Evaluation of ku gene as a differential biomarker for rapid molecular detection of Mycobacterium tuberculosis complex using a real-time PCR assay

currently TB diagnosis is limited by some major limitations in low-income and less experienced hospitals. Recently, it has been proposed that the ku gene of mycobacterial strains has the potential to be a highly specific and sensitive candidate biomarker for molecular detection of Mycobacterium tuberculosis (Mtb). This study was aimed to evaluate the specificity and sensitivity of a real-time PCR assay for detection of ku gene in Mtb complex to determine its applicability for Mtb identification.

The identification of Mtb was confirmed using GeneXpert assay. Specific primers for ku gene were designed and the cycle threshold (Ct) value from the real-time PCR was used as a proxy measure of the cut-off point. Receiver operating characteristic (ROC) curve analysis was conducted to determine the diagnostic performance of ku gene in detecting Mtb directly from clinical specimens.

ku amplification was interpreted as positive and negative based on Ct values, in which a value <38 was considered positive and a value >40 was considered negative. Our findings revealed that the ku gene was found to be distributed in all Mtb-positive samples. Of note, none of the Mtb-negative exhibited a specific signal in a maximum of 40 cycles.

The ku gene amplification using real-time PCR indicated high sensitivity and specificity for the detection of Mtb complex in sputum samples.