Mycobacterium helveticum sp. nov., a novel slowly growing mycobacterial species associated with granulomatous lesions in adult swine.

The occurrence of nontuberculous mycobacteria in different hosts and their implication as obligate or opportunistic pathogens remain mainly unclear. Mycobacteriosis in pigs is usually associated with members of the Mycobacterium avium complex and, in particular, infections with “Mycobacterium avium subsp. hominissuis”. Here we describe a novel slow growing mycobacterial species isolated from lymph nodes obtained from two sows housed in different Swiss farms. The animals presented chronic inappetence and/or mild diarrhea. Gross pathology revealed focal granulomatous caseous lymphadenopathy of the mesenteric lymph nodes. Complete genome sequencing of two isolates from the two sows was performed. The genomes comprised 5,76 Mb and an average nucleotide identity score of 99.97%. Phylogenetic, mycolic acid and matrix-assisted laser desorption ionization-time of flight mass spectrometry analyses revealed that the two isolates were not related to any previously described Mycobacterium species. Based on complete genome investigations, the closest related species is M. parmense, a slow growing scotochromogenic Mycobacterium first isolated from a cervical lymph node of a 3-year-old child. The name proposed for the new species is Mycobacterium helveticum sp. nov. and 16-83T (=DSM 109965T= BCCM/LMG 2457T) is the type strain.