Subbaiah, T V and Mitchison, D A and Selkon, J B
(1960)
The Susceptibility to Hydrogen Peroxide
of Indian and British Isoniazid-Sensitive
and Isoniazid- Resistant Tubercle Bacilli.
Tubercle, 41 (5).
pp. 323-333.
ISSN 0041-3879
Abstract
The present work describes an attempt to modify the method of Kreis and Le
Joubioux (1957a) so that it would accurately estimate the relative proportions of
catalase-positive and catalase-negative organisms in strains containing mixtures of
the two types. A bactericidal test was chosen in preference to a bacteriostatic test,
since it is difficult to obtain quantitative measurement with the latter technique. In
performing a bactericidal test residual peroxide must be inactivated or removed
by dilution so that it does not inhibit the growth of surviving organisms. Knox,
Meadow and Worssam (1956) removed peroxide by centrifugation and washing,
but this method was considered impracticable if this test were to be used on a large scale, and likely to produce inaccurate counts on the surviving organisms. In the
present work the method of removal of peroxide was studied as well as the determination
of the optimal peroxide concentration and period of exposure which would kill
all catalase-negative organisms, but would leave catalase-positive organisms
unaffected. In addition, the method of Kreis & Le Joubioux (1957a) was modified
by reducing the inoculum of organisms exposed to peroxide so that catalase-positive
bacilli would not be able to destroy peroxide during the test itself. The standardised
bactericidal test was then employed in comparing the susceptibility to peroxide of
isoniazid-sensitive strains from British and Indian patients, and in investigating
the relationship between the peroxide susceptibility and the catalase activity of their
isoniazid-resistant mutant strains.
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