Introduction Pseudomonas aeruginosa (PA) was thought to be the only organism found in the cystic fibrosis (CF) lung that produced hydrogen cyanide (HCN). A recent study used a cyanide selective electrode to demonstrate HCN production by Burkholderia cepacia complex (BCC) when cultured under biofilm conditions. We replicated this in-vitro experiment using selected ion flow tube mass spectroscopy (SIFT-MS) as a more sensitive method of detecting HCN We also investigated HCN as an in-vivo marker of BCC infection.
Methods Twelve adults with CF were recruited as they had chronic BCC infection and were free from PA infection for >12months. They provided mouth and nose exhalation breaths for HCN analysis and a sputum sample. The sputum sample was cultured and the isolated BCC recultured under planktonic (free floating) and biofilm (non-motile communities attached to glass beads) conditions. The HCN concentration in the headspace of the both culture types was measured after 24, 48, 72 and 96 hours of incubation. Sterile, control cultures were also analysed. Biofilm formation was assessed visually and with spectrophotometry after crystal violet staining. The mouth and nose exhaled breath from 10 patients with CF that were free from PA and BCC infection for >12 months was also analysed.
Results Biofilm formation was confirmed visually and using spectrophotometry: mean(SD) absorbance of crystal violet was 3.43(0.31) absorbance units (AU) in the biofilm cultures compared to 0.005(0.003)AU in the planktonic and control cultures (p<0.001). At each of the 4 time points, the headspace HCN concentration was <10ppbv (equivalent to background levels) for all biofilm, planktonic and control cultures. The mean(SD) breath HCN concentrations were no higher in the subjects with chronic BCC infection than in subjects without BCC infection for mouth exhaled breath (11.0(12.7) v 12.0(12.9) ppbv p=0.87) and nose exhaled breath (0.6(1.1) v 2.1(3.8) p=0.23).
Conclusions Using SIFT-MS we did not identify elevated HCN concentrations in the headspace of BCC cultured under biofilm or planktonic conditions or in the breath of patients with chronic BCC infection. Therefore, HCN does not appear to be an in-vitro or in-vivo marker of BCC infection.