Synovial fluid pH, cytologic characteristics, and gentamicin concentration after intra-articular administration of the drug in an experimental model of infectious arthritis in horses.

This research investigated the effects and antibacterial activity of the drug gentamicin on septic synovial fluid in horses. The study induced septic arthritis in horses with E. coli bacteria and explored the changes following the administration of gentamicin in different ways, tracking changes in pH, cell count, and gentamicin concentration.

Study Design

• The research was conducted on sixteen clinically normal adult horses. Each horse was inoculated with approximately 7.5 X 10(6) colony-forming units of E. coli bacteria in one antebrachiocarpal joint to stimulate septic arthritis, a painful condition where a joint becomes infected.
• Post inoculation, the horses displayed clinical signs of septic arthritis after 24 hours. The horses were then divided into three groups.
• Group 1 consisted of five horses, each given 150 mg of gentamicin intra-articularly. Group 2 also consisted of five horses, but each was given 2.2 mg of gentamicin per kg of body weight intravenously every six hours. Group 3 contained the remaining six horses, each administered with buffered gentamicin, made of sodium bicarbonate and gentamicin, intra-articularly.
• Samples of synovial fluid were collected at various times post-treatment (0, 0.25, 1, 4, 8, 12 and 24 hours) through an in-dwelling intra-articular catheter. Additionally, the pH of the synovial fluid was measured at 0, 0.25, and 24 hours post-treatment.

Results

• Before inoculation, the E. coli bacteria were isolated from the synovial fluid of all the horses. This confirmed the successful creation of an infection.
• It was noted that at post-treatment hour 0, the synovial fluid had lower pH levels, ranging from 7.08 to 7.16, and a notably higher white blood cell (WBC) count (range 88,000 to 227,200 cells/microliters). This change indicated that the immune system of the horses was responding to the infection.
• The cells in the increased WBC count were predominantly neutrophilic (95 to 99%), suggesting a substantial immune response, as neutrophils are the most common type of white blood cell and are usually the first to respond to infections.
• The concentrations of gentamicin in the synovial fluid were measured, but the specific findings were not included in the abstract.

Conclusion

• The initial findings show that the model for inducing septic arthritis in horses was successful, and changes in the synovial fluid in response to gentamicin administration were clearly observable. However, the full article is needed to understand the overall findings, as the abstract does not include the end results of this study.