Prevalence of nontuberculous Mycobacterial infection in Non-HIV subjects of clinically presumed tuberculosis at a tertiary care center, Hyderabad

Abstract

Introduction: Tuberculosis continues to be the leading cause of morbidity and mortality in developing nations. Off late infections due to mycobacterial species other than tubercle bacilli are being reported frequently. Nontuberculous mycobacteria are being increasingly recognized and isolated as pathogens from immunocompetent host too. They are found in both pulmonary and extrapulmonary form of disease. The prevalence of infections due to NTM is known to vary with place, host and climatic factors. Aim: the present study is a retrospective cross-sectional observational study for a period of two years from Jan.2013- Dec.2014, at Princess Era Hospital,a teaching hospital of Deccan college of medical sciences at Hyderabad. Data from microbiology lab records was retrieved and analysed. Materials and Methods: about 232 specimens from 229 patients with clinical symptoms of tuberculosis were analysed for laboratory diagnosis of nontuberculosis mycobacterial infection in mycobacteriology section of microbiology laboratory. Seventy nine samples were obtained from 78 patients with pulmonary form of disease and 153 samples were from 151 patients with extrapulmonary form of disease. Study was approved by ethical committee of the college and patient consent was obtained prior to sample collection. All the specimens received in the laboratory were processed by direct microscopy for acid fast bacilli using Ziehl Neelsen stain. Culture was performed on conventional LJ media and Middle Brook 7H12 media in MGIT 320 automated system. Identification of culture positive isolates was achieved by standard biochemical test and rapid immunochromatography test for detection of mycobacterial tuberculosis protein 64 antigen [MPT64]. Results: Direct microscopy was positive in 20.52%. and 4.25% of which were later identified as NTM. Culture yielded positive result in 22.27% of the subjects. NTM were isolated in 3.49% of the total subjects studied. Mycobacterium tuberculosis was the most common