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1.
Microbial volatiles as diagnostic biomarkers of bacterial lung infection in mechanically ventilated patients
Waqar M Ahmed, Dominic Fenn, Iain R. White, Breanna Dixon, Tamara M E Nijsen, Hugo H Knobel, Paul Brinkman, Pouline M P van Oort, Marcus J Schultz, Paul Dark, Royston Goodacre, Timothy Felton, Lieuwe D J Bos, Stephen J. Fowler, 2022, original scientific article

Abstract: Background Early and accurate recognition of respiratory pathogens is crucial to prevent increased risk of mortality in critically ill patients. Microbial-derived volatile organic compounds (mVOCs) in exhaled breath could be used as non-invasive biomarkers of infection to support clinical diagnosis. Methods In this study, we investigated the diagnostic potential of in vitro confirmed mVOCs in the exhaled breath of patients under mechanically ventilation from the BreathDx study. Samples were analysed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Results Pathogens from bronchoalveolar lavage (BAL) cultures were identified in 45/89 patients and S. aureus was the most commonly identified pathogen (n = 15). Out of 19 mVOCs detected in the in vitro culture headspace of four common respiratory pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli), 14 were found in exhaled breath samples. Higher concentrations of two mVOCs were found in the exhaled breath of patients infected with S. aureus compared to those without (3-methylbutanal p < 0.01. AUROC = 0.81-0.87 and 3-methylbutanoic acid p = 0.01. AUROC = 0.79-0.80). In addition, bacteria identified from BAL cultures which are known to metabolise tryptophan (Escherichia coli, Klebsiella oxytoca and Haemophilus influenzae) were grouped and found to produce higher concentrations of indole compared to breath samples with culture-negative (p = 0.034) and other pathogen-positive (p = 0.049) samples. Conclusions This study demonstrates the capability of using mVOCs to detect the presence of specific pathogen groups with potential to support clinical diagnosis. Although not all mVOCs were found in patient samples within this small pilot study, further targeted and qualitative investigation is warranted using multi-centre clinical studies.
Keywords: Breath, VOCs, infection, respiratory pathogens, VAP
Published in RUNG: 28.11.2022; Views: 1557; Downloads: 0
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2.
Breath and plasma metabolomics to assess inflammation in acute stroke
Waqar Ahmed, Iain R. White, Maxim Wilkinson, Craig Johnson, Nicholas J. W. Rattray, Amit K. Kishore, Royston Goodacre, Craig J. Smith, Stephen J. Fowler, 2021, original scientific article

Abstract: Inflammation is strongly implicated in both injury and repair processes occurring after stroke. In this exploratory study we assessed the feasibility of repeated sampling of exhaled volatile organic compounds and performed an untargeted metabolomic analysis of plasma collected at multiple time periods after stroke. Metabolic profiles were compared with the time course of the inflammatory markers C-reactive protein (CRP) and interleukin-6 (IL-6). Serial breath sampling was well-tolerated by all patients and the measurement appears feasible in this group. We found that exhaled decanal tracks CRP and IL-6 levels post-stroke and correlates with several metabolic pathways associated with a post-stroke inflammatory response. This suggests that measurement of breath and blood metabolites could facilitate development of novel therapeutic and diagnostic strategies. Results are discussed in relation to the utility of breath analysis in stroke care, such as in monitoring recovery and complications including stroke associated infection.
Keywords: stroke, metabolomics, breath, VOCs, inflammation
Published in RUNG: 18.11.2021; Views: 1930; Downloads: 62
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3.
Detection and quantification of exhaled volatile organic compounds in mechanically ventilated patients–comparison of two sampling methods
Iain R. White, Pouline M. van Oort, Waqar Ahmed, Craig Johnson, Jonathan Bannard-Smith, Timothy Felton, Lieuwe D. Bos, Royston Goodacre, Paul Dark, Stephen J. Fowler, 2020, original scientific article

