Identification of Genes Encoded Toxin-Antitoxin System in Mycobacterium Tuberculosis Strains from Clinical Sample

The toxin-antitoxin system is a genetic element that is highly present in Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis. The toxin-antitoxin system comprises toxin protein and antitoxin protein or non-encoded RNA interacting with each other and inhibiting toxin activity. M. Tuberculosis has more classes of TA loci than non-tubercle bacilli and other microbes, including VapBC, HigBA, MazEF, ParDE, RelBE, MbcTA, PemIK, DarTG, MenTA, one tripartite type II TAC chaperone system, and hypothetical proteins.

The study aims to demonstrate the genes encoded toxin-antitoxin system in mycobacterium tuberculosis strains from clinical samples.

The pulmonary and extra-pulmonary tuberculosis clinical samples were collected, and smear microscopy (Ziehl-Neelsen staining) was performed for the detection of high bacilli (3+) count, followed by nucleic acid amplification assay. Bacterial culture and growth assay, genomic DNA extraction, and polymerase chain reaction were also carried out.

The positive PTB and EPTB samples were determined by 3+ in microscopy smear and the total count of tubercle bacilli determined by NAAT assay was 8.0×100⁵ in sputum and 1.3×10⁰⁴ CFU/ml in tissue abscess. Moreover, the genomic DNA was extracted from culture, and the amplification of Rv1044 and Rv1045 genes in 624 and 412 base pairs (between 600-700 and 400-500 in ladder), respectively, in the H37Rv and clinical samples was observed.

It has been found that Rv1044 and Rv1045 are hypothetical proteins with 624 and 882 base pairs belonging to the AbiEi/AbiEii family of toxin-antitoxin loci. Moreover, the significant identification of TA-encoded loci genes may allow for the investigation of multidrugresistant and extensively drug-resistant tuberculosis.