|A COLD STAINING METHOD FOR TUBERCLE BACILLI USING
|K Padmanabha Rao, N Naganathan & SS Nair: Indian
J TB 1966, 14, 3-9.
The difficulty in staining tubercle bacilli is
believed to be related to the complex surface structure containing
a large amount of unsaponifiable wax. Any staining technique which
can counteract the influence of this wax could therefore be expected
to give better results. The standard method in vogue is the application
of heat which renders the bacilli permeable to aqueous dyes. Several
attempts have been made to develop a cold staining method for tubercle
bacilli as for other organisms. Since this wax is soluble in chloroform,
a cold staining method using carbol fuchsin containing chloroform
was developed and the results of staining by this new method have
been compared with the conventional Ziehl-Neelsen (ZN) method in
the present study. Triplicate smears were made from 186 specimens
and these were stained by ZN, Cold Staining (CS) and Fluorescent
Microscopy (FM) methods. In addition, single smears of 343 specimens
previously examined by FM were randomly divided into two subgroups
and restained by ZN and CS methods respectively.
The results of examination of duplicate smears
by ZN and CS methods showed a high degree of correlation
with 75%(140/186) showing identical grading and only 8 were positive
by one and negative by the other method. Of the 8 smears positive
by CS alone, 7 were confirmed by culture, whereas 3 were positive
by culture out of the 8 positive by ZN method. This indicates that
those positive by CS alone are likely to be real cases, whereas
those positive by ZN alone may include some false positive cases.
As far as false negatives are concerned, there was no difference
between ZN and CS methods. The reliability of these methods was
judged on the basis of culture results and agreement among themselves.
The cold staining method was found to be as efficient as ZN method
in detecting different gradings of culture positives. In addition,
preparation of stain, training of personnel for CS was also found
to be as simple as ZN method.
|KEY WORDS: STAINING METHODS, COLD STAINING,
TUBERCLE BACILLI, ZIEHL1-NEELSEN, FLUORESCENT.