The effect of Pasteurella haemolytica A2 infection on phagocytosis efficiency of caprine broncho-alveolar macrophages

Antimicrobial susceptibility patterns and sensitivity to tulathromycin in goat respiratory bacterial isolates

Bacterial pneumonia is a common and often life-threatening respiratory problem in both meat and dairy goats. Options for approved antibiotic therapy in goats to combat these bacterial infections are severely limited and frequently drugs must be used in an extra-label manner. Tulathromycin, a triamilide macrolide antimicrobial drug shown to be effective against swine and cattle respiratory bacterial agents, has been identified as a potentially useful drug in caprines. The present study was conducted to determine the susceptibility of recognized bacterial respiratory pathogens to commonly prescribed antimicrobials, with a particular emphasis on the efficacy of tulathromycin against these agents. Minimum inhibitory concentration (MIC) testing using microbroth dilution was performed on a collection of 45 Mannheimia haemolytica, 11 Pasteurella multocida, and 11 Bibersteinia trehalosi isolates from the lungs of goats with clinical pneumonia. To further characterize efficacy of tulathromycin against these pathogens, minimum bactericidal concentration (MBC) testing and kinetic killing assays were conducted. Most isolates were susceptible to the antimicrobials tested; however, increased resistance as demonstrated by higher MIC values was seen in all species to penicillin, in P. multocida to sulfadimethoxine, and in B. trehalosi to the tetracyclines. All isolates were susceptible to tulathromycin, which demonstrated a high killing efficiency in both bactericidal assays. Results of this study indicate that most goat pneumonic bacterial pathogens remain susceptible to commonly prescribed antibiotics, although some evidence of resistance was seen to certain drugs; and that tulathromycin is highly effective against goat respiratory pathogens which could make it a valuable medication in this species.

Tulathromycin assay validation and tissue residues after single and multiple subcutaneous injections in domestic goats (Capra aegagrus hircus)

Tulathromycin is a macrolide antimicrobial labeled for treatment of bacterial pneumonia in cattle and swine. The purpose of the present research was to evaluate tissue concentrations of tulathromycin in the caprine species. A tandem mass spectrometry regulatory analytical method that detects the common fragment of tulathromycin in cattle and swine was validated with goat tissues. The method was used to study tulathromycin depletion in goat tissues (liver, kidney, muscle, fat, injection site, and lung) over time. In two different studies, six juvenile and 25 market-age goats received a single injection of 2.5 mg/kg of tulathromycin subcutaneously; in a third study, 18 juvenile goats were treated with 2.5, 7.5, or 12.5 mg/kg tulathromycin weekly with three subcutaneous injections. Mean tulathromycin tissue concentrations were highest at injection site samples in all studies and all doses. Lung tissue concentrations were greatest at day 5 in market-age goats while in the multi-dose animals concentrations demonstrated dose-dependent increases. Concentrations were below limit of quantification in injection site and lung by day 18 and in liver, kidney, muscle, and fat at all time points. This study demonstrated that tissue levels in goats are very similar to those seen in swine and cattle.