(466) Connecting the Genome and Volatiome In Pseudomonas aeruginosa Cystic Fibrosis Lung Infection Isolates

Background: Pseudomonas aeruginosa chronic lung infections in individuals with cystic fibrosis (CF) significantly increase morbidity and mortality [1]. Tracking these infections is critical for monitoring patient health and informing treatments. We are working toward the development of novel breath-based biomarkers to track chronic P. aeruginosa lung infections in situ via its volatile metabolome. P. aeruginosa exhibits a host of virulence factors that allow it to adapt to the CF lung, driven by mutations in major regulatory genes [2,3]. Our research has demonstrated that the disparate phenotypes seen between early and late infection isolates are strongly reflected in the volatile metabolome, suggesting that volatile organic compounds (VOCs) could be used as biomarkers of phenotypes to stage and track infections [4]. Connecting these volatilome trends to the underlying genetic mechanisms that drive these phenotypes is an important step in this pursuit. We hypothesize that these clinically important genetic trends are reflected in the P. aeruginosa volatile metabolome.

Methods: Using comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry, we characterized the volatilomes of P. aeruginosa laboratory strains and isogenic mutants containing loss-of-function mutations in lasR, rhlR, mucA, and pilA. We then employed Random Forest models to identify VOCs that are discriminative for wild-type and mutant laboratory strains. These VOCs were then tested on CF isolates possessing mutations in the same regulatory genes to validate their translatability and associations with these genotypes.

Results: Random Forest was able to identify both conserved and unique VOCs that accurately discriminate strains with functional and defective lasR, mucA, rhlR, and pilA (Figure). Many of these VOCs were produced in significantly different relative abundances.

Conclusions: These results suggest that P. aeruginosa strains are capable of producing unique and conserved VOCs that are strongly associated with mutations in specific genes and, to our knowledge, this is the first attempt to translate the P. aeruginosa genome to the volatilome. This is an important step in identifying volatile metabolites that have prognostic utility

Acknowledgements: This work was supported by the Cystic Fibrosis Foundation and the National Institutes of Health. Laboratory reference strains were provided by D. Hogan, B.S. Tseng, and M. Wargo. Clinical isolates were obtained from the Cystic Fibrosis Isolate Core at Seattle Children’s Center for Global Infectious Disease Research, funded by the National Institutes of Health (P30 DK089507) and the Cystic Fibrosis Foundation (HOFFMA20Y2-OUT).

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