What is the key bacterium suggested for 7α-dehydroxylation in dogs?

• A. Clostridium hiranonis
• B. Escherichia coli
• C. Bacteroides fragilis
• D. Lactobacillus acidophilus

Answer: (A)

7α-dehydroxylation is the microbial step that converts primary bile acids into secondary bile acids, a process carried out by specific anaerobic bacteria that carry the bai genes. In dogs, Clostridium hiranonis is the bacterium most strongly linked to this transformation, contributing to the production of secondary bile acids and helping shape the canine bile acid pool. Other organisms listed do not perform this step as their primary function or capability: E. coli lacks this activity; Bacteroides fragilis may participate in various bile acid processes but is not the main 7α-dehydroxylator in dogs; Lactobacillus acidophilus is known for lactic acid production and bile salt deconjugation rather than 7α-dehydroxylation.