Effect of low dose azithromycin on the fecal microbiome and fecal bile acids in healthy dogs
Colin Smith, Roman Husnik, Frederic Gaschen, Claudia Kirk, Xiaojuan Zhu, Jan SuchodolskiAbstract
Background
Azithromycin has prokinetic effects at low doses in people, cats, and anecdotally, in dogs; however, antibiotics alter the fecal microbiome and metabolome.
Hypothesis/Objectives
To prospectively evaluate the effects of low-dose azithromycin, hypothesizing that it would alter the fecal microbiome and fecal bile acids in healthy dogs.
Animals
Eleven healthy research dogs.
Methods
Prospective study. Dogs received azithromycin (2 mg/kg PO q8h) for 8 days. Fecal samples were collected before (day 1), during (day 6), and after azithromycin administration (days 11, 26, 36, 45). Fecal consistency was assessed daily. Microbiome analysis included qPCR quantification of 16 core bacterial taxa and the Dysbiosis Index. Fecal concentrations of conjugated and unconjugated bile acids (UBAs) were measured on days 1, 11, and 45.
Results
Fecal scores increased during azithromycin administration (P = .009). Abundance of 7 of 16 taxa decreased significantly on day 6, including Peptacetobacter hiranonis (P. hiranonis; P < .001), Faecalibacterium (P < .001), and Fusobacterium (P = .031). Abundance of Streptococcus significantly decreased on day 11 (P = .003). Percentage of primary UBAs increased (P = .017; median, 94.06%; range, 0.73%-96.08%), returned to baseline by day 45, and negatively correlated with abundance of P. hiranonis (r = -0.936 [95% CI, -0.973, -0.852], P < .001). Abundance of 8 of 9 significantly altered taxa recovered, with abundance of Streptococcus remaining decreased.
Conclusions and clinical importance
Low-dose azithromycin induces a mostly reversible dysbiosis and reversible decrease in secondary fecal UBAs. Atypical decreases in Streptococcus abundance can also occur.