Coinfection by Mycobacterium marinum and Mycolicibacterium fortuitum in a captive adult diamondback water snake causing disseminated mycobacteriosis with acute cutaneous ulceration

Abstract

An adult male captive diamondback water snake ( Nerodia rhombifer) was found dead after a 1-d history of lethargy and cutaneous ulcers. The snake had eaten 2 sunfish ( Mola spp.) 5 d before death. Gross examination revealed white-to-tan nodules in the lung and liver and segmental intestinal impactions with digested fish. Histopathology confirmed disseminated granulomas with numerous intrahistiocytic acid-fast bacteria in the skin, skeletal muscle, lung, liver, and intestines. Mycobacterium marinum and Mycolicibacterium fortuitum were identified by culture of the hepatic granuloma, followed by PCR and rpoB gene sequencing. To our knowledge, this is the first description of M. marinum and M. fortuitum coinfection in this species. Although M. fortuitum has been isolated from reptiles, lesions associated with its presence in tissues have not been described previously. Interestingly, the mineralization within granulomas that we observed in our case is not reported in mycobacterial infection in reptiles, whereas this finding is common in mammals.