Antibiotic management of lung infections in cystic fibrosis. II. Nontuberculous mycobacteria, anaerobic bacteria, and fungi

Abstract

Airway infections are a key component of cystic fibrosis (CF) lung disease. Whereas the approach to common pathogens such as Pseudomonas aeruginosa is guided by a significant body of evidence, other infections often pose a considerable challenge to treating physicians. In Part I of this series on the antibiotic management of difficult lung infections, we discussed bacterial organisms including methicillin-resistant Staphylococcus aureus, gram-negative bacterial infections, and treatment of multiple bacterial pathogens. Here, we summarize the approach to infections with nontuberculous mycobacteria, anaerobic bacteria, and fungi. Nontuberculous mycobacteria can significantly impact the course of lung disease in patients with CF, but differentiation between colonization and infection is difficult clinically as coinfection with other micro-organisms is common. Treatment consists of different classes of antibiotics, varies in intensity, and is best guided by a team of specialized clinicians and microbiologists. The ability of anaerobic bacteria to contribute to CF lung disease is less clear, even though clinical relevance has been reported in individual patients. Anaerobes detected in CF sputum are often resistant to multiple drugs, and treatment has not yet been shown to positively affect patient outcome. Fungi have gained significant interest as potential CF pathogens. Although the role of Candida is largely unclear, there is mounting evidence that Scedosporium species and Aspergillus fumigatus, beyond the classical presentation of allergic bronchopulmonary aspergillosis, can be relevant in patients with CF and treatment should be considered. At present, however there remains limited information on how best to select patients who could benefit from antifungal therapy.

Keywords: Aspergillus fumigatus; Mycobacterium abscessus; Mycobacterium avium complex; Scedosporium species complex; anaerobic bacteria.

Figure 1.

Determining treatment of nontuberculous mycobacteria (NTM) lung disease requires assessment of diagnostic strategies, treatment options, and individualized risk–benefit analyses. When deciding whether to treat a patient with NTM lung disease, the risk and benefits of treatment must be weighed against observation. This decision is influenced by many factors including the risk of progression, goals of therapy, and patient factors. Po = per os (by mouth).

Figure 2.

Cystic fibrosis fungal biodiversity grouped according to frequency of isolation (x axis) and established pathogenicity (y axis). The fungi are further divided in terms of chronicity as illustrated. The most frequently isolated filamentous fungi, Aspergillus fumigatus and Scedosporium species complex, and yeast Candida albicans are highlighted and further discussed in text. Low-chronicity genera: A. = Aspergillus; C. = Candida; E. = Exophiala; P. = Pneumocystis; R. = Rasamsonia. High-chronicity genera: A. = Aspergillus (flavus, nidulans, niger); A. = Acrophialophora (fusispora); C. = Candida; E. = Exophiala; N. = Neosartorya; P. = Pseudallescheria; S. = Scedosporium; T. = Trichosporon.