Figure 1.

The proposed algorithm for diagnosing and managing nontuberculous mycobacteria pulmonary disease. A second independent sputum sample (ideally taken ≥1 week after the initial sputum sample) is requested if the first sputum is culture-positive for NTM in a patient with a clinical and radiological picture consistent with pulmonary NTM disease. In cases of inconclusive or negative results from molecular testing and when smear microscopy is negative for AFB, sputum culture should be performed on that specimen. In addition, if the NTM identified with a direct molecular method from the sputum correlates with the NTM isolated on the initial sputum culture, susceptibilities can be performed from the culture. The clinician can consider treatment or the watchful wait management approach without needing a second culture.

AFB, acid-fast bacilli; NTM, nontuberculous mycobacteria.

Footnote:

^@ Active pulmonary tuberculosis must be excluded using a standard diagnostic algorithm that includes a GeneXpert MTB/RIF Ultra negative in most settings.

^$ In cases with an isolated culture that signals NTM growth, the clinician must ensure that the results correlate with the clinical and radiological profile consistent with NTM pulmonary infection.

^# Direct molecular testing will only be performed depending on the availability of the appropriate assay suitable to detect the NTM that was cultured using the initial sputum sample.

* A second culture must be sent for discordance between direct molecular testing and initial culture results.

^ Microbiological treatment response can be evaluated using serial cultures/smears. These must be evaluated in conjunction with the clinical and radiological response to treatment.

** Many NTM species may not cause significant pulmonary disease (low pathogenic potential), e.g., M. gordonae, M. mucogenicum, M. nonchromogenicum, M. haemophilum, M. flavescens, M. gastri, M. terrae, or M. triviale. Thus the ‘watchful waiting’ strategy may be applied with adequate patient follow-up, incorporating clinical and radiological parameters.