Since we first recognized the regular presence of gaseous hydrogen cyanide, HCN, in the headspace of plate cultures of the bacterium Pseudomonas aeruginosa, PA, derived from sputum of cystic fibrosis, CF, patients, and following crucial ion chemistry research that allowed accurate quantification of gaseous HCN by selected ion flow tube mass spectrometry, we have carried out many further in vitro and in vivo studies. We have measured HCN in the headspace of various PA culture types, planktonic and biofilm, significant numbers of genetically identified PA strains together with studies of HCN in the mouth-exhaled and nose-exhaled breath of healthy children and adults and those with CF. The major findings are: (i) virtually all strains of PA release HCN when cultured in vitro, as shown by the investigation of more than 150 genetically differentiated strains, both mucoid and non-mucoid. (ii) HCN is present in the mouth-exhaled breath of adults and children, but is at lower concentrations in children. Its concentration is below the detection limit in nose-exhaled breath of healthy people. (iii) HCN is present in both mouth-exhaled and nose-exhaled breath of patients with CF, suggesting the presence of PA in the lower airways as indicated by clinical microbiological cultures. With confirmation of these findings by further research and clinical trials, nose-exhaled breath HCN measurements could be an additional diagnostic tool to detect the early presence of PA in the lower airways and a non-invasive monitor to enhance the likelihood of its eradication.

There is increasing interest in using the cyanogenic properties of Pseudomonas aeruginosa to develop a nonmicrobiological method for its detection. Prior to this, the variation in cyanide production between different P. aeruginosa strains needs to be investigated.Hydrogen cyanide (HCN) released into the gas phase by 96 genotyped P. aeruginosa samples was measured using selected ion flow tube-mass spectrometry after 24, 48, 72 and 96 h of incubation. The HCN produced by a range of non-P. aeruginosa cultures and incubated blank plates was also measured.All P. aeruginosa strains produced more HCN than the control samples, which generated extremely low levels. Analysis across all time-points demonstrated that nonmucoid samples produced more HCN than the mucoid samples (p50.003), but this relationship varied according to strain. There were clear differences in the headspace HCN concentration for different strains. Multivariate analysis of headspace HCN for the commonest strains (Liverpool, Midlands_1 and Stoke-on-Trent, UK) revealed a significant effect of strain (p,0.001) and a borderline interaction of strain and phenotype (p50.051).This evidence confirms that all P. aeruginosa strains produce HCN but to varying degrees and generates interest in the possible future clinical applications of the cyanogenic properties of P. aeruginosa.

Elevated concentrations of hydrogen cyanide (HCN) have been detected in the headspace of Pseudomonas aeruginosa (PA) cultures and in the breath of children with cystic fibrosis (CF) and PA infection. The use of mouth-exhaled breath HCN as a marker of PA infection in adults is more difficult to assess as some without PA infection generate HCN in their mouths. The analysis of breath exhaled via the nose, thereby avoiding volatile compounds produced in the mouth, will demonstrate elevated concentrations of HCN in adult CF patients chronically infected with PA. Using selected ion flow mass spectrometry (SIFT-MS), the mouth and the nose-exhaled breaths of 20 adult CF patients; 10 with chronic PA infection and 10 free from PA infection, were analysed for HCN. Acetone and ethanol were also measured as controls. SIFT-MS allows direct sampling and analysis of single breath exhalations, obviating the need to collect samples into bags or onto traps, which can compromise samples. HCN was detected in the mouth-exhaled breath of patients in both groups and in the nose-exhaled breath of patients with chronic PA infection. The difference in median (IQR) nose-exhaled HCN between the groups is statistically significant (11 (0.8-18) ppbv versus 0 (0-3.2) ppbv, p = 0.03). The concentrations of acetone and ethanol in nose-exhaled and mouth-exhaled breath are in keeping with previous studies. HCN in nose-exhaled breath is a biomarker of chronic airway infection with PA in adults with CF. Its application as a non-invasive diagnostic test for early PA infection warrants further investigation.

During this 9-year study, small but significant declines in health were observed in GH-deficient adults who remained untreated. By contrast, the patients who received GH continuously experienced improvements in energy levels while all other areas of QoL were maintained. The beneficial effects of GH on QoL are therefore maintained with long-term GH replacement and obviate the reduction in QoL seen over time in untreated GH-deficient adults.