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An Accurate Method for the Numerical Determination of Endamoeba Histolytica in Vitro and its Possible Use with Other Intestinal Protozoa; Suggested Clinical Application¹

By the use of a haemocytometer Endamoeba histolytica can now be studied quantitatively in culture under varying conditions, making it possible to analyze and evaluate culture methods. In our hands, this method has proved to be accurate and practical.

The technique is simple: the contents of the culture save, obviously, for the solid horizontal or slanting base, is gently but thoroughly mixed, preferably with a capillary pipette, so as to insure uniform distribution of the protozoa and a drop is placed therefrom in the haemocytometer. The organisms are counted and totals determined as are cells in spinal fluid: the result equals the number of organisms per cubic millimeter of culture.

As a result of more limited observations, it has been found to apply equally well to Endolimax nana and, with slight modification, to Trichomonas hominis. These studies indicate that this method might be employed similarly in quantitative cultural observations of other amoebae, ciliates and flagellates.

It is further indicated that differential tabulation of cysts and trophozoites, as well as of several species of protozoa living together in material to be examined, is possible. This may be accomplished by the addition of an equal quantity of iodine solution to a specific amount of material to be examined, the total then being multiplied by two to account for dilution, to secure the number of varieties of organisms per cubic millimeter of material.

This method of numerical determination of Endamoeba histolytica was modified so as to be applied clinically in a human case of acute intestinal amoebiasis, and in an Endolimax nana infection in a patient with idiopathic ulcerative colitis. The numerical extent of amoebal involvement before and in association with therapy was determined by securing rather definite quantities of material directly from the rectum and sigmoid through a rectosigmoidoscope, and from freshly defecated feces. A drop of this material in suspension was placed under the cover slip in a haemocytometer and the procedure in counting was the same as for numerical determinations of organisms per cubic millimeter of culture. This phase of the study was sufficient to suggest the clinical value of such a method; however, further investigation along these lines is desirable.

¹ From the Departments of Medicine, Gastro-Intestinal Clinic, and Pathology and Bacteriology of the Johns Hopkins Hospital and University School of Medicine, Baltimore, Maryland.

² Instructor in Medicine and Assistant Visiting Physician, Johns Hopkins University and Hospital, respectively.