Isolation of nontuberculous mycobacteria and Nocardia via mycobacterial culture from pulmonary specimens

Nontuberculous mycobacteria (NTM) and Nocardia are often isolated via mycobacterial culture, yet their prevalence in various pulmonary specimens is uncertain. We retrieved mycobacterial culture results from pulmonary specimens from a tertiary hospital in China between January 2017 and July 2021. The prevalence of non-Mycobacterium tuberculosis (non-Mtb, including NTM and Nocardia) has surpassed Mtb, accounting for 1.7 times the rate of Mtb among all isolates. The frequency of non-Mtb positivity in sputum specimens was significantly higher compared to that in bronchoscopy specimens (3.7% vs 1.9%, P < 0.001). Furthermore, NTM accounted for 59.8% of all Mycobacterium isolates and 42.1% of patients with positive acid-fast staining. Multivariate logistic regression analysis identified several risk factors significantly associated with non-Mtb isolates compared to Mtb, including age over 45 years (adjusted odds ratio [aOR] 2.27), bronchiectasis (aOR 4.52), pulmonary interstitial disorder (aOR 2.11), chronic obstructive pulmonary disease (aOR 1.94), and non-diabetes (aOR 2.10).