The extent and importance of sensitization by opportunist mycobacteria in Lagos, Nigeria.

3505 school children aged 6 to 15 years were tested with PPDS and at the same time one of the following tuberculins, namely, PPDG, PPDPL, PPDA, PPDF and PPDY. The tuberculins were prepared from human tubercle bacillus, the Gause organism, M. marinum, M. avium, M. fortuitum and M. kansasii respectively. PPDY, PPDA and PPDG gave more reactions of greater than 2 mm induration than did PPDS. Furthermore, tests with PPDY, PPDA, PPDG and PPDPL showed a significant proportion of children with reactions of 10 mm or more, suggesting that many of them had been sensitized to these antigens, particularly in the older age groups. The tuberculin sensitivity profile of these children resembled that found for a small community in Georgia, U.S.A., which had been studied previously. The profile also resembled that of guinea pigs which had been experimentally infected with the Gause organism. This supports the conclusion that a high proportion of these children had past or present infection with either the Gause organism or antigenically related mycobacteria. Finally, PPDS gave the highest percentage of children who had reactions greater than 10 mm. It is suggested that 10 mm might be a useful size of induration to divide opportunist mycobacterial infection from infection by M. tuberculosis in Lagos.