ABSTRACT
In this model study, we explored the host's contribution of breath volatiles to diagnostic secondary electrospray ionisation-mass spectrometry (SESI-MS) breathprints for acute bacterial lung infections, their correlation with the host's immune response, and their use in identifying the lung pathogen. Murine airways were exposed to Pseudomonas aeruginosa and Staphylococcus aureus bacterial cell lysates or to PBS (controls), and their breath and bronchoalveolar lavage fluid (BALF) were collected at six time points (from 6 to 120 h) after exposure. Five to six mice per treatment group and four to six mice per control group were sampled at each time. Breath volatiles were analysed using SESI-MS and the BALF total leukocytes, polymorphonuclear neutrophils, lactate dehydrogenase activity, and cytokine concentrations were quantified. Lysate exposure breathprints contain host volatiles that persist for up to 120 h; are pathogen specific; are unique from breathprints of controls, active infections and cleared infections; and are correlated with the host's immune response. Bacterial lung infections induce changes to the host's breath volatiles that are selective and specific predictors of the source of infection. Harnessing the pathogen-specific volatiles in the host's breath may provide useful information for detecting latent bacterial lung infections and managing the spread of respiratory diseases.
Subject(s)
Lung Diseases/diagnosis , Lung Diseases/immunology , Lung Diseases/microbiology , Volatile Organic Compounds/chemistry , Animals , Bacterial Infections/immunology , Breath Tests , Bronchoalveolar Lavage Fluid/immunology , Cytokines/immunology , Discriminant Analysis , Disease Models, Animal , L-Lactate Dehydrogenase/metabolism , Least-Squares Analysis , Lung/immunology , Male , Mice , Mice, Inbred C57BL , Neutrophils/immunology , Pneumonia, Bacterial/immunology , Pseudomonas Infections/immunology , Pseudomonas aeruginosa , Spectrometry, Mass, Electrospray Ionization , Staphylococcal Infections/immunology , Staphylococcus aureusABSTRACT
Before breath-based diagnostics for lung infections can be implemented in the clinic, it is necessary to understand how the breath volatiles change during the course of infection, and ideally, to identify a core set of breath markers that can be used to diagnose the pathogen at any point during the infection. In the study presented here, we use secondary electrospray ionization-mass spectrometry (SESI-MS) to characterize the breathprint of Pseudomonas aeruginosa and Staphylococcus aureus lung infections in a murine model over a period of 120 h, with a total of 86 mice in the study. Using partial least squares-discriminant analysis (PLS-DA) to evaluate the time-course data, we were able to show that SESI-MS breathprinting can be used to robustly classify acute P. aeruginosa and S. aureus mouse lung infections at any time during the 120 h infection/clearance process. The variable importance plot from PLS indicates that multiple peaks from the SESI-MS breathprints are required for discriminating the bacterial infections. Therefore, by utilizing the entire breathprint rather than single biomarkers, infectious agents can be diagnosed by SESI-MS independent of when during the infection breath is tested.
Subject(s)
Biomarkers/analysis , Pseudomonas Infections/diagnosis , Pseudomonas aeruginosa/isolation & purification , Respiratory Tract Infections/diagnosis , Spectrometry, Mass, Electrospray Ionization/methods , Staphylococcal Infections/diagnosis , Staphylococcus aureus/isolation & purification , Animals , Breath Tests/methods , Disease Models, Animal , Humans , Male , Mice , Mice, Inbred C57BL , Pseudomonas Infections/metabolism , Pseudomonas Infections/microbiology , Respiratory Tract Infections/metabolism , Respiratory Tract Infections/microbiology , Staphylococcal Infections/metabolism , Staphylococcal Infections/microbiologyABSTRACT
Bacterial pneumonia is one of the leading causes of disease-related morbidity and mortality in the world, in part because the diagnostic tools for pneumonia are slow and ineffective. To improve the diagnosis success rates and treatment outcomes for bacterial lung infections, we are exploring the use of secondary electrospray ionization-mass spectrometry (SESI-MS) breath analysis as a rapid, noninvasive method for determining the etiology of lung infections in situ. Using a murine lung infection model, we demonstrate that SESI-MS breathprints can be used to distinguish mice that are infected with one of seven lung pathogens: Haemophilus influenzae, Klebsiella pneumoniae, Legionella pneumophila, Moraxella catarrhalis, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae, representing the primary causes of bacterial pneumonia worldwide. After applying principal components analysis, we observed that with the first three principal components (primarily comprised of data from 14 peaks), all infections were separable via SESI-MS breathprinting (P < 0.0001). Therefore, we have shown the potential of this SESI-MS approach for rapidly detecting and identifying acute bacterial lung infections in situ via breath analysis.
