Tags: Drug.
Tuberculin is an extract of Mycobacterium tuberculosis M. bovis or M. avium that is used in skin testing in animals and humans to identify a tuberculosis infection. Several types of tuberculin have been used for this of which purified protein derivative (PPD) is the most important. PPD is a poorly defined complex mixture of antigens. Tests based upon PPD are relatively unspecific since many of its proteins are found in different mycobacterial species.