Characterisation of the Faecal Microbiota in Dogs with Mast Cell Tumours Compared with Healthy Dogs

Abstract

Mast cell tumours (MCT) are the most common cutaneous neoplasms in dogs, with variable behaviours and patient survival time. Both indolent and aggressive forms have been described, but much remains to be explored regarding prognosis and therapy. Evidence has highlighted the influence of microbiota on multiple health and disease processes, including certain types of cancer in humans. However, knowledge remains scarce regarding microbiota biology and its interactions in both humans and canine cancer patients. This study aimed to characterise the faecal microbiota of dogs with MCT and compare it with that of healthy individuals. Twenty-eight dogs diagnosed with MCT and twenty-eight healthy dogs were enrolled in the study. Faecal samples were collected and analysed by Illumina sequencing of 16S rRNA genes. Alpha diversity was significantly lower in dogs with cancer, and the species diversity InvSimpson Indexwas reduced (p = 0.019). Principal coordinate analysis showed significant differences in the bacterial profile of the two groups: there was a significant lower abundance of the genera Alloprevotella, Holdemanella, Erysipelotrichaceae_UCG-003, and Anaerobiospirillum and, conversely, a significant increase in the genera Escherichia-Shigella and Clostridium sensu stricto 1 in diseased dogs. At the phylum level, Bacteroidota was significantly reduced in diseased dogs (25% in controls vs. 19% in MCT dogs). In conclusion, sequencing analysis provided an overview of the bacterial profile and showed statistical differences in the microbial communities of dogs with MCT compared with healthy dogs, suggesting a link between the gut microbiota and MCT in this species.

Keywords: dog; dysbiosis; mast cell tumours; microbiota.

Figure 1

(A) Boxplots of alpha diversity metrics (number of Observed ASVs, Shannon Index, and Inverse Simpson Index) of the faecal material in healthy and diseased dogs. Each symbol represents one sample (n = 56, paired samples from 28 healthy and 28 diseased animals). The upper and lower edges of the boxes indicate the first and third quartiles; the line inside the box is the second quartile (median), and individual dots are outliers. * p = 0.019; ns = non-significant paired Wilcoxon test. (B) Ordination plot based on non-metric multidimensional scaling analysis of Bray–Curtis distances at the ASV level. Dots represent individual samples, and SD ellipses are coloured by sample group (healthy and diseased animals). Stress = 0.03 (stress values ≤ 0.1 are considered fair; values ≤ 0.05 indicate a good fit).

Figure 2

Relative bacterial abundance (y-axis) at the phylum and genus taxonomic levels in the faecal samples of the 28 control dogs (CTR) and 28 dogs with MCT (TUM).

Figure 3

Relative proportion of sequences (y-axis) derived from the NGS data of taxa at the phylum (A), class (B), order (C), family (D), and genus (E) levels that are significantly different between faecal samples of 28 healthy (CTR) and 28 diseased dogs (TUM). Only taxa with a relative abundance higher than 1% are represented. p-values for each taxon are presented inside the respective graph.

Figure 4

Venn diagram representation of shared and unique genera across the two groups of the study, generated using Venny URL (accessed on 16 October 2024): https://bioinfogp.cnb.csic.es/tools/venny/.