Identification of Non-tuberculous mycobacteria isolated from patients at Teaching Hospitals, Kandy and Peradeniya

Abstract

Introduction Non-tuberculous mycobacteria (NTM) are known to cause opportunistic nosocomial infections. The aim of the study was to identify NTM using culture characteristics, biochemical and molecular methods (multiplex PCR) from stored mycobacteria isolated from patients presenting with pulmonary and extra-pulmonary tuberculosis at Teaching Hospitals, Kandy and Peradeniya during a 4-year period from 2004 to 2009.Methods Forty mycobacterial isolates obtained from 48 samples of sputum, urine, broncho-alveolar lavage and peritoneal fluid were analyzed initially by growth characteristics, followed by biochemical and molecular methods for the presence of NTM. Five main growth characteristics were analyzed, which included rate of growth, growth-temperature relationship, production of pigment, colony morphology and growth on McConkey agar. Species identification of these NTM isolates was by performing biochemical tests. Molecular identification was performed by multiplex-PCR technique on mycobacterial clinical isolates for the rapid identification of NTM.Results Of the 40 mycobacterial isolates, 10 were identified as NTM by using culture characteristics and multiplex PCR. All the NTM isolates were identified to species level by biochemical methods and eight species of NTM were identified. These species, obtained from sterile as well as non-sterile clinical samples were identified as M. scrofulaceum, M. haemophilum, M. chelonae, M. kansasii, M. phlei, M. flavescens, M. gastri and M. vaccae. Conclusion Non-tuberculous mycobacteria were isolated from a wide range of sterile and non-sterile clinical samples and contributed to 25% of the mycobacterial isolates in this study. The results of culture characteristics were compatible with the molecular identification (multiplex PCR) differentiating Mycobacterium tuberculosis from non-tuberculous mycobacterial strains. M. kansasii and M. gastri were the most common NTM isolated from clinical isolates.

Keywords

• non-tuberculous mycobacteria, growth characteristics, biochemical identification, multiplex-pcr