Mycoplasma-like organism induced murine cardiac microvasculopathy. A transmission electron microscopic study.

Mycoplasma-Like Organisms [MLO] are intracellular cell wall deficient bacteria that cause ocular chronic vasculitis in man and chronic vascular disease in plants. Since MLO do not grow in culture, diagnosis of MLO-induced disease requires identification of the organisms by electron microscopy. Ultrastructurally, MLO appear as pleomorphic tubulo-spherical and filamentous organisms. In human ocular disease MLO have been detected in parasitised leucocytes and retinal pigment epithelial cells. We have previously reported the results of injecting MLO infected human vitreous into mouse eyelids. Two thirds of the mice developed chronic disease at the inoculation site, but, more importantly, the mice also developed lethal systemic MLO disease. Carditis with histologic features similar to those of various types of human carditis occurred in 18% of the mice. This report describes the ultrastructural features of the cardiac microvascular MLO disease in those 18 mice that died of carditis after inoculation with human MLO-infected vitreous. MLO were identified in leucocytes and endothelial cells of the murine vascular lesions. The vascular lesions were characterized by destruction of vessel walls as well as proliferation of endothelial cells. Electron dense deposits were seen in basement membranes and pericytial tissues. Similar features have been described in other bacterial vascular infections and in human idiopathic carditis. We suggest that MLO could be a cause of human cardiovascular disease and should be looked for in such cases.