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Delayed type hypersensitivity

A term to encompass cell-mediated immune reactions that are detectable by skin testing. They are termed delayed as they take longer to appear than various antibody-mediated hypersensitivity reactions characteristic of allergic conditions. The positive tuberculin test is a typical example of a delayed hypersensitivity as it takes around 48 hours to develop.

Directly observed therapy (DOT)

Administration of anti-tuberculosis drugs under direct supervision. One of the elements of the World Health Organization DOTS strategy.

Directly Observed Treatment Shortcourse (DOTS)

The ‘brand name’ of the World Health Organization’s recommended strategy for TB control.  The components are:
•    Political commitment with increased and sustained funding
•    Case detection through quality assured bacteriology: including strengthening TB laboratories and surveillance for drug-resistance.
•    Standardised multi-drug treatment delivered free to each patient through Directly Observed Therapy
•    An active drug supply and management system: secure supply of good quality drugs
•    Monitoring, evaluation and impact measurement: individual patient outcome evaluation to ensure cure and cohort evaluation to monitor overall programme performance.

The strategy is credited with being an inexpensive and highly effective means for treating patients already infected with TB and to prevent new infections and the development of drug resistance.

Disease ratio

The ratio of those infected with, for example, the tubercle bacillus and those actually developing the disease.

Disseminated Tuberculosis

Tuberculosis that has spread from the original site of infection to involve many organs and tissues. There are two named types – Cryptic Disseminated and Miliary.

DNA (deoxyribonucleic acid)

The famous ‘double helix’ forming the molecular structural basis of genes and chromosomes.
DNA fingerprinting

A technique used to divide a species, such as Mycobacterium tuberculosis, into many variants by detecting small differences in their DNA structure. This enables the spread of these variants in the community to be studied for epidemiological purposes.


See Directly Observed Treatment Shortcourse.

A modification of the DOTS strategy to manage multi-drug resistant tuberculosis.

Drug interactions

The effect of one drug on the absorption, metabolism and activity of another.  Several important drug interactions occur between rifampicin and other drugs, especially antiretroviral drugs given to those infected with HIV.

Drug reactions

See side effects.
Drug resistance

A mutational event in the bacterial cell leading to resistance to an anti-tuberculosis drug. Drug resistance is determined in the laboratory by growing isolated tubercle bacilli on media containing various concentrations of the drug.


Difficulty in swallowing.


Painful or difficult urination.

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