[Indications for chemoprophylaxis of tuberculosis. Arguments for].

After a first infection with M. tuberculosis, reactivation of the disease may be prevented by chemoprophylaxis with isoniazid or rifampicin. Such chemoprophylaxis should be administered to all subjects with an immune defect due to HIV infection, immunosuppressors, severe diabetes, renal insufficiency or silicosis. Extensive sequelae of tuberculosis on chest X-ray are also a major risk of reactivation without treatment. Tuberculosis is most likely to become active during the first three years following first infection for an healthy subject. However, beyond this limit or when the time of infection is unknown, the most objective decisional analysis still demonstrates the clear-cut benefit of chemoprophylaxis in proportion to its side effects for all young subjects aged less than 35 years.