2-Aminoacetophenone as a potential breath biomarker for Pseudomonas aeruginosa in the cystic fibrosis lung.

Amy J Scott-Thomas,Richard Laing,Michael Epton,Philip K Pattemore,John Pearson,Stephen T Chambers,Mona Syhre

doi:10.1186/1471-2466-10-56

Abstract

BackgroundPseudomonas aeruginosa infections are associated with progressive life threatening decline of lung function in cystic fibrosis sufferers. Growth of Ps. aeruginosa releases a "grape-like" odour that has been identified as the microbial volatile organic compound 2-aminoacetophenone (2-AA).MethodsWe investigated 2-AA for its specificity to Ps. aeruginosa and its suitability as a potential breath biomarker of colonisation or infection by Solid Phase Micro Extraction and Gas Chromatography-Mass Spectrometry (GC/MS).ResultsCultures of 20 clinical strains of Ps. aeruginosa but not other respiratory pathogens had high concentrations of 2-AA in the head space of in vitro cultures when analysed by GC/MS. 2-AA was stable for 6 hours in deactivated glass sampling bulbs but was not stable in Tedlar® bags. Optimisation of GC/MS allowed detection levels of 2-AA to low pico mol/mol range in breath. The 2-AA was detected in a significantly higher proportion of subjects colonised with Ps. aeruginosa 15/16 (93.7%) than both the healthy controls 5/17 (29%) (p < 0.0002) and CF patients not colonised with Ps. aeruginosa 4/13(30.7%) (p < 0.001). The sensitivity and specificity of the 2-AA breath test compared to isolation of Ps. aeruginosa in sputum and/or BALF was 93.8% (95% CI, 67-99) and 69.2% (95% CI, 38-89) respectively. The peak integration values for 2-AA analysis in the breath samples were significantly higher in Ps. aeruginosa colonised subjects (median 242, range 0-1243) than the healthy controls (median 0, range 0-161; p < 0.001) and CF subjects not colonised with Ps. aeruginosa (median 0, range 0-287; p < 0.003)ConclusionsOur results report 2-AA as a promising breath biomarker for the detection of Ps. aeruginosa infections in the cystic fibrosis lung.

Highlights

Pseudomonas aeruginosa infections are associated with progressive life threatening decline of lung function in cystic fibrosis sufferers
Many other bacterial species persist and grow in the Cystic Fibrosis (CF) lung, chronic Ps. aeruginosa infection correlates with declining lung function and high mortality rates [4,9]
Detection of 2-AA in breath samples The 2-AA was detected in a significantly higher proportion of subjects colonised with Ps. aeruginosa 15/16 (93.7%) than both the healthy controls 5/17 (29%) (p < 0.0002) and CF patients not colonised with Ps. aeruginosa 4/13 (30.7%) (p < 0.001)

Summary

Introduction

Pseudomonas aeruginosa infections are associated with progressive life threatening decline of lung function in cystic fibrosis sufferers. Growth of Ps. aeruginosa releases a “grape-like” odour that has been identified as the microbial volatile organic compound 2-aminoacetophenone (2-AA). Pseudomonas aeruginosa is a Gram negative bacterium that produces a sweet “grape-like” odour during growth. Cox & Parker [2] confirmed 2-AA as the compound responsible for this odour and we have successfully detected and identified 2-AA in the headspace of in vitro cultures using gas chromatography/. The secretion of hyperviscous mucus in the CF-affected lung provides Ps. aeruginosa with a nutritionally rich growth environment, where it often grows to high cell densities (>109 cells/ml sputum) [7,8]. Many other bacterial species persist and grow in the CF lung, chronic Ps. aeruginosa infection correlates with declining lung function and high mortality rates [4,9]

Methods

Results

Conclusion