Septic Arthritis, Tenosynovitis, and Infections of Hoof Structures

TLR-activated mesenchymal stromal cell therapy and antibiotics to treat multi-drug resistant Staphylococcal septic arthritis in an equine model

BACKGROUND

Rapid development of antibiotic resistance necessitates advancement of novel therapeutic strategies to treat infection. Mesenchymal stromal cells (MSC) possess antimicrobial and immunomodulatory properties, mediated through antimicrobial peptide secretion and recruitment of innate immune cells including neutrophils and monocytes. TLR-3 activation of human, canine and equine MSC has been shown to enhance bacterial killing and clearance in vitro, in rodent Staphylococcal biofilm infection models and dogs with spontaneous multi-drug-resistant infections. The objective of this study was to determine if intra-articular (IA) TLR-3-activated MSC with antibiotics improved clinical parameters and reduced bacterial counts and inflammatory cytokine concentrations in synovial fluid (SF) of horses with induced septic arthritis.

METHODS

Eight horses were inoculated in one tarsocrural joint with multidrug-resistant Staphylococcus aureus (S. aureus). Bone marrow-derived MSC from three unrelated donors were activated with TLR-3 agonist polyinosinic, polycytidylic acid (pIC). Recipient horses received MSC plus vancomycin (TLR-MSC-VAN), or vancomycin (VAN) alone, on days 1, 4, 7 post-inoculation and systemic gentamicin. Pain scores, quantitative bacterial counts (SF, synovium), SF analyses, complete blood counts, cytokine concentrations (SF, plasma), imaging changes (MRI, ultrasound, radiographs), macroscopic joint scores and histologic changes were assessed. Results were reported as mean ± SEM.

RESULTS

Pain scores (d7, P=0.01, 15.2±0.2 vs. 17.9±0.5), ultrasound (d7, P=0.03, 9.0±0.6 vs. 11.8±0.5), quantitative bacterial counts (SF d7, P=0.02, 0±0 vs. 3.4±0.4; synovium P=0.003, 0.4±0.4 vs. 162.7±18.4), systemic neutrophil (d4, P=0.03, 4.6±0.6 vs. 7.8±0.6) and serum amyloid A (SAA) (d4, P=0.01, 1,106.0±659.0 vs. 2,858.8±141.3; d7, P=0.02, 761.8±746.2 vs. 2,357.3±304.3), and SF lactate (d7, P<0.0001, 5.4±0.2 vs. 15.0±0.3), SAA (endterm, P=0.01, 0.0 vs. 2,094.0±601.6), IL-6 (P=0.03, 313.0±119.2 vs. 1,328.2±208.9), and IL-18 (P=0.02, 11.1±0.5 vs. 13.3±3.8) were improved in TLR-MSC-VAN vs. VAN horses. Study limitations include the small horse sample size, short study duration, and lack of additional control groups.

CONCLUSIONS

Combined TLR-activated MSC with antibiotic therapy may be a promising approach to manage joint infections with drug resistant bacteria.

A scoping review of the current evidence on treatment and outcomes following synovial sepsis

BACKGROUND

Synovial sepsis is a frequent cause of morbidity and mortality in horses. Despite advances in diagnostics and treatments, persistent infection or chronic lameness can occur.

OBJECTIVES

To perform a scoping review to identify and evaluate the current evidence on the factors implicated in the success of treatment for synovial sepsis.

STUDY DESIGN

Joanna Briggs Institute scoping review.

METHODS

A protocol was registered, and a systematic literature search was performed on CAB abstracts, Medline, Scopus and Embase. Inclusion and exclusion criteria were developed and studies systematically reviewed against this. Studies relating to factors affecting treatment success following synovial sepsis were retained and data was extracted on study method, population characteristics and factors significantly associated with treatment outcome.

RESULTS

In total, 2338 studies were identified, and 61 were included to full paper analysis. Eight papers reported significant factors, identifying 15 risk factors associated with two measurements of outcome, either survival and/or return to athletic function. The 15 factors were identified and categorised into pre-, intra- and post-operative factors. Risk factors that were identified included the number or type of synovial structures involved, the presence of pannus, tendon and bone pathology, and the use of systemic antimicrobials. There were many discrepancies in inclusion criteria of cases of synovial sepsis as well as measurement and description of outcome variables.

