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CC BY-NC-ND 4.0 · J Lab Physicians 2010; 2(02): 089-092
DOI: 10.4103/0974-2727.72157
Original Article

Evaluation of a Rapid Differentiation Test for Mycobacterium Tuberculosis from other Mycobacteria by Selective Inhibition with p-nitrobenzoic Acid using MGIT 960

Babita Sharma
Department of Microbiology, SMS Medical College, Jaipur, India
,
Nita Pal
Department of Microbiology, SMS Medical College, Jaipur, India
,
Bharti Malhotra
Department of Microbiology, SMS Medical College, Jaipur, India
,
Leela Vyas
Department of Microbiology, SMS Medical College, Jaipur, India
› Author Affiliations Source of Support: Nil
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ABSTRACT

Tuberculosis is caused by Mycobacterium tuberculosis (M.tb) as well as Non-tubercular mycobacterium (NTM) with similar clinical presentation. Infections due to NTM are reported to have increased in the past few years. Growth of M.tb is inhibited by p-Nitrobenzoic acid (PNB), whereas, NTM are resistant. One hundred and nine isolates from various clinical samples were identified up to species level by their growth rate, pigmentation, and a battery of biochemical tests, including niacin accumulation, nitrate reduction, and heat-stable catalase (68°C) reactions. Para-nitrobenzoic acid (PNB) inhibition test was performed to differentiate between M.tb and NTM. PNB was added to the Lowenstein-Jensen (LJ) medium and BACTECTM MIGIT (Mycobacteria Growth Indicator Tube)960 medium to a final concentration of 500 μg/ml. All the M.tb isolates, including Mycobacterium tuberculosis H37Rv (standard strain), were inhibited by PNB on both LJ and MGIT 960. Of the NTM isolates, all were resistant to PNB on MGIT 960 and on LJ PNB, except one isolate of Mycobacterium marinum that was resistant to MGIT 960 PNB, but was susceptible to LJ PNB. The reporting time for M.tb ranged from 4–11 days (median 5.9 days) by MGIT 960 and for NTM it was 2–10 days with an average of 4.5 days. This study was carried out to establish the accuracy and efficiency of MGIT 960 PNB and to differentiate between M.tb and NTM.

Keywords

MGIT960 - mycobacterium tuberculosis - non-tubercular mycobacterium (NTM) - p-Nitro-benzoic acid


Publication History

Article published online:
29 January 2020

© 2010.

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