ELECTRON MICROSCOPE STUDY OF BACILLUS ANTHRACIS IN MOUSE SPLEEN

Abstract

Mice were infected with virulent B. anthracis by means of an intraperitoneal injection of a saline suspension of vegetative organisms. The mice were sacrificed when moribund and the spleen was removed and cut into 1mm3 pieces under fixative (2% KMnO4 in distilled water). Tissue was fixed for two hours at room temperature, dehydrated and then embedded in Araldite Epoxy resin and ultrathin sections were cut and observed. Structures observed were similar to those described previously in in vitro studies of aerobic sporeformers. A cytoplasmic membrane was evident as were a well defined cell wall and nucleoid elements. The host spleen cell structures which were recognized included mitochondria, nuclei, nuclear and cytoplasmic membranes and endoplasmic reticulum. An area of clearing seen around each bacterial cell was designated as the cytopathic area. Bacterial cells in various stages of division and structures which suggest a prespore were seen. The fixation was such that both the host cell structure and the bacterial cell structure were well preserved.