MAIN LIMITATIONS

Non-English language studies or conference proceedings were not included. Only small numbers of papers had similar findings.

CONCLUSIONS

Standardisation of inclusion criteria is essential to enable comparisons and analysis between studies on synovial sepsis. Future studies should use methodologies to reduce bias including multicentre and multinational studies, prospective study design and robust statistical modelling.

A month in a horse's life: healing process of a fractured third metatarsal bone from medieval Viljandi, Estonia

The remains of a horse's hind foot - a third metatarsal bone and three phalanges - were found in a presumed waste pit of a prosperous medieval household in Viljandi, Estonia, dated from the second half of the 13^th to the beginning of the 15^th century. The metatarsal bone had been broken during the horse's lifetime and showed evidence of partial healing. Using archaeological, zooarchaeological, morphological, microscopic, densitometric and radiographic analyses, we investigated the bones and the healing process in order to understand animal treatment in a medieval urban context. Our results show that the fracture was a complete comminuted fracture that appears to have been closed and stable, caused most probably by a trauma from a strong impact. Based on callus formation and the worn edges of the separated diaphysis, the horse had survived for at least a month and used the injured foot to some extent. We suggest that the horse was treated by splinting the foot and keeping the animal in a standing position during the healing process. Eventually the horse died because of a wound infection, or was killed. The relatively long period of careful treatment indicates the animal's economic or emotional value.

Gram-negative multi-drug resistant bacteria influence survival to discharge for horses with septic synovial structures: 206 Cases (2010-2015)

Bacterial colonization of synovial structures can cause infections that are difficult to treat. Systemic and local antimicrobials and repeated joint lavages are the mainstays of therapy. However, despite aggressive treatments, infection may persist, leading to significant tissue damage or death of the patient. In order to investigate the impact of bacterial culture and antimicrobial resistance on survival to discharge, we reviewed medical records of horses admitted to the University of Pennsylvania's large animal teaching hospital from 2010-2015. Two-hundred and six cases with a definitive diagnosis of septic synovitis and a synovial fluid sample submitted for microbiological culture were included in the study. Of these horses, 48% were culture negative and 52% were positive for any bacterial growth, of which 66% were gram-positive and 28% were gram-negative aerobic organisms with 4% anaerobic and 2% fungal organisms. Overall survival to discharge from hospital was 86%. Horses that had negative growth on culture were more likely to survive until discharge (p < 0.02). Multivariable analyses revealed that the likelihood of euthanasia was significantly associated with identification of coagulase positive Staphylococcus spp. (OR 7.66, 5.46-10.74, p < 0.0001), β-hemolytic Streptococcus spp. (OR 5.18, 3.56-7.55, p < 0.0001), Enterococcus spp. (OR 18.38, 11.45-29.52, p = 0.002), Enterobacteriaceae (OR 31.37, 22.28-44.17, p < 0.0001), Pseudomonas aeruginosa (OR 9.31, 5.30-16.34, p = 0.0004) or other gram-negative species (OR 3.51, 2.07-5.94, p = 0.001). Multi-drug resistance and gram-negative bacteria species were associated with significantly decreased survival rates (OR 119.24, 70.57-201.46, p < 0.0001). In conclusion, prognosis for survival to discharge was poor for horses that were infected with gram-negative organisms, particularly those with MDR phenotypes.

Pharmacokinetics of ceftazidime after regional limb perfusion in standing horses

OBJECTIVE

To determine the metacarpophalangeal joint fluid concentrations of ceftazidime administered via regional limb perfusion (RLP).

ANIMALS

Eight healthy horses.

METHODS

RLP was performed by injecting 2 g of ceftazidime and 60 mL of perfusate volume in the cephalic vein of standing, sedated horses. Serum and synovial fluid from the metacarpophalangeal joint were collected before perfusion and at 0.5, 2, 6, 12, 24 hours postperfusion. Ceftazidime concentrations were measured via liquid chromatography. Maximal concentration (C_max ), area under the curve (AUC), half-life of the drug (T ½), and the timing of C_max (T_max ) were determined to assess ceftazidime as a candidate drug for RLP. Continuous parameters were compared with the Mann-Whitney U test. P value ≤ .05 was considered statistically significant.

