Investigation of protoplasmic extracts of tubercle bacilli as skin test antigens

Abstract

A protoplasmic extract prepared by mechanical agitation of phenol-killed tubercle bacilli was subjected to differential centrifugation to separate the insoluble intact cells and cellular debris from the soluble fraction. The soluble fraction partially purified by precipitation with ammonium sulfate was used to skin-test guinea pigs sensitized by infection with either M. tuberculosis or mycobacteria other than tubercle bacilli. A high degree of both sensitivity and specificity of reaction was observed when relatively small doses of protein (0.001 and 0.0001 mg) were injected into sensitized animals. Chromatographic fractionation of the partially purified extract on Sephadex G-50 did not increase the sensitivity or specificity of the protoplasmic antigen.