Oral Microbiota Alterations and Potential Salivary Biomarkers in Colorectal Cancer: A Next-Generation Sequencing Study.

Alpha diversity indices showed no significant differences in oral microbiota diversity between CRC patients and healthy controls.

• Three alpha diversity indices were tested: Shannon (p = 0.78), Chao1 (p = 0.28), and Simpson (p = 0.81).
• All p-values were well above the significance threshold, indicating similar species richness and evenness between groups.
• The study included 14 CRC patients and 14 healthy controls, with saliva samples collected between March 2023 and December 2023.

Beta diversity analysis revealed significant differences in oral microbial community composition between CRC patients and healthy controls.

• Bray-Curtis principal coordinate analysis (PCoA) showed a statistically significant difference between the two groups (p = 0.003).
• This indicates that while overall diversity metrics were similar, the specific composition of microbial communities differed significantly.
• Analysis was conducted using the Qiime2 (Quantitative Insights Into Microbial Ecology) platform.

The Mycoplasmatota phylum was undetectable in healthy controls but significantly elevated in CRC patients.

• Mean relative abundance of Mycoplasmatota in CRC patients was 0.13 ± 0.30 compared to 0.00 ± 0.00 in controls (p < 0.05).
• This phylum-level difference was identified through OTU distribution analysis.
• The complete absence in healthy controls makes this phylum a distinctive feature of CRC-associated oral microbiota.

Three bacterial species — Metamycoplasma salivarium, Bacteroides intestinalis, and Pseudoprevotella muciniphila — were undetectable in healthy controls but significantly more prevalent in CRC patients.

• All three species showed p < 0.05 when comparing CRC patients to healthy controls.
• None of these species were detectable in the oral microbiota of any healthy control participants.
• These species were identified through OTU distribution analyses using 16S rRNA next-generation sequencing.

LEfSe analysis identified eight bacterial species as potential biomarkers for CRC based on LDA scores greater than 2.

• The eight species identified were: Granulicatella adiacens, Streptococcus thermophilus, Streptococcus gwangjuense, Capnocytophaga sp. FDAARGOS_737, Capnocytophaga gingivalis, Granulicatella elegans, Bacteroides intestinalis, and Pseudoprevotella muciniphila.
• All had Linear Discriminant Analysis (LDA) scores greater than 2, the threshold used to indicate biologically meaningful differences.
• Bacteroides intestinalis and Pseudoprevotella muciniphila appeared in both the OTU distribution analysis and LEfSe analysis, corroborating their potential as biomarkers.

The study was designed as a pilot study investigating the relationship between CRC and oral microbiota using 16S rRNA next-generation sequencing.

• Saliva samples were collected from recently diagnosed CRC patients (n = 14) and healthy controls (n = 14).
• Sample collection occurred between March 2023 and December 2023.
• Phylogenetic analyses included alpha diversity, PCA, PCoA, beta diversity, biomarker, and phenotype analyses conducted on the Qiime2 platform.