RESULTS

The C_max of ceftazidime in synovial fluid (235 µg/mL) was 15 times higher than the minimal inhibitory concentration (MIC) for most bacteria involved in orthopedic infections, including resistant pathogens such as Pseudomonas aeruginosa (MIC = 16 µg/mL). However, synovial concentrations decreased quickly and remained above the MIC in only 1 horse by 6 hours postperfusion.

CONCLUSION

RLP generated high synovial fluid concentrations of ceftazidime in the distal limb, but these concentrations decreased rapidly below the deliberately high MIC selected.

CLINICAL RELEVANCE

Once daily RLP, as applied in our study, with 2 g ceftazidime in standing horses, cannot be recommended for use in a clinical setting.

Therapeutic Use of Regional Limb Perfusion in a Chicken

A 2-year-old, 3.8-kg male Rhode Island red rooster was examined for lameness and progressive swelling of the right foot of several month's duration. Radiographs of the right foot demonstrated soft tissue swelling and a smoothly marginated periosteal reaction evident of inflammation affecting the bones. Results of a complete blood count showed a moderate leukocytosis and an elevated total protein concentration. Systemic antibiotic and anti-inflammatory therapy was started, but the bird had not improved at recheck examination. After intravenous catheterization of the medial metatarsal vein and placing a tourniquet at the femoral-tibiotarsal joint of the right leg, regional limb perfusion with amikacin and flunixin meglumine was performed. Dimensions of both feet were measured with digital calipers, and surface temperatures of the feet were measured with an infrared thermometer. The rooster had improved activity level with decrease in lameness and measurable decrease in swelling of the right foot. Regional limb perfusion with intravenous antibiotics and nonsteroidal anti-inflammatory drugs is a viable treatment modality in avian species for suspected distal limb infection and cellulitis. This technique has potential valuable implications for a variety of avian species. Fluid support should be provided if using nephrotoxic drugs.

Serum and Synovial Fluid Serum Amyloid A Response in Equine Models of Synovitis and Septic Arthritis

OBJECTIVE

To investigate the serum and synovial fluid serum amyloid A (SAA) response in equine models of synovitis and septic arthritis and to compare handheld and validated immunoturbidometric assays for SAA quantification.

STUDY DESIGN

Controlled, experimental study.

ANIMALS

Healthy adult horses (n = 9).

METHODS

Synovitis (n = 4) and septic arthritis (n = 5) were induced using lipopolysaccharide and Staphylococcus aureus, respectively, and serial serum and synovial fluid samples were collected. Serial synovial fluid cytology was performed for both models and synovial fluid from the septic arthritis model was submitted for bacterial culture. Serum and synovial fluid SAA were quantified by handheld test and immunoturbidometric assay. Cytologic and SAA data were compared within and between models (mixed model ANOVA) and results of SAA assays were compared using category-by-category analysis (weighted kappa coefficient).

RESULTS

Synovial fluid total nucleated cell counts and total protein increased significantly following induction of both models. Serum and synovial fluid SAA remained normal in synovitis horses and increased significantly in septic arthritis horses. Serum SAA increased more rapidly than synovial fluid SAA. Agreement was 98% when SAA concentrations were low (<50 μg/mL) but the assays diverged when concentrations were greater than ∼100 μg/mL. Overall, there was good category-by-category agreement between SAA assays (weighted kappa = 0.824).

CONCLUSION

Serum and synovial fluid SAA may be useful adjuncts in diagnosing septic arthritis in horses. SAA concentrations for the assays diverged and examination using a larger sample size is needed before direct numeric comparisons between the assays can be made.

The Effect of Perfusate Volume on Amikacin Concentration in the Metacarpophalangeal Joint Following Cephalic Regional Limb Perfusion in Standing Horses

OBJECTIVE

To determine the influence of 3 perfusate volumes on amikacin concentration in the metacarpophalangeal joint following cephalic regional limb perfusion (RLP) in standing horses.

ANIMALS

Seven healthy horses.

