Abstract

Aim
This study investigated the presence and extent of Mycobacterium bovis infection among human tuberculosis (TB) patients attending Murtala Memorial Hospital, Sokoto, Nigeria, a region with a high risk of zoonotic TB and limited prior molecular data.
Methods
Ninety-eight TB patients were screened between December 2016 and June 2017. Of the 63 smear-positive sputum samples cultured on Lowenstein-Jensen medium, 25 yielded mycobacterial growth. DNA extracted from these cultures was subjected to PCR amplification of the hsp65 gene. Amplification was obtained in nine isolates, six of which yielded high-quality sequences for BLAST analysis. Isolates identified as members of the Mycobacterium tuberculosis complex were further analyzed using a 470 bp M. bovis-specific PCR assay. Phylogenetic and pairwise genetic-distance analyses were performed.
Results
BLAST analysis identified one isolate as Mycobacterium columbiense, while five belonged to the M. tuberculosis complex. The M. bovis-specific fragment was detected in four of these five isolates (4.1% of all patients). Phylogenetic analysis confirmed clustering within the M. tuberculosis complex. Pairwise genetic-distance analysis showed no divergence between M. tuberculosis and M. bovis based on hsp65, but revealed 13.2% divergence between M. canettii and M. novocastrense, and 16.4% divergence between M. tuberculosis complex members and non-tuberculous mycobacteria.
Conclusions
This study confirms the occurrence of zoonotic tuberculosis among the tuberculous patients tested. The detection of Mycobacterium bovis in human sputum, together with previous reports of M. tuberculosis in local livestock, underscores the need for strengthened One Health surveillance to better understand animal-human transmission dynamics.
Keywords: Genotyping; Mycobacterium bovis; Tuberculosis; Sokoto; Zoonosis

Key words: Molecular identification, Mycobacterium bovis, Tuberculosis, Sokoto, Zoonosis