Skin test reactivity to mycobacterial antigens parallels the phylogenetic structure of their genus

SETTING: City of Manaus, Amazonas, Brazil. OBJECTIVE: To explore the relati onship between positivity to tuberculin and other environmental mycobacteri a sensitins, according to a range of criteria and presence of BCG scar. DES IGN: Dual skin testing with tuberculin and four mycobacterial sensitins, an d BCG scar recording of 1070 schoolchildren aged 7-14. Four criteria for po sitivity were used: simple and dominant, with 5 and 10 mm cut-off points. R ESULTS: The standardised prevalence of reactions greater than or equal to5 mm for BCG scar negative children was 58.3% Mycobacterium avium, 54.2% for M. scrofulaceum, 26.8% for M. fortuitum, 27.3% for M. tuberculosis and 7.6% for M. kansasii. Correlations between tuberculin and each sensitin, for BC G scar negative children, were 0.47 for M. avium, 0.53 for M. scrofulaceum, 0.60 for M. kansasii and 0.22 for M. fortuitum (all with P < 0.01). BCG ef fect was particularly significant for tuberculin (odds ratio = 3.44 for rea ctions greater than or equal to5 mm, P < 0.001) and influenced the balance between dominant/non-dominant reactions for all sensitins. CONCLUSION:: The correlation between tuberculin and each sensitin confirmed the separation of the rapidly (M. fortuitum) and slowly growing mycobacteria (M. tuberculo sis, M. avium, M. scrofulaceum and M. kansasii. The influence of BCG on tub erculin reactions was more marked than on other mycobacterial sensitins.