Abstract
The contribution of Mycobacterium bovis to the proportion of tuberculosis cases in humans is unknown. A retrospective study was undertaken on archived Mycobacterium tuberculosis complex (MTBC) isolates from a reference laboratory in Uganda to identify the prevalence of human M. bovis infection. A total of 5676 isolates maintained in this repository were queried and 136 isolates were identified as pyrazinamide resistant, a hallmark phenotype of M. bovis. Of these, 1.5% (n = 2) isolates were confirmed as M. bovis by using regions of difference PCR analysis. The overall size of whole genome sequences (WGSs) of these two M. bovis isolates were ~4.272 Mb (M. bovis Bz_31150 isolated from a captive chimpanzee) and 4.17 Mb (M. bovis B2_7505 from a human patient), respectively. Alignment of these genomes against 15 MTBC genome sequences revealed 7248 single nucleotide polumorphisms (SNPs). Theses SNPs were used for phylogenetic analysis that indicated a strong relationship between M. bovis and the chimpanzee isolate (Bz_31150) while the other M. bovis genome from the human patient (B2_7505) analyzed did not cluster with any M. bovis or M. tuberculosis strains. WGS analysis also revealed multidrug resistance genotypes; these genomes revealed pncA mutations at positions H57D in Bz_31150 and B2_7505. Phenotypically, B2_7505 was an extensively drug-resistant strain and this was confirmed by the presence of mutations in the major resistance-associated proteins for all anti-tuberculosis (TB) drugs, including isoniazid (KatG (S315T) and InhA (S94A)), fluoroquinolones (S95T), streptomycin (rrs (R309C)), and rifampin (D435Y, a rare but disputed mutation in rpoB). The presence of these mutations exclusively in the human M. bovis isolate suggested that these occurred after transmission from cattle. Genome analysis in this study identified M. bovis in humans and great apes, suggesting possible transmission from domesticated ruminants in the area due to a dynamic and changing interface, which has created opportunity for exposure and transmission.
Highlights
Mycobacterium bovis, a subspecies of the Mycobacterium tuberculosis complex (MTC), is a significant cause of bovine tuberculosis in the developing world [1,2]
Permission to use isolates for molecular characterization was obtained from the research committee of the Joint Clinical Research Centre (JCRC); the JCRC Uganda-Case Western Reserve University (CWRU) Research Collaboration and Microorganisms 2019, 7, 221 the Molecular Diagnostics Laboratory Department of Medical Microbiology, College of Health Sciences (CHS), Makerere University Kampala
We carried out comparative genomics on archived pyrazinamide resistant MTC isolates from a multicenter study archive in Uganda to determine if there was a non-random distribution of genomotypes of MTC organisms infecting humans and animals in Uganda with the use of genome-wide single nucleotide polymorphisms (SNPs) to differentiate MTC organisms
Summary
Mycobacterium bovis, a subspecies of the Mycobacterium tuberculosis complex (MTC), is a significant cause of bovine tuberculosis (bTB) in the developing world [1,2]. Bovine TB (bTB) has nearly been eradicated from domesticated animals, the risk of human transmission is low. This was achieved through mandatory testing of cattle, removal of positive reactors and in-contact animals, and compulsory pasteurization of milk [5,6,7]. In resource-limited countries where the devastation of MTCs on humanity continues unabated, effective disease-control measures, like mandatory milk pasteurization and removal of positive reactors, is difficult to implement mainly due to economic factors [8,9,10,11,12]. BTB is not reportable in many countries in sub-Saharan Africa and there are no compensatory mechanisms in place for farmers whose animals test positive for the disease [6,13,14,15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
