The intestinal microbiota is thought to play a major role in the pathogenesis of intestinal disease. Antibiotics are commonly employed in the treatment of acute and chronic enteropathy, in some cases with the goal of eradicating specific pathogens. The aim of this study was to prospectively evaluate the impact of tylosin administration on specific bacterial components of the fecal microbiota.

Sixteen healthy pet dogs were randomly assigned to one of two groups in a double-blinded fashion: Eight dogs were given oral tylosin at 20 mg/kg while the other 8 dogs were administered a placebo capsule, each given q 12 h for 7 days. All dogs were maintained on their usual diet and a standardized fecal score (range: 1 to 7) was noted daily during drug administration. Fecal samples were collected on day 0 prior to drug administration as well as on days 7, 10, 21, and 63. Fecal samples were assessed using quantitative PCR for 7 bacterial taxa, belonging to the Firmicutes, Proteobacteria and Fusobacteria phyla. Relative abundance of Clostridium perfringens was also assessed pre- and post-treatment via qPCR. Parameters were compared using a Friedman's test, followed by Dunn's post-test. A p-value <0.05 was considered statistically significant.

None of the dogs in either group developed diarrhea, though significant changes were seen in the abundance of various bacterial taxa. Significantly decreased Faecalibacterium, Clostridium hiranonis, Turicibacter and Fusobacterium were observed in the fecal microbiota of dogs treated with tylosin at day 7. At 2 months post-tylosin cessation, 5 and 4 of 6 dogs failed to have regained their pre-treatment Faecalibacterium and C. hiranonis levels, respectively. Tylosin administration was not associated with a significant decrease of C. perfringens (p=0.38), but dogs in the placebo group had a significant decrease in C. perfringens (p=0.02). There was no significant change in relative abundance of E. coli in dogs treated with tylosin (p=0.64) or placebo (p=0.38).

Tylosin leads to alterations in the fecal microbiota without predictable effects of potential enteric pathobionts. Further studies are warranted to determine the long-term effects of antimicrobial-induced changes as well as the efficacy of recommended therapies for bacterial enteritis.

Disclosures

Disclosures to report.
Some authors are employed by the Texas A&M GI lab which offers tests on a fee basis. The study was funded by grants from the Comparative Gastroenterology Society and Naniboujou Research Legacy.