Antimicrobial Susceptibility of Isolated from Sheep with Fibrinous Pneumonia

Abstract

Ovine respiratory complex is a signifi cant cause of death in sheep fl ocks, where Pasteurella multocida is the most frequent microorganisms isolated from animals with pneumonia. There is an urgent need to refi ne the use of different antimicrobials to avoid the problem of antimicrobial resistance and optimize the control of this disease in ovine livestock. The fi rst step in approaching this problem is gaining an insight into the antimicrobial susceptibility of ovine pathogens. This study evaluated the in vitro activity of tildipirosin, gamithromycin, oxytetracycline, and danofl oxacin against Pasteurella multocida strains isolated from sheep with fi brinous pneumonia. The strains were incubated following Clinical and Laboratory Standards Institute (CLSI) standard conditions and also with a modifi ed method by 25% supplementation with sheep serum. Minimum inhibitory concentrations (MIC) were determined using the broth microdilution technique. The lowest MIC90 under standard conditions and by supplementation with sheep serum was obtained with tildipirosin. Sheep serum signifi cantly reduced tildipirosin, gamithromycin, and danofl oxacin MIC values for Pasteurella multocida strains. In brief, the potency of tildipirosine, gamithromycin, and danofl oxacin against Pasteurella multocida increases when sheep serum is added to the culture media.