Charcoal Medium for Growth and Maintenance of Large and Small Races of Entamoeba Histolytica

Abstract

Culturing of the small race of Entamoeba histolytica has been difficult, and yet this phase of study has received little attention from investigators. Although Drbohlav reported growing a small race in 1925, it was not until 1936 that Spector reported growth of only 5 to 8 per cent of organisms of the small race from stools. Later, Meleney and Frye isolated the D strain. Perhaps the most concentrated efforts to culture the small race from stools were those of Sapero and co-workers, who reported uniform failure in more than 100 attempts. However, Spector and Sapero and his associates had no difficulty in culturing the large race with the technics that they used for the small race. In 1948, Reardon succeeded in isolating strain 110, and more recently, Shaffer and Schneider isolated the Conrad strain, but they failed to isolate additional strains from other stools in nearly 50 attempts. Norman and Brooke • mentioned culturing, but not isolating, the small race from stools. The lack of a satisfactory medium for isolating the small race led us to investigate the possibilities of a new medium containing charcoal. Tsuchiya added charcoal to the nutrient broth overlay of Dorsett egg medium in order to culture amebas, and Anderson and Hansen used charcoal as a substitute for starch. Hirsch provided us with a charcoal medium that was prepared for the culturing of Mycobacterium tuberculosis. The purpose of this paper is to describe 2 modifications of this medium that were developed for the maintenance of several well-established strains of the large race of E. histolytica, and for the isolation and maintenance of strains of the small race from stool specimens.