Identification of nontuberculous mycobacterial infection by IS6110 and hsp65 gene analysis on lung tissues

The clinical, histologic, and radiographic presentations of nontuberculous mycobacterial (NTM) lung disease are usually indistinguishable from those of reactivated pulmonary tuberculosis (TB), so it remains a great challenge for the clinician to make treatment decisions for patients with old TB and a positive culture result for NTM. This study investigated whether the mycobacterial specific heat shock protein 65 (hsp65) and Mycobacterium tuberculosis (MTB)-specific IS6110 gene would present in pulmonary lesions of patients with NTM pulmonary infection. Formalin-fixed and paraffin-embedded (FFPE) tissue blocks of 24 patients with NTM infections treated at the hospital from 1998 to 2008 were included. Mycobacterial hsp65 gene was amplified in 20 of the 24 patients, and the species identified by sequencing was consistent with corresponding culture results in 12 of these patients. MTB-specific IS6110 gene was detected in 3 of the 7 patients who had old TB and a subsequent diagnosis of fibrocavitary NTM lung disease. Polymerase chain reaction (PCR) analysis of hsp65 gene also confirmed the presence of MTB genes in 2 of these 3 patients. Our results indicate that PCR amplification and sequencing of the mycobacterial hsp65 gene is a sensitive assay for identification of NTM species in FFPE materials. However, consistent results of PCR analysis, microbiology study, histologic manifestations, radiology, and clinical presentation are important for correct diagnosis of NTM pulmonary infection. The presence of MTB gene in patients with fibrocavitary NTM lung lesions poses a clinical dilemma for deciding concurrent treatment TB and NTM infection.