METHODS

Three perfusate volumes (100, 60, and 30 mL), containing 2 grams of amikacin, were tested during intravenous RLP at the cephalic vein, placing the tourniquet at mid antebrachium, in standing sedated horses. Synovial fluid was collected from the metacarpophalangeal joint before perfusion and at 30 and 120 minutes after perfusion. Serum samples were taken from the jugular vein at the same time points. Samples were analyzed for amikacin concentrations and a repeated measures ANOVA, followed by least squares difference pairwise comparisons to identify differences in amikacin concentration across perfusate volumes. Differences were considered significant at P<.05.

RESULTS

The mean amikacin concentration in synovial fluid at 30 minutes after perfusion was significantly higher following perfusate volume of 100 mL (579 μg/mL), compared to volumes of 60 mL (227 μg/mL) or 30 mL (282 μg/mL) (P<.05). When a threshold of 160 μg/mL was used, more horses reached the synovial therapeutic threshold following perfusate volume of 100 mL (100%), than horses receiving 60 mL (43%) and 30 mL (57%) at 30 minutes after injection.

CONCLUSION

The use of 100 mL volume for RLP at the cephalic vein in standing horses resulted in higher concentration of amikacin in the synovial fluid and is recommended for use in clinical cases.

Comparison of Arthroscopic Lavage and Needle Lavage Techniques, and Lavage Volume on the Recovery of Colored Microspheres From the Tarsocrural Joints of Cadaver Horses

OBJECTIVE

To quantify recovery of colored microspheres from normal cadaver tarsocrural joints using arthroscopic or needle lavage with 1-5 L of fluid.

STUDY DESIGN

Ex vivo experimental study.

ANIMALS

Adult Quarter Horse cadavers (n = 8).

METHODS

After euthanasia, 1.5 × 10(6)  colored microspheres were injected into each tarsocrural joint. Each joint was randomly assigned to receive lavage (5 L 0.9% NaCl) with an arthroscope (dorsomedial arthroscope and dorsolateral egress cannula) or three 14 g needles (dorsomedial ingress, dorsolateral, and plantarolateral egress). Egress fluid from each liter was collected separately over time and the number of microspheres present in each recovered liter determined by spectrophotometry.

RESULTS

A significant interaction was present between treatment group and liter of fluid (P < .01). The number of microspheres recovered in the first liter of lavage fluid was significantly higher in the needle lavage group than in the arthroscopic lavage group (P < .01). For both groups, the number of microspheres recovered in the first liter of lavage fluid represented a majority of the total microspheres collected and was significantly different from each subsequent liter collected (P < .01). The number of microspheres recovered did not differ between liters 2, 3, 4, and 5 within or between treatment groups.

CONCLUSION

In this model, tarsocrural lavage with three 14 g needles was more effective at removing colored microspheres from the joint than arthroscopic lavage, suggesting that the number or placement of portals present may be more important than portal size and flow rate. No difference in microsphere recovery was seen with lavage volumes >1 L.

Clinical use of antimicrobial regional limb perfusion in horses: 174 cases (1999-2009)

OBJECTIVE

To describe the clinical use of regional limb perfusion with antimicrobials (A-RLP), complications, and outcome in a large series of patients.

DESIGN

Retrospective case series.

ANIMALS

174 horses.

PROCEDURES

Medical records of horses treated with A-RLP between 1999 and 2009 were reviewed. Signalment, primary complaint, horse use, etiology, duration of clinical signs, previous treatment, structures involved, concurrent conditions, A-RLP characteristics, additional treatments, complications, and outcome were recorded. At long-term follow-up, 2 outcomes were investigated: survival rate and return to previous use at the same or higher level. Univariate and multivariate logistic regression analyses were conducted.

RESULTS

Group 1 (96 horses) included septic synovitis. Group 2 (50 horses) included extrasynovial lacerations (23 horses) and fresh, minimally contaminated intrasynovial lacerations without evidence of established synovial infection (27 horses). Group 3 (28 horses) included miscellaneous other conditions. Only minor complications were reported in 12.26% of horses that received IV (n = 155) and 33% of horses that received intraosseous (27) A-RLP. Horses with septic synovitis had a lower survival rate (53.43%) than did horses with lacerations (91.89%). Within group 2, no significant differences in short- or long-term outcomes were found between horses with extrasynovial and fresh, minimally contaminated intrasynovial lacerations. For the horses returning to previous use, 80% of horses with septic synovitis and 72.72% of horses with lacerations were performing at the same or higher level at the time of follow-up.

