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ORIGINAL RESEARCH ARTICLE

Gut microbiome dysbiosis and colorectal cancer in low- and middle-income countries and the United States: A comparative analysis

Vaishnavi Chilakamarri1 ,  Roshan Paudel1*
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1 Department of Computer Science, School of Computer, Mathematical and Natural Sciences Morgan State University, Baltimore, Maryland , United States of America
MI, 026320095 https://doi.org/10.36922/MI026320095
Received: 4 August 2026 | Revised: 3 October 2026 | Accepted: 12 October 2026 | Published online: 26 October 2026
© 2026 by the Author(3). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

Colorectal cancer (CRC) is a major cause of cancer deaths globally, with rising cases in low- and middle-income countries (LMICs). These trends have been associated with socioeconomic and lifestyle changes accompanying urbanization and dietary Westernization. The gut microbiome has emerged as a key mediator linking environmental factors to CRC. Microbial dysbiosis has been associated with a myriad of downstream carcinogenic effects through metabolic, immune, and inflammatory pathways. However, most existing research on microbiome-related CRC risk focuses on Western populations, creating a gap in comparative characterization of CRC-associated microbiomes in LMIC populations. To fill this gap, the study analyzed publicly available 16S ribosomal RNA (rRNA) sequencing datasets from Sri Lanka, Kenya, and the United States. We performed analyses in R and Python, including taxonomic profiling and alpha- and beta-diversity assessments. The results showed a consistently higher relative abundance of Fusobacteria in CRC than in controls across all populations (8.19% vs 1.64%). Alpha diversity analysis showed slightly higher microbial diversity in controls than in CRC samples, although Wilcoxon tests found no significant within-population differences, while Kruskal–Wallis and Dunn’s tests identified significant population-level differences. Among CRC samples, United States (U.S.) cohorts exhibited the highest median Shannon diversity, followed by Kenya and Sri Lanka. Beta diversity showed substantial overlap among the U.S. cohorts, whereas Sri Lankan and Kenyan samples showed greater dispersion, indicating more variability. However, significant differences in multivariate dispersion (permutational analysis of multivariate dispersion, p = 0.006) indicated that differences in within-group heterogeneity also contributed to the observed separation. These findings highlight substantial microbial variability observed across populations, consistent with environment and lifestyle changes previously reported in transitioning populations. This research addresses a gap in the comparative characterization of CRC-associated microbiomes in underprivileged LMICs and provides a basis for future research evaluating environmental, dietary, and clinical factors.

Graphical abstract
Keywords
Colorectal cancer
Gut microbiome
16S ribosomal RNA
Microbial diversity
Fusobacteria
Low- and middle-income countries
Funding
None.
Conflict of interest
The authors have no conflicts of interest to declare.
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