Effects of Metronidazole on the Fecal Microbiota, Fecal Metabolites, and Serum Metabolites of Healthy Adult Cats

Antibiotics are commonly used to aid in the remission of gastrointestinal diseases, but usage may lead to prolonged dysbiosis. The objective of this study was to evaluate the effects of metronidazole on fecal microbiota, fecal metabolites, and serum bile acids and uremic toxins of healthy adult cats. Twelve healthy adult cats (4.7±0.4 yr) received metronidazole (20 mg/kg BW PO BID) for 14 days (day 0–14) and were monitored during a 28-day recovery period (day 15–42). Fecal and blood samples were collected at baseline (day 0), after metronidazole (day 14), and weekly during recovery (days 21, 28, 35, and 42). Fecal samples were analyzed for microbiota and bacterial metabolites. Serum samples were analyzed for bile acids and uremic toxins. Metronidazole increased dysbiosis index and fecal lactate concentrations (P<0.0001), and decreased fecal propionate, butyrate, and secondary bile acid concentrations (P<0.0001) for up to 28 days. Prolonged dysbiosis and Peptacetobacter (Clostridium) hiranonis reductions were observed in 10/12 (83%) cats. Serum uremic toxins were also reduced (P<0.0001) after metronidazole administration. The observed changes after metronidazole administration illustrate how changes in the gut microbiome alter microbial metabolism and its relation to host dysmetabolism. In conclusion, metronidazole is a potent antibiotic with persistent effects observed in the microbiome and metabolome, even up to one month after administration.