Non tuberculous mycobacteria isolated from clinical specimens at a tertiary care hospital in South India

Abstract

Purpose: This is a retrospective analysis of the isolation rates of nontuberculous mycobacteria (NTM) from various clinical specimens and their antimicrobial susceptibility patterns. Methods: All NTM isolated between 1999 and 2004 at Christian Medical College, Vellore, South India, were identified with various biochemical tests. Antimicrobial susceptibility test for all NTM was performed by standard methods. Results: A total of 32,084 specimens were received for culture, of which 4473 (13.9%) grew acid fast bacilli (AFB). Four thousand three hundred (96.1%) of the AFB were M. tuberculosis while 173 (3.9%) were NTM. Of the 173 NTM, 115 (66.5%) were identified to the species level. Pus, biopsy specimens and sputum specimens yielded most of the NTM of which M. chelonae (46%) and M. fortuitum (41%) accounted for majority of them. M. chelonae and M. fortuitum, showed highest susceptibility to amikacin (99.2%). NTM were repeatedly isolated from seven sputum specimens, 15 biopsy and pus specimens, two CSF and two blood cultures. Six were isolated from patients with AIDS and five from post transplant patients. Conclusions: The isolation of NTM from various clinical specimens is reported in this study to highlight the associated diseases and therapeutic options in these infections. 1 NTM comprising of over 95 species are naturally seen as saprophytes 2 but are known to cause four different categories of infections in humans such as, i) pulmonary infections resembling tuberculosis, ii) extra pulmonary infections affecting lymph nodes, skin and soft tissue, iii) multifocal disseminated infections and iv) infections in immunocompromised individuals such as AIDS and transplant patients.3 The growing population of HIV infected individuals and other immunosuppessed / immunocompromised patients coupled with better diagnostic techniques has led to an increase in the number of NTM being reported in human infections in recent years. 4 NTM produce infections more commonly in the presence of predisposing factors / underlying diseases; they are also notably resistant to commonly used antitubercular drugs. These factors augment morbidity and limit therapeutic options in such infections. NTM have been reported world wide with varying frequencies, 5-8 while in India isolation rates are between 0.7% and 34%. 9 We have reviewed the isolation rates of NTM from various clinical specimens over a period of six years at the department of Clinical Microbiology, Christian Medical College, Vellore -South India. Through this study we wish to emphasize the need to look for NTM in various clinical specimens. Materials and MethodsThis study includes the isolation of NTM from all clinical specimens from suspected pulmonary and extra pulmonary tuberculosis received between 1999 and 2004. Early morning well coughed out sputum specimens, broncho alveolar lavage, bronchial wash and endotracheal aspirate specimens were received from patients with clinical and radiological findings suggestive of pulmonary tuberculosis. From children and patients fro...

A laboratory-based study to identify and speciate non-tuberculous mycobacteria isolated from specimens submitted to a central tuberculosis laboratory from throughout KwaZulu-Natal Province, South Africa

“…The incorrect diagnosis leads to unnecessary and/or incorrect treatment of many patients who are in fact colonised or infected with NTM. [9] The most common species of NTM identified during the study period was M. intracellulare (45.9%), followed by M. avium ssp. (11.3%).…”

Antimicrobial susceptibility testing of rapidly growing mycobacteria by microdilution -$$$ Experience of a tertiary care centre

“…In a study on nontuberculous mycobacteria isolated from a tertiary care centre in S. India, MV Jesudasan and P Gladstone reported 100 (2.23%) isolates of M. chelonae and M. fortuitum out of 4473 mycobacterial isolates. [6] However, the predominant isolate was M. chelonae. Unlike our study their study had also included pulmonary specimens.…”

Nontuberculous Mycobacteria in Respiratory Tract Infections, Eastern Asia

“…Regardless of clinical relevance, 25 articles reported on NTM isolates from pulmonary samples (Figure 1) (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(17)(18)(19)(20)(21)(22)(25)(26)(27)(28)(29)(30)(31)(32)(33) (5,(25)(26)(27)(28)(29). The overall isolation of RGM in this part of Asia was 16%, making RGM the second most frequently isolated species in this region.…”