A Study of Experimental Meningococcal Infection. II. Course of Infection

Abstract

Mice infected intraperitoneally by the method described in the preceding communication 1 rapidly sicken and die within a period of 12 to 48 hours, depending on the number of meningococci injected.

The cellular and microbic contents of the peritoneal cavities of the mice in several series were studied at intervals of about 2 hours. A drop of exudate was aspirated by means of a fine hypodermic needle inserted into the peritoneal cavity and examined microscopically in stained film preparation. As a check on this method the entire peritoneal exudate was withdrawn from mice sacrificed at corresponding times during the course of their infection and mixed and examined by means of cultures and smears. The results of these observations may be summarized as follows: Cells did not appear in the peritoneal exudate in any considerable number until about 4 hours after inoculation, even when very heavy suspensions of organisms had been injected. From that time on the number of cells increased rapidly. Approximately two-thirds of them were polymorphonuclear leucocytes and one-third large and small cells with a single nucleus and various amounts of cytoplasm. No special methods were employed to differentiate these cells. As the infection progressed an increasing fraction of the cells showed evidences of degeneration.

Following inoculation with small or moderately large numbers of meningococci evidence of multiplication was seldom obtained for several hours. After 4 to 6 hours, however, the number of organisms increased rapidly and apparently steadily until death occurred. When the infection was initiated by injection of relatively massive inocula the multiplication seemed to begin earlier. Irrespective of the number of organisms inoculated very few were seen within leucocytes at any stage of the infection when the strain employed was a highly virulent one.