Bacterial cyanogenesis occurs in the cystic fibrosis lung

¹ Respiratory Research Group, Menzies Research Institute, University of Tasmania, Collins Street, Hobart, Tasmania

^* To whom correspondence should be addressed. E-mail: d.e.c.reid{at}utas.edu.au.

	Abstract

The cystic fibrosis lung environment is poorly defined, but data suggest that bacteria may encounter reduced oxygen tensions and possibly a frankly anaerobic environment. Pseudomonas aeruginosa produces the potent toxin cyanide under strictly micro-aerobic conditions. We looked for evidence of bacterial cyanogenesis in the CF lung by measuring sputum cyanide concentrations.

Sputum cyanide was measured in seven stable CF patients and before and after intravenous antibiotic therapy during a hospital admission in a further eight patients experiencing acute exacerbations. All patients were chronically infected with P. aeruginosa. Comparative sputum data were obtained from nine CF patients with no documented P. aeruginosa infection and 10 healthy, non-smoking normal volunteers.

High levels of cyanide were detected in all of the P. aeruginosa infected stable CF patients (median 0.56 µg·ml^-1, range 0.37–2.81 µg·ml^-1), and in 7/8 acute sputum samples (median 0.73 µg·ml^-1, range 0–1.43 µg·ml^-1). In contrast, cyanide was not detectable in sputum from 8/9 CF patients without P. aeruginosa infection or in any of the normal controls. Intravenous antibiotic treatment significantly reduced sputum cyanide levels (median 0.73 µg·ml^-1 to median 0.0 µg·ml^-1, p=0.05).

The cyanide detected indicates that the CF lung provides a predominantly micro-aerobic environment for P. aeruginosa. Cyanide is likely to be a potentially important virulence factor in P. aeruginosa infected CF patients.