Abstract
Bovine tuberculosis (TB) caused by Mycobacterium bovis is a significant health threat to cattle and a zoonotic threat for humans in many developing countries. Rapid and accurate detection of M. bovis is fundamental for controlling the disease in animals and humans, and for the proper treatment of patients as one of the first-line anti-TB drug, pyrazinamide, is ineffective against M. bovis. Currently, there are no rapid, simplified and low-cost diagnostic methods that can be easily integrated for use in many developing countries. Here, we report the development of a loop-mediated isothermal amplification (LAMP) assay for specific identification of M. bovis by targeting the region of difference 4 (RD4), a 12.7 kb genomic region that is deleted solely in M. bovis. The assay's specificity was evaluated using 139 isolates comprising 65 M. bovis isolates, 40 M. tuberculosis isolates, seven M. tuberculosis complex reference strains, 22 non-tuberculous mycobacteria and five other bacteria. The established LAMP detected only M. bovis isolates as positive and no false positives were observed using the other mycobacteria and non-mycobacteria tested. Our LAMP assay detected as low as 10 copies of M. bovis genomic DNA within 40 minutes. The procedure of LAMP is simple with an incubation at a constant temperature. Results are observed with the naked eye by a color change, and there is no need for expensive equipment. The established LAMP can be used for the detection of M. bovis infections in cattle and humans in resource-limited areas.
Highlights
Mycobacterium tuberculosis, the archetypal member of the M. tuberculosis complex (MTC), is the principal causative agent of tuberculosis (TB) in humans [1]
Routine laboratory methods used to identify tuberculosis (TB) in high-burden countries do not distinguish between the two main causes of TB in humans, namely Mycobacterium tuberculosis and M. bovis
A loop-mediated isothermal amplification (LAMP) based method was developed to identify M. bovis. This LAMP method detected M. bovis within 40 minutes following incubation at constant temperature (66 ̊C) in a battery-powered incubator and results could be read with the naked eye following development of a color change
Summary
Mycobacterium tuberculosis, the archetypal member of the M. tuberculosis complex (MTC), is the principal causative agent of tuberculosis (TB) in humans [1]. Mycobacterium bovis, which is the main causative pathogen of bovine TB, causes TB disease in humans which is termed ’zoonotic TB’. In both hosts, M. bovis infections pose serious challenges. The losses incurred include condemnation of carcasses at slaughterhouses, mortalities and costs involved in the implementation of disease control measures [2,3] These challenges are immense mostly in developing and high burdened countries in comparison to developed countries. In the latter, appropriate food hygiene measures such as milk pasteurization and "test and slaughter" control programs to remove infected animals have helped reduce the disease burden. If M. bovis is detected during routine TB diagnosis, the standard TB regimen can be optimized [5]
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