Biofilm Formation by Mycobacterium abscessus in a Lung Cavity

A 55-year-old man with chronic obstructive pulmonary disease and Mycobacterium abscessus lung infection was treated with intravenous and oral antimycobacterial drugs for 4 months. He was then referred for adjunctive surgical resection of a right upper lobe cavity (Figure 1). The surgical pathology revealed numerous acid-fast bacilli lining the central surface of the cavity (Figure 2); M. abscessus grew in culture within 3 days. His symptoms and radiographs improved postoperatively, and all sputa specimens over the subsequent 10 months were culture negative. M. abscessus can form biofilm in vitro (1) and has recently been reported to form biofilm in vivo within thickened alveolar walls and airways of patients with cystic fibrosis (2). We suspected that these bacteria could form biofilm in lung cavities. Scanning electron microscopy of the cavity wall demonstrated bacilli embedded in a matrix, a typical feature of biofilms, in samples from the lung cavity but not in a remote sample of the lung (Figure 3). There were high levels of total bacteria (3.83 × 107 cfu) in a 0.5-g sample of the lung cavity, of which 7.17 × 105 cfu were in biofilm, determined by an assay using brief exposure to dilute bleach solution, as previously described (3). The bacterial composition of the cavity was dominated by Mycobacterium species as determined by 16S ribosomal RNA sequencing (Figure 4) (4).