Internal Medicine Resident University of Tennessee Knoxville, Tennessee, United States
Abstract:
Background: Azithromycin has prokinetic effects at low doses in people, cats, and anecdotally, in dogs; however, antibiotics are known to negatively impact the fecal microbiome and metabolome. Hypothesis/
Objectives: To prospectively evaluate the effect of azithromycin at a low dose on the fecal microbiome and fecal bile acids over time. Animals: Eleven healthy adult research dogs.
Methods: Dogs received azithromycin (2mg/kg PO q8h) for 8 days and then were monitored for 35 days. Fecal samples were collected before (day 1), during (day 6), and post-azithromycin administration (days 11, 26, 36, 45), and fecal scored daily. The microbiome was assessed using qPCR to determine the abundance of 16 core bacterial taxa and the Dysbiosis Index (DI). Fecal concentrations of conjugated and unconjugated bile acids (UBAs) were measured on day 1, 11, and 45.
Results: Fecal scores and the DI increased during azithromycin administration (p < 0.001 and p = 0.068, respectively). Most bacterial taxa showed decreased abundance on day 6, including Peptacetobacter hiranonis (p < 0.001), with most recovering by day 45. Only Enterococcus increased on day 6 (p < 0.001). An unexpected decrease in Escherichia coli and Streptococcus abundances occurred during azithromycin administration (p = 0.009 and p = 0.053, respectively). Secondary UBAs decreased on day 11 (p = 0.006), but recovered by day 45. Conclusions and Clinical Importance: Low dose azithromycin causes a mostly reversible dysbiosis and decrease in secondary fecal UBAs. Decreased abundance of E. coli and Streptococcus may also occur, which differs from other broad-spectrum antibiotics.
