Some Factors Related to Entamoeba Histolytica Growth on Rice Products in a Simple Medium

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  • Department of Microbiology, Medical College of Virginia, Richmond, Virginia
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These studies have led to the cultivation of Entamoeba histolytica in a simple medium limited in nutrient to rice flour. The inclusion of other nutrients in media used heretofore has hindered adequate observation of the growth-supporting capabilities of this substance.

The medium, magnesium phosphate agar-phosphate buffered saline, is composed of an agar slant containing two per cent dibasic magnesium phosphate overlaid with phosphate buffered saline (pH 7.4). If sterile rice flour is added as food, E. histolytica accompanied by a mixed bacterial flora can be cultivated indefinitely by serial transfer at four to six day intervals.

The medium was applied to study of nutrients in a series of tests to observe the growth response of E. histolytica to a number of rice products. It was observed that rice bran will not support growth. Rice polish obtains survival for only a few transfers possibly because of intensified bacterial growth. Rice flour, ground from either unpolished or polished rice, will support growth and multiplication with serial transfer indefinitely. Pure rice starch will not support growth and survival is limited to a few transfers. The deficiency of this product may be due to the elimination of the intergranular protein matrix associated with the starch granules in the rice kernel.

Magnesium phosphate agar-phosphate buffered saline medium appears to meet the need for a simple easily prepared medium for use in E. histolytica growth studies. It should afford added opportunity for study of the role of the bacterial flora and other factors requiring elucidation in order to establish E. histolytica in pure culture.