CONCLUSIONS AND CLINICAL RELEVANCE

The results of the present study indicated that A-RLP is a safe technique with minimal adverse effects. The IV route presented fewer complications than intraosseous injection. Horses with infection of synovial structures had a lower survival rate than did those with acute, minimally contaminated intrasynovial lacerations. The latter had a similar prognosis for horses with extrasynovial lacerations treated with A-RLP.

Tenosynoviotomy for sepsis of the digital flexor tendon sheath in 9 horses

OBJECTIVE

To describe a tenosynoviotomy technique for treatment of sepsis of the digital flexor tendon sheath (DFTS) in horses and report long-term outcome.

STUDY DESIGN

Case series.

ANIMALS

Horses (n = 9).

METHODS

Horses were positioned in lateral recumbency with the affected limb uppermost. A linear incision was made just lateral to the mesotenon beginning 5 cm proximal to the apices of the proximal sesamoid bones, extending 2 cm distal to the bifurcation of the superficial digital flexor tendon (SDFT). The incision was continued through the skin, subcutaneous tissue, palmar/plantar annular ligament, and DFTS. Tenotomy of the distal lateral branch of the SDFT was also performed. The site was thoroughly debrided, lavaged, and packed with gauze and allowed to heal by second intention. Follow-up was obtained via owner telephone interview.

RESULTS

Mean surgery time was 32 minutes (range, 10-64 minutes). Systemic antibiotics were administered postoperatively (range, 11-46 days; mean, 23 days). Mean hospitalization was 11 days (range, 0-49 days). Follow-up was available for 7 (70%) horses. One year postoperatively, 5 (71%) horses were serviceable for their intended use, and 2 (29%) had been euthanatized. Of 5 survivors, 3 returned to ridden exercise, 1 was retired as a broodmare, and 1 was a broodmare. All owners were satisfied with the cosmetic appearance of the surgery site.

CONCLUSION

Open drainage via tenosynoviotomy, performed as a salvage procedure, represents a feasible treatment for DFTS sepsis.

Effect of experimentally induced synovitis on amikacin concentrations after intravenous regional limb perfusion

OBJECTIVES

To determine the effects of experimentally induced synovitis of the radiocarpal joint on the intra-articular pharmacokinetics and pharmacodynamics of amikacin after intravenous regional limb perfusion (IVRLP).

STUDY DESIGN

Randomized crossover experimental design.

ANIMALS

Adult horses (n = 8).

METHODS

Horses were randomly assigned into 2 trials: synovitis and no-synovitis. Radiocarpal joint synovitis was induced with lipopolysaccharide 6 hours before IVRLP. IVRLP (5-mg/kg amikacin qs 60 mL) was performed with a pneumatic tourniquet under general anesthesia. Synovial fluid was obtained before and 0.5, 1, 3, 5, 12, 24, 48 hours after IVRLP. Amikacin concentrations at each time point and pharmacokinetic values were compared between synovitis and no-synovitis trials with Student's t-test.

RESULTS

Amikacin synovial fluid concentrations indicated suspected tourniquet failure on 3 occasions (2 synovitis, 1 no-synovitis) on 3 different horses. Data from both trials in these 3 horses were excluded from further analysis. Observed time to maximal concentration (T(max); mean ± SD = 54 ± 13.42 min) was reached earlier in synovitis joints (5/5, 30 min) than in no-synovitis joints (1/5, 30 min and 4/5, 1 h; P = .0476) (P = .0161). Mean observed maximal concentration (C(max)) was higher in synovitis joints (144.48 ± 43.17 μg/mL) than in no-synovitis joints (60.02 ± 28.81 μg/mL; P = .0301). The recommended C(max): minimum inhibitory concentration ratio of 8 was achieved in 3/5 of the successfully perfused joints with induced synovitis, but this ratio was not achieved in any of the clinically normal joints.

CONCLUSION

Synovitis of the radiocarpal joint resulted in an earlier observed T(max) and higher observed C(max) of intra-articular amikacin after IVRLP compared with normal joints.