It is reported a strong association between INH resistance and virulence of mycobacteria in relation to catalase positive strains and a strong relationship between the low virulence and catalase negative strains.

Find the article by Rahbar et al., IMPORTANCE OF ENZYME IN VIRU CATALASE

LENCE OF ST RAINS OF RESISTANT ISONIAZID Mycobacterium tuberculosis.

This work is very interesting on catalase activity in different mycobacteria, I hope you serve.

http://jb.asm.org/content/92/2/413.full.pdf

No you cannot rule out the presence of NTMs with catalase alone.

While M. tb, M. bovis and M. africanum are all negative for both the thermostable catalase test (68degC) and semi-quantitative catalase test (>45mm), M. marinum and M. haemophilum are also negative for both tests.

Moreover, the type of catalase test used is also important. For instance, M. xenopi, M. avium, M. intracellulare, M. malmoense and M. shimoidei are positive or usually positive for the thermostable catalase test but negative for the semi-quantitative catalase test.

Ref.: Methods in Molecular Microbiology - Vol. 101. Mycobacteria Protocols. Eds. T. Parish and N.G. Stoker. pages 334 and 335.

Thanks very much.

Shane, for ruling out MOTT I would recommend that you that you go for NAP test. NAP negative will definitely rule out any MOTT.

Without MOTTs or NTMs you can not jump to the conclusion that MTB you have is pure.

Thanks everyone

Jeffrey Chen's comment is very important; do you refer to the heat-stable catalase or the semi-quantitative catalase test? Both these tests are not fully reliable and some NTM can test negative for both, so, no, it does not rule out presence of NTM in your sample. In all honesty, biochemical tests (incl NAP) to distinguish NTM from M. tuberculosis complex should be considered obsolete... molecular assays, where available, should be preferred.

Thanks Jakko, I was referring to heat stable. I will be performing molecular assays to detect MOTTs and MTB complex.

you should consider another point also.

clinical isolates of Mycobacterium tuberculosis that are resistant to INH (isoniazide) show reduced catalase activity.

If the mutation underlying the INH resistance is in the catalase/peroxidase system... not all are.

for sure Jakko thanks for your extra explanation

when they catching the Isoniazid resistanse with IS elements, it may be catalase negative, but in nature bacteria(dont have resistance to isoniazid) are positive.

The quality of culture tested is also important. It has to be pure. mutation in catalase-peroxidase gene for INH resistance may also be responsible.