Exhaled volatile markers analysed using Selected Ion Flow Tube Mass Spectrometry discriminate Pseudomonas aeruginosa and Streptococcus pneumoniae lung infection in a rat model study

Abstract

Exhaled volatile organic compounds (VOCs) could potentially serve as non-invasive biomarkers for the diagnosis of respiratory infections. This study aims to discriminate rats infected with Pseudomonas aeruginosa (PA) or Streptococcus pneumoniae (SP) from non-infected rats. Exhaled breath was collected from 50 male rats 24h after intra-tracheal inoculation of 200µL saline, or 1x107 colony forming units of SP or PA. VOCs in exhaled breath trapped on sorbent tubes were analysed with Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) after thermal desorption. The pattern of reaction ions with mass/charge ratio 15 to 200 was analysed using sparse partial least squares discriminant analysis. Area under the receiver operating characteristic curve (AUROCC) calculated after leave-one-out cross-validation of the multivariate discriminant analysis was 0.73 (95%CI: 0.57-0.89) for infected vs. non-infected animals. For SP vs. PA the AUROCC was 0.97 (95%CI: 0.93-1) while for SP vs. controls and PA vs. controls it was 0.67 (95%CI: 0.47-0.86) and 0.72 (95%CI: 0.53-0.91), respectively. Exhaled breath analysis discriminated with higher accuracy between animals infected with specific respiratory pathogens compared to infected vs. non-infected animals. Similar findings were observed for VOCs analysed with Gas Chromatography Mass Spectrometry (see submitted ERS abstract from P. M. van Oort et al.). Our results suggest that breath analysis in infected patients may be helpful in discriminating different pathogens. Furthermore, SIFT-MS has potential as a point-of-care tool to assess respiratory infections in clinical practice.