Abstract
Hydrogen cyanide (HCN) has been recognized as a potential biomarker for non-invasive diagnosis of Pseudomonas aeruginosa infection in the lung. However, the oral cavity is a dominant production site for exhaled HCN and this contribution can mask the HCN generated in the lung. It is thus important to understand the sources of HCN production in the oral cavity. By screening of oral anaerobes for HCN production, we observed that the genus of Porphyromonas, Prevotella and Fusobacterium generated low levels of HCN in vitro. This is the first study to show that oral anaerobes are capable of producing HCN in vitro. Further investigations were conducted on the species of P. gingivalis and we successfully detected HCN production (0.9–10.9 ppb) in the headspace of three P. gingivalis reference strains (ATCC 33277, W50 and OMG 434) and one clinical isolate. From P. gingivalis ATCC 33277 and W50, a strong correlation between HCN and CO2 concentrations (rs = 0.89, p < 0.001) was observed, indicating that the HCN production of P. gingivalis might be connected with the bacterial metabolic activity. These results indicate that our setup could be widely applied to the screening of in vitro HCN production by both aerobic and anaerobic bacteria.
Highlights
Other sources contribute to the observed mouth-exhaled Hydrogen cyanide (HCN) levels
E. coli American Type Culture Collection (ATCC) 25922 and P. aeruginosa ATCC BAA47 were used as a negative and positive control, respectively, to show that our proposed system is valid for the determination of HCN from the headspace of bacterial cultures
HCN was not detected in the headspace of E. coli ATCC 25922 after 24 hours of culturing
Summary
Other sources contribute to the observed mouth-exhaled HCN levels. In adult P. aeruginosa infected patients, the concentrations of mouth-exhaled HCN (7.5–29 ppb) were not significantly elevated compared to healthy subjects (2.3–20 ppb)[15]. Studies in healthy volunteers have shown that mouth-exhaled HCN levels are in general higher than nose-exhaled levels[16,17]. These findings indicate that there are significant sources of HCN within the oral cavity. We have shown in a previous study that mouth-exhaled HCN levels decrease after a disinfectant mouth rinse[18] These facts imply that a significant part of the mouth-exhaled HCN might be generated by oral bacteria. We screened four species of oral anaerobes for the production of HCN and conducted further investigations on four different strains of P. gingivalis These in vitro measurements are the first steps towards elucidating the source of orally generated HCN
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