Investigation of Volatile Organic Compounds Emitted from Faeces for the Diagnosis of Giardiasis

Abstract

Background: Giardiasis is a common intestinal infection caused by the flagellated intestinal protozoan Giardia duodenalis. Several methods are available for the laboratory diagnosis of Giardia, ranging from the microscopic identification of the parasite trophozoite and cyst stages, to immunodiagnosis and PCR. Giardia has unique metabolic pathways resulting from its lack of mitochondria, making it an ideal target for volatile organic compound (VOC) profiling.
 Aim: To characterise the VOC profile of stool infected with Giardia to detect differences from those found in samples of diarrhoea without Giardia or other infections.
 Method: Stool was obtained from patients with confirmed Giardia infection and controls with diarrhoea but no identifiable infection. Faecal headspace gas extraction and gas chromatography-mass spectrometry were used to extract and identify VOCs.
 Results: More than 100 VOCs were identified when control and Giardia groups were combined, of which 24 showed significant differences between the two groups (p<0.05). Three VOCs had a significantly greater prevalence amongst Giardia cases (p<0.0001) and 9 VOCs showed a significant difference in terms of abundance (p<0.05). AUROC analysis demonstrated a value of 0.902.
 Conclusion: There is a significant difference in the VOC profile of stool from subjects infected with Giardia spp, when compared with non-infected controls. These findings can be explained by the unique metabolism of Giardia.

Volatile organic compounds emitted from faeces as a biomarker for colorectal cancer

“…Using a variety of methods and substrates, other studies have suggested a utility of volatile organic compound analysis for the diagnosis of GI disease, including colorectal cancer. One such study, from 2015, used selected ion flow tube mass spectrometry to analysis volatile organic compounds emitted from faeces of FOBt positive patients.…”

“…The mass spectrometer was run in electron impact (EI) ionisation mode, scanning the mass ion range 10‐300 at 0.05 scan/s. A 4 minute solvent delay was used at the start of the run …”

“…The report generated by AMDIS was further processed by Metab, in order to align metabolites and recalculate their relative abundances based on the intensity of a specific ion mass fragment per metabolite. In order to develop robust parsimonious statistical models, those compounds found to be present in fewer than 20% of the patients in both groups were removed . Compounds were named using IUPAC nomenclature.…”

Vaccination with Bivalent DNA Vaccine of α1-Giardin and CWP2 Delivered by Attenuated Salmonella typhimurium Reduces Trophozoites and Cysts in the Feces of Mice Infected with Giardia lamblia

“…G . lamblia is a parasitic protozoan dwelling in the small intestine of human and mammal animals and causes giardiasis [ 21 ]. Due to the importance of gut-associated lymphoid tissue (GALT) in the immune response to enteric pathogens, a ideal vaccine against gastro-intestinal pathogens should be able to access GALT through mucosal M cells located predominantly in the Peyer’s patches (PP) and therefore activate mucosal defenses in the intestinal tract [ 22 – 24 ].…”

Elevated levels of proinflammatory volatile metabolites in feces of high fat diet fed KK-Ay mice

“…Therefore, fecal VOCs might be a useful group among intestinal metabolites in the regulation of metabolic homeostasis. Interestingly, fecal VOC analysis was performed to evaluate the pathological features of gastrointestinal diseases [18][19][20] including inflammatory bowel disease (IBD) [21][22][23] , irritable bowel syndrome 21,24 , Crohn's disease 25 , colorectal cancer (CRC) 26,27 , and necrotizing enterocolitis 28,29 , as well as infectious diseases including paratuberculosis [30][31][32][33][34] , sepsis 35 , giardiasis 36 , and Clostridium difficile infection 37 . However, it is difficult to handle intestinal microbial VOCs, because of their unpleasant odor, gaseous form, and low boiling point resulting in their loss when using general sample preparation methods including evaporation or concentration.…”