Development of a LAMP assay for rapid and sensitive detection and differentiation of Mycobacterium avium subsp. avium and subsp. hominissuis.

Mycobacterium avium causes atypical mycobacterial infection in humans and animals worldwide. M. avium comprises the subspecies avium (MAA), hominissuis (MAH), silvaticum (MAS) and paratuberculosis (MAP). The M. avium complex (MAC), comprising M. avium and M. intracellulare, causes opportunistic infections of humans. M. avium subsp. avium (MAA) mainly causes avian tuberculosis while subsp. hominissuis (MAH) mainly infects pig. Distinguishing between these two subspecies is essential to the effective control of these atypical mycobacterial infections and minimization of the resulting economic loss. For this purpose, we developed a loop-mediated isothermal amplification (LAMP) assay that rapidly and sensitively detects and differentiates MAA and MAH. This MAA-LAMP assay targeting IS901 correctly detected four MAA isolates but did not detect 27 MAH and 19 non-MAA/non-MAH mycobacterial isolates. The MAAH-LAMP assay targeting IS1245 detected four MAA and 27 MAH isolates but not the other 19 mycobacterial isolates. We believe that implementation of this LAMP assay will significantly improve public health and safety. SIGNIFICANCE AND IMPACT OF THE STUDY: Mycobacterium avium, which is pathogenic for humans and animals, represents a continuing threat to public health and safety and to food production. Therefore, improved methods are urgently required to readily and efficiently identify M. avium subspecies. Compared with conventional PCR methods, the LAMP assay herein developed more rapidly detects and better distinguishes between two major M. avium subspecies that cause disease of pig. Importantly, this highly accurate and sensitive LAMP assay detects mycobacterial DNAs using real-time fluorescence or the unaided eye with a colour-change dye, making it ideal for translation to the clinic and slaughterhouse.