Abstract and Introduction
Nontuberculous mycobacteria (NTM) can cause chronic pulmonary infection in susceptible hosts. Individuals with cystic fibrosis (CF), a multisystem disease predominated by progressive structural lung disease, are particularly vulnerable. Only recently have NTM been recognized for their potential to cause lung deterioration in CF patients. The reported prevalence varies widely from 4 to 40%, significantly more common than in the general population, but this varies because of multiple factors including inconsistent screening practices. Mycobacterium abscessus complex and Mycobacterium avium complex are the two most common species recovered. Defining NTM pulmonary disease in a CF patient can present challenges as it can be difficult to distinguish from the other potentially pathogenic organisms in the lung microbiome. In general, treatment regimens do not differ from the non-CF population but the clinician should be aware of potential interactions with other CF therapies. Recent population-level genomics has raised serious concern for indirect person-to-person transmission of several dominating NTM clones worldwide, raising awareness for increase prevention strategies when CF patients potentially congregate, such as clinic visits. Lung transplantation is controversial in those with NTM present in sputum culture but the available evidence suggests that this is not an absolute contraindication.
Cystic fibrosis (CF) is a multisystem disease caused by a mutation in the cystic fibrosis transmembrane conductanc eregulator (CFTR) gene, which regulates ion transport and results in impaired mucociliary clearance. This renders the airways susceptible to persistent infection, excessive inflammation, and progressive structural lung changes. Bacterial pathogens (e.g., Pseudomonas aeruginosa) are most prevalent in the airways of CF patients, but recently there has been greater attention to nontuberculous mycobacteria (NTM), which are becoming recognized as a relevant cause of lung deterioration.[1,2]
NTM are ubiquitously found in the environment such as water, soil, milk, and animals, and in particular gravitate toward aquatic biofilms.[3–6] In the general population, about 50% who grow NTM from their respiratory culture will develop pulmonary disease believed to be attributable to NTM. Why some individuals seem to clear the organism without demonstrable infection is not known, but it is intuitive that CF patients have greater vulnerability for persistence of NTM in the airways, because of the structural disease and impaired mucociliary clearance. The persistence of NTM in cultures of respiratory specimens alone is insufficient to define NTM pulmonary disease (NTM-PD). CF patients typically meet criteria for NTM-PD established in published guidelines, so recent recommendations suggest treatment of other pathogens and comorbidities first before making the diagnosis of NTM-PD. Here, in this article, we will discuss the burden of NTM in the CF population, challenges to establishing a diagnosis, how treatment may vary in CF patients from the general population, potential horizontal transfer between CF patients, and, lastly, the impact NTM infection can have on lung transplant candidacy.
Semin Respir Crit Care Med. 2018;39(3):383-391. © 2018 Thieme Medical Publishers