The DOI matches its Crossref record; 31 of the 31 references it cites were found in a registry or an index.
A Rapid and Specific Method for the Detection of Indole in Complex Biological Samples
Open accessAbstract
Indole, a bacterial product of tryptophan degradation, has a variety of important applications in the pharmaceutical industry and is a biomarker in biological and clinical specimens. Yet, specific assays to quantitate indole are complex and require expensive equipment and a high level of training. Thus, indole in biological samples is often estimated using the simple and rapid Kovács assay, which nonspecifically detects a variety of commonly occurring indole analogs. We demonstrate here a sensitive, specific, and rapid method for measuring indole in complex biological samples using a specific reaction between unsubstituted indole and hydroxylamine. We compared the hydroxylamine-based indole assay (HIA) to the Kovács assay and confirmed that the two assays are capable of detecting microgram amounts of indole. However, the HIA is specific to indole and does not detect other naturally occurring indole analogs. We further demonstrated the utility of the HIA in measuring indole levels in clinically relevant biological materials, such as fecal samples and bacterial cultures. Mean and median fecal indole concentrations from 53 healthy adults were 2.59 mM and 2.73 mM, respectively, but varied widely (0.30 mM to 6.64 mM) among individuals. We also determined that enterotoxigenic Escherichia coli strain H10407 produces 3.3 ± 0.22 mM indole during a 24-h period in the presence of 5 mM tryptophan. The sensitive and specific HIA should be of value in a variety of settings, such as the evaluation of various clinical samples and the study of indole-producing bacterial species in the gut microbiota.
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“In human feces, indole is detectable at micromolar concentrations (Darkoh et al., 2015)”
From The Microbiota-Gut-Brain Axis (2019) · cites this paper as Darkoh et al., 2015
Citations
Cites
Metabolomics analysis reveals large effects of gut microflora on mammalian blood metabolites
Wikoff, W. R., Anfora, A. T., Liu, J., Schultz, P. G., Lesley, S. A., Peters, E. C., & Siuzdak, G. (2009) · Proceedings of the National Academy of Sciences · doi:10.1073/pnas.0812874106 · Cited by 2,677
Biochemical tests for identification of medical bacteria
MacFaddin, J. F. (1976) · Medical Entomology and Zoology · Cited by 1,442
Indole as an intercellular signal in microbial communities
Lee, J.-H., & Lee, J. (2010) · FEMS Microbiology Reviews · doi:10.1111/j.1574-6976.2009.00204.x · Cited by 1,059
The Infectivity of Cryptosporidium parvum in Healthy Volunteers
DuPont, H. L., Chappell, C. L., Sterling, C. R., Okhuysen, P. C., Rose, J. B., & Jakubowski, W. (1995) · New England Journal of Medicine · doi:10.1056/nejm199503303321304 · Cited by 888
Self-citationBiochemical Tests for Identification of Medical Bacteria
Legolvan, P. C. (1981) · Military Medicine · doi:10.1093/milmed/146.1.60 · Cited by 860
Indole is an inter-species biofilm signal mediated by SdiA
Lee, J., Jayaraman, A., & Wood, T. K. (2007) · BMC Microbiology · doi:10.1186/1471-2180-7-42 · Cited by 471
Virulence of Three DistinctCryptosporidium parvumIsolates for Healthy Adults
Okhuysen, P. C., Chappell, C. L., Crabb, J. H., et al. (1999) · The Journal of Infectious Diseases · doi:10.1086/315033 · Cited by 466
Self-citationSignaling-mediated bacterial persister formation
Vega, N. M., Allison, K. R., Khalil, A. S., & Collins, J. J. (2012) · Nature Chemical Biology · doi:10.1038/nchembio.915 · Cited by 415
