Mycobacterium marinum

The first report of a mycobacterium isolated in fish, supposed to be Mycobacterium marinum, has been attributed to Bataillon et al. (1897), who isolated acid-fast bacilli named Mycobacterium piscium from a tuberculous lesion in a common carp (Cyprinus carpio) (1). M. marinum was then originally isolated and identified from marine fish at the Philadelphia Aquarium (2). M. marinum was initially thought to infect marine fishes only and was named accordingly, but it is now known to be a ubiquitous species. The above-mentioned original freshwater isolate of M. piscium could be a M. marinum variant. In the early literature, several other marine Mycobacterium species were described, such as M. platypoecilus, M. anabanti, and M. balnei. Comparative sugar fermentative reactions together with published morphological, cultural, and pathogenic data suggested that they were all synonymous with M. marinum (3) even if M. piscium has not been recognized as a species since its type culture is no longer available.