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Year : 2001  |  Volume : 19  |  Issue : 4  |  Page : 230--231

Isolation rates of non-tuberculous mycobacteria from Amritsar

A Agarwal, N Jindal 
 Department of Microbiology, Govt. Medical College, Amritsar - 143 001, India

Correspondence Address:
N Jindal
Department of Microbiology, Govt. Medical College, Amritsar - 143 001

How to cite this article:
Agarwal A, Jindal N. Isolation rates of non-tuberculous mycobacteria from Amritsar.Indian J Med Microbiol 2001;19:230-231

How to cite this URL:
Agarwal A, Jindal N. Isolation rates of non-tuberculous mycobacteria from Amritsar. Indian J Med Microbiol [serial online] 2001 [cited 2020 Jul 6 ];19:230-231
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Full Text

Dear Editor,

The article of Dr. Agarwal “Isolation rates of Mycobacterial species from Varanasi (North India) (Indian J Med Microbiol 2000; 18(4):178-179)”, prompted us to share our observations regarding the isolation of various species of non-tuberculous mycobacteria (NTM) from sputum specimens at Amritsar (Punjab).

A total of 2035 early morning sputum specimens obtained on forceful coughing from patients suffering from various respiratory diseases, attending the clinical departments of medical college, Amritsar were processed for isolation of Mycobacteria. After direct microscopic examination of the Ziehl Neelsen (ZN) stained smears, all the specimens were subjected to decontamination and concentration by modified Petroff's method1 and cultured on a pair of bottles of Lowenstein Jensen (LJ) medium and incubated at 370C for 8 weeks. The slopes were examined every week for the growth of acid fast bacilli (AFB). Once the growth appeared, it was confirmed by ZN staining and screened for NTM by testing tolerance of the isolates to para-nitrobenzoic acid (PNB) in a concentration of 500 mg/mL incorporated in the LJ medium.[2] Species identification of all the NTM was achieved by performing the following tests: rate of growth[2], growth at 250C, 370C and 440C,[2] photochromogenicity,[2] Niacin test,[2] Nitrate reduction test,[2] heat stable catalase,[3] semi quantitative catalase test,[3] and tween hydrolysis (5 and 10 days).[3]

Aryl sulphatase test (3 and 14 days),[2] sodium chloride tolerance test[3] and growth on MacConkey agar were also done.[3] All the patients in whose sputum specimens, NTM were isolated were requested for repeat sputum examination on three different days.

Of the 2035 sputum specimens, 254 showed the growth of AFB on LJ medium. Among these 254, 27 (10.6%) were identified as NTM. The prevalence of NTM varies from country to country and region to region and 10.6% prevalence rate obtained in the present study falls within the range (3.6% to 12.4%) reported in other studies from north west India.[4],[5],[6] Maximum number 40.7% (11/27) of NTM isolates in the present study belonged to Runyon Group III. The most commonly isolated species was M Vacce 22.2% [Table]. However, the majority of isolated species 66.7% () were non pathogens. Paramasivan et al reported 54.6% potential pM vaccae, M gastri, M terrae, M triviale, M gordonae and M szylgaiathogens in their study on NTM.[5]

Only 19 of the 27 NTM positive patients could be followed up. In case of one patient (0.44%) only, same NTM species (M.kansasii) was isolated on three occasions, thus providing it to be the probable cause of the disease, while in rest of the 18 cases NTM appeared to be casual isolates causing transient colonization of the lung.

Isolation of large number of NTM species from the sputum specimens and their presence as casual isolates in majority of patients helped us to conclude that along with the isolation and identification of NTM species it may be important to study its role in the pathogenesis of the disease.


1Chandrasekhan S. Bacteriological and cultural studies on atypical mycobacteria isolated from patients with chronic non-tubercular respiratory disease. Indian J Chest Dis 1973;15:189-194.
2Laidlaw M. In Mackie and McCartney's Practical Medical Microbiology, 13th ed. (Churchill Livingstone, London) 1989; 414.
3Kubica GP. Differential identification of mycobacteria. Am Rev Resp Dis 1973;107:9-12.
4Lal MM, Khan AM, Malhotra RML. Saxena H and Sarkari NBS: Role of anonymous mycobacteria in pathogenesis of human tuberculosis. Ind J Tub 1972; 19: 101.
5Paramasivan CN, Govindar D, Prabhakar R. Species level identification of non-tuberculous mycobacteria from South Indian BCG trial area during 1981. Tubercle 66;9:1985.
6Chakrabarti A, Sharma M, Dubey ML. Isolation rates of different mycobacterial species from Chandigarh (North India). Ind J Med Res 1990;91:11-4.