Molecular Identification of Rapidly Growing Mycobacteria Isolated from Pulmonary Specimens at a Tertiary Care Hospital in Pondicherry

The prevalence of Rapidly Growing Mycobacteria (RGM) infections has been increasing worldwide. RGM have emerged as important human pathogens that cause a variety of diseases ranging from localized cutaneous infections to disseminated infections. Clinical diagnosis is difficult because there are no characteristic clinical features.

This study was conducted from Aug 2014 to Mar 2017, aimed to identify species of Rapidly Growing Mycobacteria from specimens suspected with pulmonary tuberculosis. We applied conventional biochemical test like growth on the LJ medium containing PNBA (para nitro benzoic acid) to differentiate M.tuberculosis and NTM and PCR-restriction fragment length polymorphism analysis (PRA) of the hsp65 gene for species identification. A 439 bp fragment of hsp65 gene was amplified and digested by two restriction enzymes, BstEII and HaeIII. Digested products were analyzed using polyacrilamide gel electrophoresis.

Thirty seven rapidly growing mycobacteria were isolated and identified by growth characters and conventional biochemical tests. PCR-RFLP of hsp65 gene of 37 isolates revealed M.abscessus 27 (72.9%), M.chelonae 7(18.9%) and M.fortuitum 3 (8.1%).

This study proved that PCR-RFLP of hsp65 gene in Mycobacteria is more sensitive, specific and effective method for identification of NTM at the species level than conventional phenotypic methods.