resistance is the emergence and spread of “Multi Drug Resistant TB (MDRTB)”. It is a global problem and its presence in those with concomitant HIV infection makes
Not all infected persons show the clinical symptom.
10–20% are asymptomatic. It is important to differentiate
between TB infection and TB disease to understand this.
TB Infection and Disease: Differentiation
Tuberculin skin test Positive Positive
Sputum: Smear/culture Negative Positive for bacilli
Symptoms No symptoms Cough, fever,
Infectious Not infectious Infectious before
The diagnosis of TB infection and disease can be made
clinically with symptoms. The laboratory diagnosis of
tuberculosis may be established by demonstrating the
bacillus in the lesion by microscopy, isolating it in culture
or by transmitting the infection to experimental animals.
Immunological response to the disease can be made by
demonstrating of hypersensitivity to tuberculoprotein.
Serological response to mycobacterial antigens in serum
Many methods have been described for tuberculin
testing. The method used routinely is the technique of
Mantoux. In this 0.1 mL of PPD containing 5TU is injected
intradermally. A positive test indicates hypersensitivity
to tuberculoprotein denoting infection with TB bacilli or
BCG vaccination. Persons who have never had contact
with tubercle bacilli are tuberculin negative.
Pitfalls of Laborartory Diagnosis
Even there are many laboratory methods, there are many
pitfalls in accurate diagnosis.
Non-specificity: Microscopy, in spite being a rapid test
suffers from specificity due to poor staining and also lack
of species identification. Saprophytic mycobacteria may
give false results. In fluorescent microscopy, background
fluorescence can give false positive results.
Time: Culture, being one of the confirmatory methods
for diagnosis is time consuming. It takes 6–8 weeks for a
culture report. Species identification will take more time.
The clinician must start empirical treatment and wait for
is started, the patient may not respond. This will lead to
waste of time and money from the patient and clinician
False negativity: Skin testing may be false negative
(anergy) due to impaired immune response. Also
infection by atypical mycobacteria may interfere with the
Importance of Serological Diagnosis
¾ One of the most extensively researched areas
¾ Very important tool for diagnosis in smear negative
¾ IgG, IgM, IgG antibodies have been found to be useful
¾ It is sensitive and specific
¾ It is rapid and cost effective
¾ Antibody patterns correlates with the clinical condition.
Chemotherapy has revolutionized the management of
tuberculosis. Antituberculosis drugs are of two types,
bactericidal and bacterostatic
Bactericidal: Rifampicin, pyrazinamide, isoniazid and
They can also be classified as first line and second line
The major problem in chemotherapy is drug resistance,
which in tubercle bacilli is due to mutation, with an
approximate rate of once in 108
Drug resistance may be “primary” (pretreatment,
initial), when the patient is infected with a strain of tubercle
bacillus which is already drug resistant or “acquired”
(secondary, post-treatment), when the infecting strain
initially sensitive becomes resistant, usually as a result
of improper or inadequate treatment. This is the more
A very serious consequence of unchecked drug
resistance is the emergence and spread of “Multi Drug
Resistant TB (MDRTB)”. It is a global problem and its
presence in those with concomitant HIV infection makes
RAPID TEST FOR DETECTION OF ANTIBODIES
TO MYCOBACTERIUM TUBERCULOSIS (DEVICE)
(Courtesy: Tulip Group of Companies)
Serocheck-MTB is a rapid, self performing, qualitative, two
site sandwich immunoassay for the detection of antibodies
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