Specific amplification of gene encoding N-terminal region of catalase–peroxidase protein (KatG-N) for diagnosis of disseminated MAC disease in HIV patients

• M. avium katG-N PCR accurately and rapidly detected MAC bacteremia in HIV patients.
• M. avium katG-N PCR positivity correlated 100% with biochemical identification.
• M. avium katG-N was more sensitive than IS1245 in detecting true avium organism.

Disseminated Mycobacterium avium-intracellulare complex (MAC) infection is considered as severe complication of advanced HIV/AIDS disease. Currently available various laboratory investigations have not only limited ability to discriminate between MAC infection and tuberculosis but are also laborious and time consuming. The aim of this study was, therefore, to design a molecular-based strategy for specific detection of MAC and its differentiation from Mycobacterium tuberculosis (M. tb) isolated from the blood specimens of HIV patients. A simple PCR was developed based on the amplification of 120-bp katG-N gene corresponding to the first 40 amino acids of N-terminal catalase–peroxidase (KatG) protein of Mycobacterium avium that shows only ~13% sequence homology by clustal W alignment to N-terminal region of M. tb KatG protein. This assay allowed the accurate and rapid detection of MAC bacteremia, distinguishing it from M. tb in a single PCR reaction without any need for sequencing or hybridization protocol to be performed thereafter. This study produced enough evidence that a significant proportion of Indian HIV patients have disseminated MAC bacteremia, suggesting the utility of M. avium katG-N gene PCR for early detection of MAC disease in HIV patients.