Abstract: Exhaled breath analysis is a promising new diagnostic tool, but currently no standardised method for sampling is available in mechanically ventilated patients. We compared two breath sampling methods, first using an artificial ventilator circuit, then in “real life” in mechanically ventilated patients on the intensive care unit. In the laboratory circuit, a 24-component synthetic-breath volatile organic compound (VOC) mixture was injected into the system as air was sampled: (A) through a port on the exhalation limb of the circuit and (B) through a closed endo-bronchial suction catheter. Sorbent tubes were used to collect samples for analysis by thermal desorption-gas chromatography-mass spectrometry. Realistic mechanical ventilation rates and breath pressure–volume loops were established and method detection limits (MDLs) were calculated for all VOCs. Higher yields of VOCs were retrieved using the closed suction catheter; however, for several VOCs MDLs were compromised due to the background signal associated with plastic and rubber components in the catheters. Different brands of suction catheter were compared. Exhaled VOC data from 40 patient samples collected at two sites were then used to calculate the proportion of data analysed above the MDL. The relative performance of the two methods differed depending on the VOC under study and both methods showed sensitivity towards different exhaled VOCs. Furthermore, method performance differed depending on recruitment site, as the centres were equipped with different brands of respiratory equipment, an important consideration for the design of multicentre studies investigating exhaled VOCs in mechanically ventilated patients.
Keywords: Volatile organic compounds, infection, breath, ventilator associated pneumonia
Published in RUNG: 10.12.2020; Views: 2820; Downloads: 0
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4.
Metabolic dysregulation in vitamin E and carnitine shuttle energy mechanisms associate with human frailty
Nicholas Rattray, Drupad Trivedi, Yun Xu, Tarani Chandola, Caroline Johnson, Alan Marshall, Krisztina Mekli, Zahra Rattray, Gindo Tampubolon, Bram Vanhoutte, Iain R. White, Frederick Wu, Neil Pendleton, James Nazroo, Royston Goodacre, 2019, original scientific article

Abstract: Global ageing poses a substantial economic burden on health and social care costs. Enabling a greater proportion of older people to stay healthy for longer is key to the future sustainability of health, social and economic policy. Frailty and associated decrease in resilience plays a central role in poor health in later life. In this study, we present a population level assessment of the metabolic phenotype associated with frailty. Analysis of serum from 1191 older individuals (aged between 56 and 84 years old) and subsequent longitudinal validation (on 786 subjects) was carried out using liquid and gas chromatography-mass spectrometry metabolomics and stratified across a frailty index designed to quantitatively summarize vulnerability. Through multivariate regression and network modelling and mROC modeling we identified 12 significant metabolites (including three tocotrienols and six carnitines) that differentiate frail and non-frail phenotypes. Our study provides evidence that the dysregulation of carnitine shuttle and vitamin E pathways play a role in the risk of frailty.
Keywords: metabolomics, frailty, ageing, LC-MS, serum
Published in RUNG: 08.11.2019; Views: 3539; Downloads: 90
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5.
Circadian rhythm of exhaled biomarkers in health and asthma
Max Wilkinson, Robert Maidstone, Andrew Loudon, John Blaikley, Iain R. White, Dave Singh, David Ray, Royston Goodacre, Stephen Fowler, Hannah Durrington, 2019, original scientific article

Abstract: Circadian rhythms control many biological processes in the body in both health and disease. Greater understanding of diurnal variability in disease related biomarkers is crucial for their application in clinical practice and biomarkers of circadian rhythm are required to facilitate further research into disturbed chronicity. To determine if fractional exhaled nitric oxide and breath volatile biomarkers vary rhythmically during the day in healthy and asthmatic individuals. Ten individuals with moderate, atopic asthma (on regular inhaled corticosteroids) and 10 healthy volunteers (all non-smokers) completed an overnight visit where their exhaled breath volatiles and forced exhaled nitric oxide levels were collected every 6 h. Breath volatiles were analysed using gas chromatography mass spectrometry, after trapping these volatiles on sorbent materials for thermal desorption. Nine breath volatiles (including acetone and isoprene) exhibit diurnal variation across all individuals. Furthermore the circadian pattern of several VOCs is altered in individuals with asthma and fractional exhaled nitric oxide is rhythmic in asthma but not in healthy controls. Markers of circadian rhythm can be identified in breath and may offer insight into circadian profiling to help treat disease. Additionally this work suggests that time of day must be controlled when designing future biomarker discovery studies. Further work is required with larger cohorts to validate and extend these findings.
Keywords: VOCs, breath, asthma, circadian
Published in RUNG: 21.10.2019; Views: 3590; Downloads: 0
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6.
Development of an adaptable headspace sampling method for metabolic profiling of the fungal volatome
Waqar M Ahmed, Pavlos Geranios, Iain R. White, Oluwasola Lawal, Tamara M Nijsen, Michael J Bromley, Royston Goodacre, Nicholas D Read, Stephen J. Fowler, 2018, original scientific article

