bacille Calmette-Guérin (BCG) /kalmet″gāran″/ [Léon C.A. Calmette, French bacteriologist, 1863–1933; Camille Guérin, French bacteriologist, 1872–1961] , an attenuated strain of the Mycobacterium bovis bacillus that is given as a live bacterial vaccine to prevent the development of tuberculosis. It is most often administered intradermally, with a multiple-puncture disk. When administered to infants in high-prevalence areas, there is some evidence that it prevents the more serious forms of tuberculosis. It may have some efficacy against leprosy. BCG is also instilled into the bladder as a treatment for bladder cancer to stimulate the immune response in people who have certain kinds of malignancy. It induces a positive tuberculin reaction and may mask early, active infection by removing the diagnostic sign of conversion from the negative to the positive skin reaction. See also tuberculin test, tuberculosis.
