Caprine Abscess Model of Tulathromycin Concentrations in Interstitial Fluid from Tissue Chambers Inoculated with Corynebacterium pseudotuberculosis following Subcutaneous or Intrachamber Administration

Abstract

ABSTRACTCorynebacterium pseudotuberculosiscauses chronic, suppurative, abscessing conditions in livestock and humans. We used anin vivomodel to evaluate antimicrobial efficacy for focal abscesses caused byC. 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 withC. 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 fromC. pseudotuberculosis-infected and control chambers following subcutaneous or intrachamber injection of tulathromycin. In addition, the effects of tulathromycin on the quantity ofC. pseudotuberculosisreisolated from inoculated chambers were assessed over time. Tulathromycin IF concentrations fromC. 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 theC. pseudotuberculosisisolate 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 ofC. pseudotuberculosis15 days postadministration. Results of this study indicate that tulathromycin may be beneficial in the treatment of focal infections such as those caused byC. pseudotuberculosis.