The Action of Bacitracin and Subtilin on Treponema pallidum in Vitro and in Vivo

Abstract

Bacitracin was definitely treponemicidal for both the cultivated Reiter strain in vitro and pathogenic T. pallidum in vivo. Approx. 0.004 U./ml. completely inhibited growth of the former, and 0.025 U./ml. were treponemicidal within 24-48 hrs. The rate of the treponemicidal action increased with the conc. of bacitracin up to the largest concs. studied. In syphilitic rabbits, 36 U./kg. caused rapid disappearance of organisms from the primary lesion, but 5,000 U./kg. were necessary to effect permanent healing of the lesion if given as a single injn. In animals treated during the incubation period of the disease, 90 U./kg. given once daily for 4 days sufficed to abort the infection. In these separate methods of assay, crude prepns. of bacitracin assaying at 30 U./mg. were 10% as active as crystalline penicillin G. Subtilin was far less active than either penicillin or bacitracin against treponemata, whether the cultivated Reiter strain in vitro or the pathogenic organisms in vivo. In vitro, it was only 1% as active as penicillin G; and the largest doses so far used, approx. 80 X the curative dose of penicillin similarly injd., failed to cause even the permanent disappearance of treponemata from primary lesions in rabbits.