Mycobacterium polyniensis sp.nov, a non-tuberculous mycobacterium clinical isolate from Tahiti, French Polynesia

In this study, we investigated a previously unidentified respiratory tract isolate, CSUR_Q5927, collected in Tahiti, French Polynesia. Through a comprehensive polyphasic approach combining phenotypic traits with whole genome sequencing, we sought to elucidate the identity and characteristics of this isolate. After cultivating colonies in Middlebrook 7H10 at 37 °C for nine days, we observed acid-fast bacilli under microscopic examination and Ziehl-Neelsen staining. Additionally, electron microscopy revealed the presence of unsporulated bacilli, approximately 1.27 μm +/- 0.26 μm in size, displaying morphology consistent with that of a mycobacterium. Matrix-assisted laser desorption/ionization mass spectrometry provided an identification score of 1.42, indicating a low confidence level. However, clustering analysis grouped isolate CSUR_Q5927 within the Mycobacterium terrae complex. Whole genome sequencing unveiled a CG-content of 68.5% and a coding ratio of 93.6%, comprising 4337 genes encoding proteins, 55 tRNA genes, and two rRNA. Further comparison with reference strain Mycobacterium terrae NCTC 10856 using DNA-DNA hybridisation values revealed a similarity of 35.8%, confirming the presence of a new species within the M. terrae complex. In vitro susceptibility testing demonstrated the isolate's susceptibility to eight antimicrobials and resistance to five others. After meticulously conducting appropriate negative controls and analysing all the data, we propose the name Mycobacterium polyniensis for this novel M. terrae species, with isolate CSUR_Q5927 serving as the prototype strain. This discovery expands our understanding of the microbial diversity in the Polynesian region and highlights the importance of combining advanced techniques to accurately characterise and classify previously unknown mycobacteria species.