Resistance In Vitro of Leishmania Donovani to Contamination with Bacteria

Abstract

Leishmania donovani, the causative agent of Kala-azar, is generally believed to be a delicate organism which cannot survive in the presence of common bacteria. The studies of Spagnolio 1 and those of Giugni and Benoni 2 tended to indicate that contamination with various common bacteria is detrimental to the culture of this parasite. The recent demonstration by Forkner and Zia 3 , 4 and those of Giugni and Benoni 2 tended to indicate that contamination with various common bacteria is detrimental to the culture of this parasite. The recent demonstration by Forkner and Zia 3 , 4 of viable and infective Leishmania donovani in the midst of numerous bacteria in the oral and nasal secretions of 13 out of 14 patients suffering from Kala-azar has, however, led us to alter our concept concerning the resistance of this parasite to bacterial contamination and prompted us to test more specifically the exact relationship which exists in vitro between Leishmania donovani and some of the common bacteria with which they may be associated in the mammalian host.

The well-known and commonly employed N.N.N. (Novy-Mac Neal-Nicolle) medium is obviously unsuitable for our experiment, since the parasite will not grow or multiply in this medium in the presence of bacterial contamination. We found that a simple medium, with which Carter 5 successfully cultured Leishmania tropica from contaminated oriental sores, was suitable for our purpose. The medium used by us was prepared with slight modification and simplification, as will be reported in our final publication.

The Leishmania donovani used in the experiments were obtained from 2 sources. The flagellates were obtained from a 2 or 3 weeks old culture on N.N.N. medium. Leishman-Donovan bodies were obtained from the spleens of infected Chinese hamsters. The animals were killed with ether anesthesia and the spleens removed with aseptic technique. Emulsions were made by macerating approximately one-third or one-fourth of each of the spleens in 3 or 4 cc. of sterile 0.9% sodium chloride solution, and they were then ready for use.