least active of the five drugs. In the synthetic medium, however, sulfathiazole, sulfadiazine and sulfapyrazine were approximately equal in activity; sulfapyridine was less active and sulfanilamide was again the least active derivative. Possible explanations for these differences in order of activity are discussed.

The orders of activity of the various derivatives against Friedlander's bacillus in vitro showed no correlation with the order of activity in vivo except that sulfanilamide was the least active drug in both cases. The significance of these observations has been discussed.

The various strains of Friedlander's bacillus differed in in vitro sensitivity to the sulfonamides. The orders of sensitivity of the strains were different in the two kinds of media except for strain S, which was the most sensitive strain in both media used.