Identification of Mycobacterium Agent Isolated from Tissues of Nile tilapia (Oreochromis niloticus)

Nile tilapia culture in Campeche, Mexico experiences sporadic and significant fish mortalities, where mycobacteriosis signs of disease are detected. Thirty fishes(30 +/- 4 g) from different farms were monitored after a disease outbreak. Nile tilapia (Oreochromisniloticus) samples (60%) of spleen, liver and stomach display multiples granulomas with a thick capsule, walled off by epithelioid cells and robust acid-fast rods on the necrotic center. A great number of acid-fast bacilli where detected with Ziehl-Neelsen stain protocol. The bacteriological analysis of kidney displayed a 90% (26 organisms) of positive development in Lowenstein-Jensen medium with yellow or orange colonies when exposed to light and acid-fast rods. A 562-bp fragment confirms the positive result of the presence of the Mycobacterium spp.by PCR analysis,where phylogenetic analysis suggests that Mycobacteriumfortuitum and M. marinum were the principal mycobacterial species associated with tilapia mortality in Campeche, Mexico.