Abstract: Pulmonary aspergillosis can cause serious complications in people with a suppressed immune system. Volatile metabolites emitted by Aspergillus spp. have shown promise for early detection of pathogenicity. However, volatile profiles require further research, as effective headspace analysis methods are required for extended chemical coverage of the volatome; in terms of both very volatile and semi-volatile compounds. In this study, we describe a novel adaptable sampling method in which fungal headspace samples can be sampled continuously throughout a defined time period using both active (pumped) and passive (diffusive) methods, with the capability for samples to be stored for later off-line analysis. For this method we utilise thermal desorption-gas chromatography-mass spectrometry to generate volatile metabolic profiles using Aspergillus fumigatus as the model organism. Several known fungal-specific volatiles associated with secondary metabolite biosynthesis (including α-pinene, camphene, limonene, and several sesquiterpenes) were identified. A comparison between the wild-type A. fumigatus with a phosphopantetheinyl transferase null mutant strain (ΔpptA) that is compromised in secondary metabolite synthesis, revealed reduced production of sesquiterpenes. We also showed the lack of terpene compounds production during the early growth phase, whilst pyrazines were identified in both early and late growth phases. We have demonstrated that the fungal volatome is dynamic and it is therefore critically necessary to sample the headspace across several time periods using a combination of active and passive sampling techniques to analyse and understand this dynamism.
Keywords: Volatile Organic Compounds, Fungi, Mycelial growth
Published in RUNG: 18.07.2019; Views: 3188; Downloads: 0
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7.
TD/GC–MS analysis of volatile markers emitted from mono- and co-cultures of Enterobacter cloacae and Pseudomonas aeruginosa in artificial sputum
Iain R. White, Oluwasola Lawal, Hugo Knobel, Weda Hans, Tamara M E Nijsen, Royston Goodacre, Stephen J. Fowler, Waqar M Ahmed, Antonio Artigas, Jonathan Barnard-Smith, Lieuwe D Bos, Marta Camprubi, Luis Coelho, Paul Dark, Alan Davie, Emili Diaz, Gemma Goma, Timothy Felton, Jan H Leopold, Pouline M P van Oort, Pedro Póvoa, Craig Portsmouth, 2018, original scientific article

Abstract: Introduction: Infections such as ventilator-associated pneumonia (VAP) can be caused by one or more pathogens. Current methods for identifying these pathogenic microbes often require invasive sampling, and can be time consuming, due to the requirement for prolonged cultural enrichment along with selective and differential plating steps. This results in delays in diagnosis which in such critically ill patients can have potentially life-threatening consequences. Therefore, a non-invasive and timely diagnostic method is required. Detection of microbial volatile organic compounds (VOCs) in exhaled breath is proposed as an alternative method for identifying these pathogens and may distinguish between mono- and poly-microbial infections. Objectives: To investigate volatile metabolites that discriminate between bacterial mono- and co-cultures. Methods: VAP-associated pathogens Enterobacter cloacae and Pseudomonas aeruginosa were cultured individually and together in artificial sputum medium for 24 h and their headspace was analysed for potential discriminatory VOCs by thermal desorption gas chromatography–mass spectrometry. Results: Of the 70 VOCs putatively identified, 23 were found to significantly increase during bacterial culture (i.e. likely to be released during metabolism) and 13 decreased (i.e. likely consumed during metabolism). The other VOCs showed no transformation (similar concentrations observed as in the medium). Bacteria-specific VOCs including 2-methyl-1-propanol, 2-phenylethanol, and 3-methyl-1-butanol were observed in the headspace of axenic cultures of E. cloacae, and methyl 2-ethylhexanoate in the headspace of P. aeruginosa cultures which is novel to this investigation. Previously reported VOCs 1-undecene and pyrrole were also detected. The metabolites 2-methylbutyl acetate and methyl 2-methylbutyrate, which are reported to exhibit antimicrobial activity, were elevated in co-culture only. Conclusion: The observed VOCs were able to differentiate axenic and co-cultures. Validation of these markers in exhaled breath specimens could prove useful for timely pathogen identification and infection type diagnosis.
Keywords: Bacteria, Enterobacter cloacae, Gas Chromatography-Mass Spectrometry, Infection, Pseudomonas aeruginosa, Volatile organic compounds
Published in RUNG: 18.07.2019; Views: 4802; Downloads: 114
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