Abstract
BackgroundThe gaseous headspace above naïve Escherichia Coli (E. coli) cultures and whole human blood inoculated with E. coli were collected and analyzed for the presence of trace gases that may have the potential to be used as novel, non-invasive markers of infectious disease.MethodsThe naïve E. coli culture, LB broth, and human whole blood or E. coli inoculated whole blood were incubated in hermetically sealable glass bioreactors at 37°C for 24 hrs. LB broth and whole human blood were used as controls for background volatile organic compounds (VOCs). The headspace gases were collected after incubation and analyzed using a gas chromatographic system with multiple column/detector combinations.ResultsSix VOCs were observed to be produced by E. coli-infected whole blood while there existed nearly zero to relatively negligible amounts of these gases in the whole blood alone, LB broth, or E. coli-inoculated LB broth. These VOCs included dimethyl sulfide (DMS), carbon disulfide (CS2), ethanol, acetaldehyde, methyl butanoate, and an unidentified gas S. In contrast, there were several VOCs significantly elevated in the headspace above the E. coli in LB broth, but not present in the E. coli/blood mixture. These VOCs included dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), methyl propanoate, 1-propanol, methylcyclohexane, and unidentified gases R2 and Q.ConclusionsThis study demonstrates 1) that cultivated E. coli in LB broth produce distinct gas profiles, 2) for the first time, the ability to modify E. coli-specific gas profiles by the addition of whole human blood, and 3) that E. coli-human whole blood interactions present different gas emission profiles that have the potential to be used as non-invasive volatile biomarkers of E. coli infection.
Highlights
The gaseous headspace above naïve Escherichia Coli (E. coli) cultures and whole human blood inoculated with E. coli were collected and analyzed for the presence of trace gases that may have the potential to be used as novel, non-invasive markers of infectious disease
After statistical analysis, 40 gases were allocated into five categories based on the pattern of gas release: category 1: volatile organic compounds (VOCs) elevated from E. coli-inoculated human whole blood,; category 2: VOCs elevated from E. coli in LB broth; category 3: VOCs elevated from naïve E. coli in broth, but decreased by E. coli-inoculated whole blood; category 4: VOCs mainly from pure LB broth only; category 5: VOCs mainly from human whole blood only
This study demonstrates 1) that cultivated E. coli in LB broth produces distinct gas profiles, 2) for the first time the ability to modify E. coli-specific gas profiles by the addition of whole human blood (i.e., Methyl Propanoate was highly emitted from E. coli in LB broth, but barely detected in human whole blood), and 3) of most significance, that the data suggests that E. coli-human whole blood interaction has different gas emission profiles that can be used as non-invasive markers of E. coli infection
Summary
The gaseous headspace above naïve Escherichia Coli (E. coli) cultures and whole human blood inoculated with E. coli were collected and analyzed for the presence of trace gases that may have the potential to be used as novel, non-invasive markers of infectious disease. The interest in using exhaled gases as non-invasive biomarkers in clinical diagnostics and therapeutic monitoring has steadily increased [1]. Identifying and quantifying gases in the exhaled human breath provide a non-invasive means of obtaining information about host responses to infection. It is conceivable that the host immune response may yield gases unique to one pathogen or another. Escherichia Coli (E. coli) was used as a model infectious organism to 1) determine the unique gas profile of bacteria in a “naïve” state and 2) investigate the VOCs that result from the bacteria and whole blood interactions. VOC profiles found in the interaction of bacteria and immune cells containing whole blood may provide a beginning interpretation of the exhaled breath gases from infected subjects
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