Profiles of skin test reactivity to antigens of various mycobacterial species in a human population and in experimental infections

Abstract

Sensitivity profiles to 6 mycobacterial skin test antigens prepared from Mycobacterium tuberculosis, M. kansasii, M. scrofulaceum, M. intracellulare, M. avium and M. fortuitum were obtained in 6 groups of guinea pigs, each infected with one of the 6 mycobacterial species. Each group of animals showed the greatest sensitivity towards the homologous antigen. A second infection with a different species was super-imposed two months after the skin tests; the sensitivity towards the second species usually became dominant. Sensitivity profiles with the 6 antigens in a large random sample of the population of a district of Haiti resembled closely the sensitivity profiles for all the guinea pigs infected with two mycobacterial species. This suggested that the Haitian population consisted of a mixture of persons infected with one or more mycobacteria. Haitians with the largest reaction to an antigen, which was at least 6 mm in diameter and at least 2 mm larger than the reaction to any other antigen, were assumed to be infected with the corresponding mycobacterial species. Sensitivity profiles of these persons resembled closely the sensitivity profiles of guinea pigs infected with the same species. In the Haitian population prevalence of infection with other mycobacterial species was much more common than infection with M. tuberculosis. In spite of this, after 15 years of age only the tuberculosis infection rates increased with age, suggesting that allergy produced by M. tuberculosis infection was stronger and subject to much less waning than allergy produced by other mycobacterial infections.