Granulomatous pulmonary reactions after instillation of Mycobacterium gordonae. Light and electron microscopic investigations on the rat model.

Pathogenicity of Mycobacterium gordonae in humans has so far been reported in the literature in the form of case reports only. Systematic experimental investigations have not been published. For this reason, the pathogenicity of two Mycobacterium gordonae strains isolated from human ivestigation material were tested in animal experiments. Measured amounts of in some cases live and in some cases heat-killed M. gordonae were instilled into the right lower lobe of the lung of anesthetized Wistar rats by means of a polyvinyl catheter. The tissue changes were investigated at graduated time intervals between 1 h and 24 weeks by light and electron microscopy. Small granulomas consisting of leukocytes and macrophages develop in the lung tissue 3 days after the instillation. Under the electron microscope, intracellular mycobacteria can be demonstrated. These do not proliferate. After 2 weeks, sarcoid granulomas have formed from epitheloid and giant cells. Casefying necroses are absent. Electron microscopically, it can be shown that the mycobacteria are broken down intracellularly in phagolysosomes, so that sarcoid granulomas free of bacteria are left behind.