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 (p=0.003), 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 (p=0.051).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.

Aims In cystic fibrosis, Pseudomonas aeruginosa (PA) infection is associated with significant morbidity and mortality. Unfortunately, inpatients who cannot expectorate sputum current diagnostic methods are unreliable, unpleasant or invasive. This has lead to increased interest in using the cyanogenic properties of PA to develop a non-microbiological method for its detection. Prior to this development it needs to be determined if cyanide production varies according to PA strain. Methods The hydrogen cyanide (HCN) released into the gas phase by 96 genotyped PA 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-PA cultures and incubated blank agar plates was also measured. Results The 96 samples included 26 different strains; four were previously described epidemic strains (Liverpool, Midlands1, Midlands2 and Stoke). Extremely low levels of HCN (<10 parts per billion) were produced by the control samples. All the PA strains produced more HCN than the controls. Across all four time points the non-mucoid samples produced more HCN than the mucoid samples (p=0.003), they also produced more HCN after 24 h when the time points were analysed separately (p=0.008). When samples were separated according to strain and phenotype, some strains (Liverpool and Stoke) continued to show higher HCN production by non-mucoid samples but others (Midlands1) showed higher production by mucoid samples. Clear differences were apparent in the HCN production between the different strains. Multivariant analysis of the three commonest strains (Liverpool, Midlands1 and Stoke) revealed a significant effect of strain (p<0.001) and a borderline interaction of strain and phenotype (p=0.051). Discussion This supports previous studies showing PA is one of a limited number of organisms to produce cyanide and SIFT-MS is a sensitive and reproducible way of analysing this. It is the first study to demonstrate that cyanide production is dependent on the PA strain and that the effect of phenotype may vary between strains. As all the PA strains produced more HCN than the controls, it creates further interest in using the cyanogenic properties of PA to develop a diagnostic test.

Introduction Although it is well reported in adults, there is relatively little data on how children with asthma and their parents describe their attitudes to the disease, expectations of therapy and perception of treatment benefit. Our aim was to investigate this and determine if they differed from reports by adults with asthma. We plan to use the results to refine patient reported outcome measures for children with asthma. Methods We recruited families with an asthmatic child (4–11 years) who had recently been prescribed a change in treatment (starting inhaled corticosteroid monotherapy (ICS) or changing from ICS to inhaled corticosteroid/long acting ß2 agonist combination therapy (ICS/LABA). Semi-structured interviews were conducted with the parents and the children if aged 7–11 years. Transcripts were analysed using a combination of thematic and content analysis and recruitment discontinued in each group once data saturation was reached. Results We undertook 41 interviews including 28 parents and 13 children. The numbers in each group can be seen in Abstract P79 table 1. All the children on ICS/LABA had been changed as their symptoms were not controlled on ICS monotherapy. The interviews highlighted the significant effects that paediatric asthma has on the whole family and the distress the symptoms cause to the child and their parents. Exacerbations led to frequent school absence and associated time off work for the parents. Both parents and children hoped that the new medication would lead to better symptom control, increased participation in physical activities and decreased visits to the GP or hospital. Positive effects of treatment change were identified, particularly in those changing from ICS to ICS/LABA. Benefits described included improvement in symptoms (especially cough and wheeze), increased participation in sport or play activities and reduced rescue medication use. These effects resulted in few visits to the GP/hospital and better attendance at school. Conclusions While asthma symptoms prevent adults and children from participating in different types of activities (eg, school not employment), children and their parents report the same concepts as adult patients with asthma.

157 Variation in canide production between different strains of Pseudomonas aeruginosa F.J. Gilchrist1,2, A. Alcock3, J. Belcher4, M. Brady2, A. Jones5, S. David6, S. Patrik6, K. Webb5, W. Lenney2. 1Manchester Adult CF Centre, Mancehster, United Kingdom; 2University of Hospital of North Staffordshire, Academic Department of Child Health, Stoke on Trent, United Kingdom; 3University Hospital of North Staffordshire, Microbiology, Stoke on Trent, United Kingdom; 4Keele University, Institute for Primary Care and Health Sciences Research, Keele, United Kingdom; 5Manchester Adult CF Centre, Manchester, United Kingdom; 6Keele University, Institute of Science and Technology in Medicine, Keele, United Kingdom

Using selected ion flow tube mass spectrometry (SIFT-MS), measurements have been made of the levels of several metabolites in the exhaled breath of 200 healthy school children. Thus, concentration distributions of each metabolite have been obtained for the first time in the paediatric age range. The median values (in parentheses) of the concentrations in parts per billion, ppb, were ammonia (628), acetone (297), methanol (193), ethanol (187), isoprene (37), propanol (16), acetaldehyde (23) and pentanol (15). Hydrogen cyanide was not present in the breath above the detection limit of 2 ppb in the majority of subjects. The water vapour level (humidity) of the breath samples was routinely measured as a check on the sample integrity. Such data are essential if SIFT-MS breath analyses are to be used as a clinical tool to aid diagnosis and/or as a monitor of disease in children. The levels of metabolites usually followed a log-normal distribution and the levels of some compounds were similar to those obtained previously in adults. Lower values were found in the levels of acetone, ammonia, methanol and isoprene. There were no major variations in relation to gender. Some metabolites showed significant variation in relation to age and body mass index. To our knowledge, these are the first measurements of exhaled mouth breath pentanol levels. The median ammonia levels in mouth-exhaled breath of these children decreased with age, whereas in older adults, ammonia has been shown to increase with age. Breath acetone levels were significantly increased for those who had not eaten for more than 6 h prior to providing the breath sample, although dietary control was not a mandatory aspect of the protocol.