Culture of the organism that causes rhinosporidiosis.

The causative agent of rhinosporidiosis is a microscopic round body in polypoidal masses that is believed to be the sporangium of a fungus Rhinosporidium seeberi. But fungal aetiology can not be proved with certainty. Attempts to culture the fungus on various media have also been unsuccessful. In a recent study pond water samples, from water in which patients had been bathing, were analysed and a unicellular prokaryotic cyanobacterium Microcystis aeruginosa was isolated. The same cyanobacterium was demonstrated in clinical samples from patients with rhinosporidiosis. Consequent to these findings, attempts were made to culture the causative organism of rhinosporidiosis under conditions that support growth of cyanobacteria. This study describes a simple method for laboratory culture of this organism. Observations based on laser-scanning confocal microscopy, light and electron microscopy confirm that a cyanobacterium, Microcystis sp. is the causative agent of the disease. Rhinosporidiosis is the first human disease to be shown to be caused by a cyanobacterium. The findings have opened the way for development of therapy.