Molecular assessment of mycobacterial burden in the treatment of nontuberculous mycobacterial disease

Abstract

IntroductionNontuberculous pulmonary disease causes significant morbidity and mortality. Efforts to tackle infections are hampered by the lack of reliable biomarkers for diagnosis, assessment and prognostication. The aim of this study was to develop molecular assays capable of identifying and quantifying multiple nontuberculous mycobacterial (NTM) species and to examine their utility in following individual patients’ clinical courses.MethodsDNA was extracted from 410 sputum samples obtained longitudinally from a cohort of 38 patients who were commencing treatment for eitherMycobacterium abscessusorMycobacterium aviumcomplex or who were patients with bronchiectasis who had never had positive cultures for mycobacteria. NTM quantification was performed with quantitative PCR assays developed in-house.ResultsThe molecular assays had highin vitrosensitivity and specificity for the detection and accurate quantification of NTM species. The assays successfully identified NTM DNA from human sputum samples (in vivosensitivity: 0.86–0.87%; specificity: 0.62–0.95%; area under the curve: 0.74–0.92). A notable association between NTM copy number and treatment (Friedman ANOVA (df)=22.8 (3), p≤0.01 forM. abscessustreatment group) was also demonstrated.ConclusionThe quantitative PCR assays developed in this study provide affordable, real-time and rapid measurement of NTM burden, with significant implications for prompt management decisions.