A Simple Culture Medium for Endamoeba Histolytica

Abstract

As contrasted with various media generally used in the cultivation of Endamoeba histolytica, the proposed medium is simple in its composition. It consists of sterile nutrient broth and a mixture of starch and charcoal. The nutrient broth is adjusted to pH 7.0 and is left in an incubator until used, or warmed to about body temperature at the time of inoculation of a suspected material. To the above medium is added rice starch and animal charcoal mixture (in the proportion of 2:1 by volume) briefly designated as S.C. mixture in this paper. A small amount of the S.C. mixture is loosely placed in a small tube and sterilized by dry heat at 180°C. for 45 minutes. Rice starch, according to Dobell and Laidlaw, 1 provides the amoebae with a definite source of assimilable carbohydrates and also inhibits the growth of Blastocystis frequently found in feces. Animal charcoal is used to adsorb ammonia and hydrogen sulphide present in the culture, thus reducing their deleterious effects upon the amoebae, while calcium phosphate contained therein helps to stimulate the metabolic activities of the organisms.

Formed stool is thoroughly mixed by means of a sterile glass rod in order to obtain a uniform distribution of the cysts. Liquid stool should first be sedimented, and the supernatant fluid decanted. Washed cysts are then prepared by filtration and sedimentation of the stool, followed by repeated washings with centrifuging. Cysts in freshly sedimented stools grow almost as well as those obtained in the stools left standing for several hours at room temperature or in a refrigerator.