Attenuated tuberculin skin test responses associated with Mycobacterium intracellulare sputum colonization in an adolescent TB prevalence survey in Western Kenya

Introduction

Exposure to Non-tuberculous Mycobacteria (NTM) varies regionally and may partly explain the disparate outcomes of BCG vaccination and tuberculosis (TB) susceptibility.

Methods

We examined NTM sputum colonization, associations with clinical characteristics, and tuberculin skin test (TST) responses in an adolescent TB prevalence survey.

Results

Among 5004 adolescents screened, 2281 (45.5 %) were evaluated further. TB and NTM prevalence rates were 0.3 % and 8.0 %, respectively. Among 418 NTM isolates, 103 were unidentifiable, and 315 (75 %) comprised 15 species, the most frequent being M. intracellulare (MAC) (108, 26 %), M. scrofulaceum (96, 23 %) and M. fortuitum (51, 12 %). “NTM colonized” adolescents had less frequent chronic cough and night sweats (adjusted odds ratio [aOR] 0.62, 95 % confidence interval [CI] 0.44-0.87and aOR 0.61, CI 0.42–0.89 respectively), and lower TST induration (median 11 mm (interquartile range [IQR] 0–16) vs 13 mm (IQR 6–17; p = 0.006)) when compared to “NTM not colonized” participants. MAC, but not M. scrofulaceum or M. fortuitum, was associated with decreased TST induration (median 7.5 mm (IQR 0–15) vs 13 mm (IQR 6–17) among “MAC colonized” vs “not colonized”, p = 0.001).

Conclusion

We observed high NTM prevalence rates with species-specific associations with TST induration, consistent with a model of species-dependent heterologous immunity among mycobacteria.