Profiling of Volatile Metabolites of Escherichia coli Using Gas Chromatography-Mass Spectrometry

Current diagnostic methods for bacterial infections in critically ill patients, including ventilator-associated pneumonia (VAP), are time-consuming, while empirical antibiotic therapy contributes to rising resistance. Bacteria-derived volatile organic compounds (VOCs) are being explored as specific biomarkers for pathogen identification and treatment monitoring. This study expands knowledge of Escherichia coli metabolism by identifying VOCs produced by both multidrug-resistant and susceptible strains, characterizing their temporal profiles during growth, and assessing VOC profile changes after imipenem exposure. Reference strains and 21 clinical isolates (derived from BAL samples of VAP patients) were cultured under controlled conditions. Headspace VOCs were preconcentrated using multibed sorption tubes and analyzed by gas chromatography-mass spectrometry (GC-MS), with compound identities confirmed using external standards. Sampling at seven time points over 24 h cultures revealed three VOC emission patterns: continuous release, temporary maximum, and compound uptake. In total, 57 VOCs were identified from the susceptible strain and 41 from the resistant one, with dimethyl disulfide, 2-butenal, ethyl acetate, and furan elevated in the resistant strain. Imipenem addition altered VOC production in the susceptible strain, with levels of six compounds elevated and seven reduced, while resistant profiles remained stable. Clinical isolates produced 71 VOCs, showing greater metabolic diversity and highlighting the relevance of isolate-derived VOCs in future studies.