Mycobacterium marinum M

Mycobacterium marinum, a ubiquitous pathogen of fish and amphibia, is a near relative of Mycobacterium tuberculosis, the etiologic agent of tuberculosis in humans. It is Gram-positive, rod-shaped, facultative anaerobic bacterium commonly found in various aquatic environments around the world, including swimming pools and drinking water. In 1926, Joseph D. Aronson isolated a Mycobacterium from tubercles observed predominantly in the spleen and liver of diseased fish that had died in the Philadelphia Aquarium and named it M. marinum. It was subsequently shown to also be a human pathogen when it was isolated again much later in a swimming pool-associated outbreak of human granulomatous skin lesions, although in this report the Mycobacterium was mistakenly given a new species name, Mycobacterium balnei, a name that is no longer used. This bacterium causes a tuberculosis-like disease in frogs, fish and other poikilothermic animals, and a peripheral granulomatous disease in humans. M. marinum infection of humans, called fish tank or aquarium tank granuloma, typically occurs when M. marinum is inoculated through the skin by cuts and scratches following direct contact with an infected fish or contaminated aquatic environments. The ensuing granulomatous infection generally limited to the skin and soft tissues extremities is pathologically indistinguishable from M. tuberculosis dermal disease. Its optimal growth temperature is 35 degrees Celsius (in Middlebrook 7H9 medium). Its lower optimal growth temperature likely explains its causing systemic disease in poikilotherms animals and a superficial disease, restricted cooler extremities of the body, in warm-blooded animals. In contrast to M. tuberculosis, it is unable to reduce nitrate and produces characteristic bright yellow carotenoid pigments when exposed to light. These photochromogenic pigments protect it from UV damage in incident sunlight by reducing singlet oxygen species. It can form biofilms. (EBI Integr8)