Detection and identification of non-tuberculous mycobacterial infections in 6,472 tuberculosis suspected patients

Between March 1993 and March 1994, 82 patients with infection by non-tuberculous mycobacteria (NTM) and 443 patients with tuberculosis (TB) were registered among 6,472 patients with suspected tuberculosis. Skin-test reactivity to purified protein derivative (PPD) in patients demonstrated indurations of 10-14 mm or more for the majority of patients in both groups. Most patients with NTM infection had abnormal chest roentgenograms shoeing sporadic infiltrations, nodular abscesses, and cavities resembling TB radiological evidence. The similarity in age range, PPD skin reaction, and radiological evidence in patients infected with NTM or Mycobacterium tuberculosis (MTB) can mislead the physician. Some NTM species were recovered more often than others: Mycobacterium fortuitum from 22 clinical specimens (26.8%); Mycobacterium gastri 19 (23.1%); and Mycobacterium terrae complex 15 (18.3%). The antimicrobial drug susceptibility tests of the isolated organisms showed that 42 (9.5%) isolates of MTB were resistant to isoniazid and 31 (7.0%) to streptomycin. A few strains (1.3%) were identified as being resistant to a combination of 3 primary drugs. These findings suggest that drug-resistant mycobacterial infections are becoming an important problem in the region.