Toxicities of Different Concentrations of Commonly Used Antibiotics on Canine Chondrocyte and Synovial Cell Cultures

Introduction: Septic arthritis (SA) causes debilitating lameness in dogs, necessitating antimicrobial treatment. Long-term systemic antibiotic therapy may cure SA but results in patient side effects, lack of owner compliance, and development of multidrug resistant infections. Intra-articular (IA) antibiotic injection may shorten treatment time and reduce costs and side effects. The objective of this study was to evaluate the effects of antibiotics commonly used in canine practice on joint cell viability to determine safe IA doses.

Materials and Methods: Canine chondrocytes and synoviocytes were harvested from three dogs, expanded in culture and plated. Cells were exposed to six antibiotics at seven concentrations. Cell viability was assessed by trypan blue dye exclusion and 7-AAD with flow cytometric quantification. The concentration at which 50% cells were viable was determined. Cell death mechanism was evaluated using human mouse active caspase 3 antibody to assess for apoptosis. Statistical analysis was performed with significance assessed at p < 0.05.

Results: Antibiotics expressed dose-dependent but variable cytotoxicity to canine joint cells. Caspase 3 expression was elicited from cells following exposure to all antibiotics evaluated except ampicillin sulbactam. Vancomycin and ampicillin sulbactam represent less toxic alternatives for IA antibiotics.

Discussion/Conclusion: These data provide important information to practitioners to guide dosing strategies for IA antibiotic usage. Further studies are necessary to extrapolate these results to the in vivo joint environment.

Acknowledgment: The authors declare no conflicts of interest. This study was funded by the Shipley Foundation and supported by NIH/NCATS Colorado CTSA Grant Number TL1TR002533. Contents are the authors’ sole responsibility and do not necessarily represent official NIH views.