Nontuberculous mycobacterial and Nocardia infections mimicking pulmonary tuberculosis: A retrospective study of a general hospital patient population in China

Abstract

Purpose. In this study, we differentiated between tuberculosis (TB) and infections caused by nontuberculous mycobacteria (NTM) or Nocardia in a tertiary general hospital in China. Differences in clinical manifestations and factors between respiratory infections associated with these organisms were also investigated. Methodology. A retrospective analysis was conducted for suspected pulmonary TB patients with positive bacterial culture results under treatment at Wangjing Hospital, a tertiary general hospital, between January 2014 and June 2017. Sputum samples were submitted for liquid culture and species identification by mass spectrometry. Results. Between January 2014 and June 2017, a total of 3981 suspected TB cases were analysed, of which 151 (3.8%) exhibited positive mycobacterial culture results. Using mass spectrometry, the 151 isolates were classified into three groups: Mycobacterium tuberculosis (MTB) (n=112; 74.2%), NTM (n=21 13.9%) and Nocardia (n=18; 11.9%). The NTM and Nocardia prevalence rates were significantly higher amongst elderly patients [aged ≥65 years; odds ratio (95% confidence interval): 3.89 (1.05-14.38) for NTM; odds ratio (95% confidence interval): 5.10 (1.09-23.91) for Nocardia]. In addition, treatment with immunosuppressive therapy [odds ratio (95% confidence interval): 3.92 (1.16-13.27)] was identified as a risk factor for Nocardia infection in these patients. Conclusion. Our results demonstrated that a quarter of culture-positive 'suspected TB patients' harboured NTM or Nocardia infections. Notably, nearly all patients with non-TB infections presented with clinical syndromes mimicking pulmonary TB. Individuals receiving immunosuppressive therapy were at greater risk of acquiring Nocardia infections.