Typhoid Leukocidin

Abstract

Typhoid leukocidin may readily be demonstrated in the filtrate of a 24-hour culture of Eberthella typhosa grown in plain sodium chloride veal infusion broth, pH 7.4–7.6, without addition of peptone. Typhoid leukocidin passes readily through Berkefeld N, Chamberland L3, and Seitz EK filters. The leukocidin may be adsorbed by the filter unless suitable precaution is taken.

The demonstration of leukocidal activity may be accomplished by the Neisser-Wechsberg 1 method as used by Gay and Oram, 2 but we have used a method of direct determination which is simple in principle and has yielded more satisfactory quantitative and qualitative data than the older method. For this purpose we have utilized normal rabbit's blood and non-immune human blood. The blood is collected directly into heparin, mixed, and distributed to tubes before there has been any opportunity for the leukocytes to settle out. Equal volumes of varying dilutions of the toxic filtrate are quickly added to the tubes of blood; appropriate control tubes of blood plus plain broth are always included. The tubes are sealed with paraffined corks and incubated at 37°C. in a rotating box for one hour. Following incubation, the tubes are transferred immediately to a mechanical blood-pipette shaking device and agitation is maintained until total white cell counts and films for differential counts can be obtained. It is necessary to have as many pipettes and counting chambers as there are tubes, to insure a minimal difference of time between the taking of the different counts. Tubes for counting are selected at random rather than in the order of dilution of the filtrate. Counts of control tubes are essential. After the differential counts have been completed, the total number of leukocytes of each type is calculated and the data plotted in order of dilution of the filtrate.