Evaluation of Intra-Articular Amikacin Administration in an Equine Non-inflammatory Joint Model to Identify Effective Bactericidal Concentrations While Minimizing Cytotoxicity

Abstract

Septic arthritis causes significant morbidity and mortality in veterinary and human clinical practice and is increasingly complicated by multidrug-resistant infections. Intra-articular (IA) antibiotic administration achieves high local drug concentrations but is considered off-label usage, and appropriate doses have not been defined. Using an equine joint model, we investigated the effects of amikacin injected at three different doses (500, 125, and 31.25 mg) on the immune and cartilage responses in tibiotarsal joints. Synovial fluid (SF) was sampled at multiple time points over 24 h, the cell counts determined, and amikacin concentrations measured by liquid chromatography-mass spectrometry. Cytokine concentrations and collagen degradation products in SF were measured by ELISA and multiplex immunoassays. The mean amikacin concentrations in SF were greater than or equal to the minimum inhibitory concentration (MIC) (0.004 mg/ml) for most common equine joint pathogens at all time points tested to 24 h for all three amikacin doses evaluated. The inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) increased significantly in SF in the highest amikacin dose group, despite the fact that increases in SF cell counts were not observed. Similarly, the biomarkers of cartilage type II collagen cleavage (C2C and C12C) were increased in SF following amikacin injection. Mechanistically, we further demonstrated using in vitro studies that chondrocytes and synoviocytes killed by exposure to amikacin underwent apoptotic cell death and were phagocytosed by macrophages in a non-inflammatory process resembling efferocytosis. Neutrophils and T cells were susceptible to amikacin cytotoxicity at clinically relevant doses, which may result in blunting of cellular inflammatory responses in SF and account for the lack of increase in total nucleated cell counts following amikacin injection. In summary, decisions on whether to inject cytotoxic antibiotics such as aminoglycosides intra-articularly and what doses to use should take into account the potential harm that antibiotics may cause and consider lower doses than those previously reported in equine practice.

A Descriptive Study of the Clinical Presentation, Management, and Outcome of Horses with Acute Soft Tissue Trauma of the Tarsus and the Association with Synovial Involvement

“…These findings might be partly due to the frequent use of local administration of antimicrobials, either intrasynovial or via regional limb perfusion in our study. Local delivery of antimicrobials is increasingly used and is effective in achieving high concentrations in the specific region, while decreasing the treatment cost and the potential side effects of systemic administration [ 33 , 34 , 35 , 36 ]. There has been considerable research on regional limb perfusion protocols in experimental settings [ 37 , 38 , 39 , 40 ] but very limited reports on frequency and efficacy of local antimicrobial administration in naturally occurring traumatic injuries and in SI in horses [ 39 ].…”

Arthroscopic debridement and lavage of a fetlock joint in a British blue calf

“…Its intended purpose is to ensure local concentrations of antibiotic exceed minimum inhibitory concentrations in the joint for a period of time. Amikacin has been shown to exceed minimum inhibitory concentrations for over 24 hours when used intra‐articularly in horses 27 . However, one study in calves showed no difference in clinical outcome if gentamicin was administered intra‐articularly in addition to systemic use 28 .…”

“…Amikacin has been shown to exceed minimum inhibitory concentrations for over 24 hours when used intra-articularly in horses. 27 However, one study in calves showed no difference in clinical outcome if gentamicin was administered intra-articularly in addition to systemic use. 28 Gentamicin-impregnated implants exist that can be placed in the joint and allow sustained release.…”

Current treatment and prevention of orthopaedic infections in the horse

“…For example, injection of 150 mg of gentamicin has been shown to yield 1000-fold higher concentrations in synovial fluid when compared to systemic administration of a 6.6 mg/kg bwt IV dose, and concentrations remain above the MIC for many equine pathogens for more than 24 h (Lloyd et al, 1990). Repeated intrasynovial injections can be performed easily on most horses and should be considered in cases of synovial sepsis (Pezzanite, Chow, Hendrickson, et al, 2021).…”