Effects of potentiated chlorhexidine on bacteria and tarsocrural joints in ponies.

OBJECTIVES: To evaluate the bactericidal properties of chlorhexidine diacetate (CHD) after potentiation with EDTA and Tris buffer (EDTA-Tris), and to find a potentiated CHD concentration that would achieve 90 to 100% killing for all bacteria tested.

ANIMALS: 6 adult ponies.

PROCEDURES: Serial dilutions of CHD, CHD in EDTA-Tris and EDTA-Tris alone were evaluated for bactericidal activity against Staphylococcus aureus, Escherichia coli, and Streptococcus zooepidemicus. The tarsocrural joints of 6 ponies were lavaged with either 1 L phosphate-buffered saline solution (control) or 1 L of 0.0005% CHD in EDTA-Tris. Synovial fluid was collected before lavage and on days 1,4, and 8. Synovia, cartilage, and bone with cartilage were collected on day 8 when the ponies were euthanatized.

RESULTS: In vitro results indicated that 0.0005% CHD in EDTA-Tris was 90% lethal to all bacteria tested. Results of synovial fluid analysis, glycosaminoglycan analysis, and histologic examination of the synovial membrane and articular cartilage indicated that joint lavage with 0.0005% CHD in EDTA-Tris was not detrimental to the synovium or the articular cartilage of pony tarsocrural joints. Changes observed were a result of the actual lavage process, the phosphate-buffered saline solution, and hemarthrosis.

CONCLUSIONS: A concentration of 0.0005% CHD in EDTA-Tris was 90% lethal to all bacteria tested. Pony tarsocrural joint lavage with 0.0005% CHD in EDTA-Tris was not detrimental to the synovium or the articular cartilage. The efficacy of 0.0005% CHD potentiated with EDTA-Tris as a potential joint lavage fluid for treatment of infectious arthritis needs to be evaluated in clinical patients.