In adherent mucus compartments of the ileum and colon, which bacterial group was significantly increased in cats with small cell GI lymphoma as compared with cats with IBD?

• A. Fusobacterium spp.
• B. Bacteroides spp.
• C. Clostridium spp.
• D. Enterobacteriaceae

Answer: (B)

In the adherent mucus layer of the ileum and colon, bacteria that are capable of thriving right at the mucosal surface can be highly informative about the local host environment. In cats with small cell GI lymphoma, there is a notable expansion of Bacteroides species within this mucus-associated niche compared with cats with inflammatory bowel disease. Bacteroides are a major group of anaerobic Gram-negative bacteria well-adapted to the mucus-rich environment; they possess enzymes that allow them to utilize mucin-derived sugars and other complex substrates found near the epithelium. Their increased presence in the mucous layer likely reflects changes in the mucosal environment and immune milieu driven by lymphoma, creating conditions that favor mucosa-adherent Bacteroides over other taxa. This specific enrichment helps distinguish the mucosa-associated microbial profile of lymphoma from that of IBD. While other groups such as Fusobacterium, Clostridium, and Enterobacteriaceae are common players in gut dysbiosis, they did not show the same significant rise in this particular mucus-associated compartment for this comparison.