Identification of Potentially Novel Mycobacterium Spp. In Freshwater Ornamental Fish in Trinidad and Tobago

Potentially zoonotic Mycobacterium spp. are impacting freshwater ornamental fish in Trinidad and Tobago. Clinical cases presented at the Aquatic Animal Health Unit of The University of the West Indies, School of Veterinary Medicine, from September 2011 to September 2018 indicated the presence of piscine mycobacteriosis in freshwater ornamental fish from locations throughout Trinidad and Tobago. Subsequently, an investigation was conducted from June 2018 to December 2021 to identify the specific Mycobacterium spp. involved. Nested polymerase chain reaction (PCR) was used to amplify and later sequence the 723 bp of the rpoB. Analysis of region V of the rpoB offers similar discriminatory power as concatenation or whole genome analysis of Mycobacterium spp., and serves as an acceptable method for differentiating and discriminating between species in this genus. With respect to tank-reared freshwater ornamental fish, this study identified M. fortuitum (98.8% identity), M. liflandii (100% identity), M. stomatepiae (97.2% identity), M. pseudoshottsii related (96.9% identity), two M. stomatepiae related (95.4% and 96.7% identity), M. immunogenum related (93.4% identity), and 17 M. insubricum related (91.4%-95.2% identity). Additionally, seven mycobacteria related to M. insubricum were identified in wild-caught guppies. These findings suggest that both known, and potentially novel Mycobacterium spp. are circulating, and adversely impacting the local populations of freshwater ornamental fish in Trinidad and Tobago.