Characterization of Mycobacterium orygis as M. tuberculosis Complex Subspecies

Jakko van Ingen

, Zeaur Rahim, Arnout Mulder, Martin J. Boeree, Roxane Simeone, Roland Brosch, and Dick van Soolingen

Author affiliations: Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands (J. van Ingen, M.J. Boeree, D. van Soolingen); International Center for Diarrheal Disease Research, Bangladesh, Dhaka, Bangladesh (Z. Rahim); National Institute for Public Health and the Environment, Bilthoven, the Netherlands (A. Mulder, D. van Soolingen); Institut Pasteur, Paris, France (R. Simeone, R. Brosch)

Abstract

The oryx bacilli are Mycobacterium tuberculosis complex organisms for which phylogenetic position and host range are unsettled. We characterized 22 isolates by molecular methods and propose elevation to subspecies status as M. orygis. M. orygis is a causative agent of tuberculosis in animals and humans from Africa and South Asia.

Traditionally, the Mycobacterium tuberculosis complex comprises tubercle bacilli of 8 distinct subgroups: M. tuberculosis, M. africanum, M. canettii, M. bovis, M. caprae, M. pinnipedii, M. microti, and M. mungi (1–4). Two other distinct branches of the M. tuberculosis complex phylogenetic tree exist, the dassie and oryx bacilli, causative agents of tuberculosis in the animal species after which they are named. Neither has been validly described as separate taxa, nor have they been associated with disease in humans (1–4).
Oryx bacilli have been isolated from members of the Bovidae family, i.e., oryxes, gazelles (3), deer, antelope, and waterbucks (5), although their exact host range remains unsettled. No human disease caused by the oryx bacilli has been reported. These bacilli most likely constitute a separate phylogenetic lineage; however, their exact position has not been established with valid phylogenetic markers, such as large genomic deletions or single nucleotide polymorphisms (SNPs). To settle the phylogenetic position and host range of the oryx bacilli, we collected all oryx bacillus isolates from our laboratory database to establish their sources and subjected the isolates to extended phylogenetic analysis.