Nontuberculous Mycobacterial Lung Disease in the Patients with Cystic Fibrosis-A Challenging Diagnostic Problem

Background: Cystic fibrosis (CF) is an autosomal, recessive genetic disorder, caused by a mutation in the cystic fibrosis transmembrane conductance receptor regulator (CFTR) gene. Dysregulated mucous production, and decreased bronchial mucociliary clearance, results in increased susceptibility to bacterial and fungal infections. Recently, nontuberculous mycobacteria (NTM) infections were identified as an emerging clinical problem in CF patients. Aim: The aim of the present study was to assess the frequency of NTM isolations in CF patients hospitalized in the pulmonary department, serving as a hospital CF center, and to describe challenges concerning the recognition of NTMLD (nontuberculous mycobacterial lung disease) in those patients. Methods: Consecutive CF patients, who were hospitalized due to pulmonary exacerbations (PEX), in a single CF center, between 2010 and 2020, were retrospectively assessed for the presence of NTM in respiratory specimens. Clinical and radiological data were retrospectively reviewed. Results: Positive respiratory specimen cultures for NTM were obtained in 11 out of 151 patients (7%), mean age-35.7 years, mean BMI-20.2 kg/m(2), mean FEV1-58.6% pred. Cultures and phenotyping revealed the presence of Mycobacterium avium (M. avium)-in six patients, Mycobacterium chimaera (M. chimaera) in two, Mycobacterium kansasii (M. kansasii)-in one, Mycobacterium abscessus (M. abscessus)-in one, Mycobacterium lentifavum (M. lentiflavum)-in one. Simultaneously, respiratory cultures were positive for fungi in 91% of patients: Candida albicans (C. albicans)-in 82%, Aspergillus fumigatus (A. fumigatus)-in 45%. Clinical signs of NTMLD were non-specific, chest CT indicated NTMLD in five patients only. Conclusion: Due to non-specific clinical presentation, frequent sputum cultures for NTM and analysis of serial chest CT examinations are crucial for NTMLD recognition in CF patients. Further studies concerning the predictive role of fungal pathogens for NTMLD development in CF patients are needed.