Corynebacterium pseudotuberculosis causes chronic, suppurative, abscessing conditions in livestock and humans. We used an in vivo model to evaluate antimicrobial efficacy for focal
abscesses caused by C. pseudotuberculosis. Tissue chambers were surgically implanted in the subcutaneous tissues of the right and left paralumbar fossa of 12 goats to serve as a model for isolated, focal
abscesses. For each goat, one tissue chamber was inoculated with C. pseudotuberculosis, while the contralateral chamber served as an uninoculated control. Six goats were administered a single dose of
tulathromycin at 2.5 mg/kg of
body weight subcutaneously, while the other six received the same dose by injection directly into the inoculated chambers. Our objective was to compare the effects and
tulathromycin concentrations in interstitial fluid (IF) samples collected from C. pseudotuberculosis-infected and control chambers following subcutaneous or intrachamber injection of
tulathromycin. In addition, the effects of
tulathromycin on the quantity of C. pseudotuberculosis reisolated from inoculated chambers were assessed over time.
Tulathromycin IF concentrations from C. pseudotuberculosis-infected and control tissue chambers were similar to those in plasma following subcutaneous administration. Following intrachamber administration,
tulathromycin IF concentrations in infected chambers were continuously above the MIC for the C. pseudotuberculosis isolate for 15 days. There were no significant differences for plasma area under the curve and elimination half-lives between subcutaneous and intrachamber administration. Six of the 12 infected chambers had no growth of C. pseudotuberculosis 15 days postadministration. Results of this study indicate that
tulathromycin may be beneficial in the treatment of
focal infections such as those caused by C. pseudotuberculosis.