Background: Nontuberculous mycobacteria (NTM) are often detected in patients undergoing treatment for pulmonary tuberculosis. This clinical status is thought to represent NTM disease, contamination, or colonization, but discriminating between these three conditions is difficult.
Purpose: We examined the clinical characteristics and pathogenicity of coexisting NTM among patients with pulmonary tuberculosis, as well as its impact on clinical practice.
Patients and methods: The subjects comprised 59 patients with pulmonary tuberculosis treated at the National Hospital Organization Utsunomiya National Hospital between January and December 2013. Patients in whom NTM was detected in one or more cultures were defined as the NTM group (19 patients), and they were compared to the non-NTM group (40 patients). Antiglycopeptidolipid (anti-GPL) core antibody titers were investigated in 18 patients from the NTM group.
Result: We observed no significant difference in patient characteristics (age, sex, complications, history of pulmonary tuberculosis, lung disease, chest imaging findings, degree of smear positivity on admission) between the two groups. Mean duration of hospitalization was markedly longer for the NTM group, excluding those with coexisting NTM after discharge (98.8 ± 7.9 days), than for the non-NTM group (58.3 ± 3.5 days; p < 0.001). No anti-GPL core antibodies were detected in any of the 18 patients from the NTM group, including 13 patients who fulfilled the ATS/IDSA criteria.
Conclusion: Coexisting NTM observed during treatment for tuberculosis likely results from colonization or contamination and usually has low pathogenicity. However, this finding is related to prolonged hospitalization.