Keele Research Repository

The work presented in this thesis uses Selected Ion Flow Tube Mass Spectrometry to investigate if hydrogen cyanide (HCN) is a marker of Pseudomonas aeruginosa (PA). The initial in-vitro studies measure the HCN released into the gas phase by cultures of PA after various durations of incubation.

Study 1 uses clinical PA isolates with a known genotype and phenotype (mucoid / non-mucoid) and Study 2 uses a selection of the same PA isolates cultured under biofilm and planktonic conditions. Study 4 investigates if HCN is an in-vivo marker of PA infection in children with cystic fibrosis (CF). It is a 2 year observational study of 233 children with CF who are free from PA infection. A breath sample for HCN analysis is collected each time they attend the out-patient clinic. Exhaled breath HCN concentrations are then compared to routine microbiology sample results. The breath samples for this study are collected in sampling bags. In preparation for this, Study 3 identifies the most appropriate bag type as well as the maximum duration of storage and the need for sample warming prior to analysis.

Some healthy adults produce HCN in their oral cavity and therefore mouth-exhaled HCN alone cannot be used as marker of PA infection. Study 5 investigates nose-exhaled HCN as a marker of chronic PA infection in adults with CF. A recent study has shown that Burkholderia Cepacia Complex (BCC) produces cyanide when cultured under biofilm but not planktonic conditions. Study 6 measures the HCN released into the gas phase by in-vitro cultures of BCC as well as HCN concentration in the breath of patients with chronic BCC infection.