Bansal, T., Englert, D. L., Lee, J., Hegde, M., Wood, T. K., & Jayaraman, A. (2007) · Infection and Immunity · doi:10.1128/iai.00630-07 · Cited by 358
Indole induces the expression of multidrug exporter genes in Escherichia coli
Hirakawa, H., Inazumi, Y., Masaki, T., Hirata, T., & Yamaguchi, A. (2005) · Molecular Microbiology · doi:10.1111/j.1365-2958.2004.04449.x · Cited by 328
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Cryan, J. F., O'Riordan, K. J., Cowan, C. S. M., Sandhu, K. V., Bastiaanssen, T. F. S., Boehme, M., Codagnone, M. G., Cussotto, S., Fulling, C., Golubeva, A. V., et al. (2019) · Physiological Reviews · doi:10.1152/physrev.00018.2018 · Cited by 5,286
Gut bacteria selectively promoted by dietary fibers alleviate type 2 diabetes
Zhao, L., Zhang, F., Ding, X., Wu, G., Lam, Y. Y., Wang, X., Fu, H., Xue, X., Lu, C., Ma, J., et al. (2018) · Science · doi:10.1126/science.aao5774 · Cited by 2,304
Microbial tryptophan catabolites in health and disease
Roager, H. M., & Licht, T. R. (2018) · Nature Communications · doi:10.1038/s41467-018-05470-4 · Cited by 2,236
Dual Role of Indoles Derived From Intestinal Microbiota on Human Health
Ye, X., Li, H., Anjum, K., Zhong, X., Miao, S., Zheng, G., Liu, W., & Li, L. (2022) · Frontiers in Immunology · doi:10.3389/fimmu.2022.903526 · Cited by 288
“The Kovács method is the most commonly used to detect the indole concentration in various biological samples (50).”
MethodSinha, A. K., Laursen, M. F., Brinck, J. E., Rybtke, M., Hjørne, A. P., Procházková, N., Pedersen, M., Roager, H. M., & Licht, T. R. (2024) · Nature Microbiology · doi:10.1038/s41564-024-01737-3 · Cited by 313
“Notably, indole is the most abundant tryptophan metabolite detected in mouse caecal contents as well as in human faeces 21,22 .”
Metadata
- Authors
- Darkoh, C., Chappell, C., Gonzales, C., & Okhuysen, P.
- Affiliations
- The University of Texas Health Science Center at Houston (US)
- The University of Texas MD Anderson Cancer Center (US)
- Venue
- Applied and Environmental Microbiology
- Publisher
- American Society for Microbiology
- Published
- 2015-12
- Volume
- 81
- Issue
- 23
- Pages
- 8093-8097
- ISSN
- 0099-2240 (ISSN-L)
- 1098-5336
- PMC
- PMC4651089
- OpenAlex
- W2260701616
- Semantic Scholar
- c738683cc725688e7523668357b4d9797097bcfa
- Cited by
- 156
- References
- 31
- Citations by year
- 2026: 21 · 2025: 19 · 2024: 13 · 2023: 27 · 2022: 18 · 2021: 12 · 2020: 17 · 2019: 12 · 2018: 10 · 2017: 4 · 2016: 2
- FWCI
- 4.41
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Applied and Environmental Microbiology (publishedVersion)
- Europe PMC (PubMed Central) (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Funders
- National Institute of Allergy and Infectious Diseases (R01AI116914)
- National Institute of Diabetes and Digestive and Kidney Diseases (DK56338, P30DK056338)
- Topics
- Health Sciences › Medicine › Microbiology (medical) › Bacterial Identification and Susceptibility Testing
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Polyamine Metabolism and Applications
- Physical Sciences › Chemistry › Analytical Chemistry › Analytical Methods in Pharmaceuticals
- Keywords
- tryptophan degradation, enterotoxigenic Escherichia coli, gut microbiota, biomarkers, bacterial metabolites
- MeSH terms
- Bacteriological Techniques, Environmental Microbiology, Feces, Humans, Indoles, Sensitivity and Specificity, Tryptophan, Hydroxylamine, Enterotoxigenic Escherichia coli
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