Osteomyelitis in Horses

Equine bone marrow-derived mesenchymal stromal cells reduce established S. aureus and E. coli biofilm matrix in vitro

Biofilms reduce antibiotic efficacy and lead to complications and mortality in human and equine patients with orthopedic infections. Equine bone marrow-derived mesenchymal stromal cells (MSC) kill planktonic bacteria and prevent biofilm formation, but their ability to disrupt established orthopedic biofilms is unknown. Our objective was to evaluate the ability of MSC to reduce established S. aureus or E. coli biofilms in vitro. We hypothesized that MSC would reduce biofilm matrix and colony-forming units (CFU) compared to no treatment and that MSC combined with the antibiotic, amikacin sulfate, would reduce these components more than MSC or amikacin alone. MSC were isolated from 5 adult Thoroughbred horses in antibiotic-free medium. 24-hour S. aureus or E. coli biofilms were co-cultured in triplicate for 24 or 48 hours in a transwell plate system: untreated (negative) control, 30 μg/mL amikacin, 1 x 106 passage 3 MSC, and MSC with 30 μg/mL amikacin. Treated biofilms were photographed and biofilm area quantified digitally. Biomass was quantified via crystal violet staining, and CFU quantified following enzymatic digestion. Data were analyzed using mixed model ANOVA with Tukey post-hoc comparisons (p < 0.05). MSC significantly reduced S. aureus biofilms at both timepoints and E. coli biofilm area at 48 hours compared to untreated controls. MSC with amikacin significantly reduced S. aureus biofilms versus amikacin and E. coli biofilms versus MSC at 48 hours. MSC significantly reduced S. aureus biomass at both timepoints and reduced S. aureus CFU at 48 hours versus untreated controls. MSC with amikacin significantly reduced S. aureus biomass versus amikacin at 24 hours and S. aureus and E. coli CFU versus MSC at both timepoints. MSC primarily disrupted the biofilm matrix but performed differently on S. aureus versus E. coli. Evaluation of biofilm-MSC interactions, MSC dose, and treatment time are warranted prior to testing in vivo.

Antimicrobial Resistance in Equines: A Growing Threat to Horse Health and Beyond-A Comprehensive Review

The equine industry holds substantial economic importance not only in the USA but worldwide. The occurrence of various infectious bacterial diseases in horses can lead to severe health issues, economic losses, and restrictions on horse movement and trade. Effective management and control of these diseases are therefore crucial for the growth and sustainability of the equine industry. While antibiotics constitute the primary treatment strategy for any bacterial infections in horses, developing resistance to clinically important antibiotics poses significant challenges to equine health and welfare. The adverse effects of antimicrobial overuse and the escalating threat of resistance underscore the critical importance of antimicrobial stewardship within the equine industry. There is limited information on the epidemiology of antimicrobial-resistant bacterial infections in horses. In this comprehensive review, we focus on the history and types of antimicrobials used in horses and provide recommendations for combating drug-resistant bacterial infections in horses. This review also highlights the epidemiology of antimicrobial resistance (AMR) in horses, emphasizing the public health significance and transmission dynamics between horses and other animals within a One Health framework. By fostering responsible practices and innovative control measures, we can better help the equine industry combat the pressing threat of AMR and thus safeguard equine as well as public health.

Regional antibiotic perfusion through the lateral saphenous vein in two horses with septic calcaneal osteitis

In this case report, two horses with chronic refractory infections in the tuber calcanei were successfully managed via intravenous antibiotic regional limb perfusion through the lateral saphenous vein after failure of conventional treatment approaches, including surgery and intravenous regional limb perfusion using the cranial branch of the medial saphenous vein. Surgical delay in these cases may have allowed the development of chronic infection, which prevented the conventional regional perfusion from working effectively. The spatial difference of the vessels relative to the tuber calcanei possibly contributed to the treatment outcome in these horses. This report describes a novel approach for regional antimicrobial perfusion to the equine plantar hock region using the lateral saphenous vein.

Case report: Use of penicillin G potassium in poloxamer 407 gel to aid in healing of an equine sublingual abscess

The use of poloxamer 407 gels have been reported in several studies to prolong the release of drugs at the injection site. Oral lesions unrelated to dental disease are rare but may result in ulceration and sequestration of bone. To date, there have been no reports on the use of penicillin G potassium poloxamer 407 gel and its effect on wound healing. The present case report describes the use of a penicillin G potassium poloxamer 407 gel for the treatment of a sublingual abscess involving the mandible in a 20 year old Arabian mare who initially presented with acute onset of dysphagia, hypersalivation, and a mass under the tongue. A presumptive diagnosis of lingual cellulitis was made, and a sublingual abscess ruptured on day 7 of hospitalization. In this case, poloxamer 407 gel was used to decrease wound contamination, protect the exposed mandible, and potentially prolong the release of penicillin G potassium into the wound.

[Severe chronic osteomyelitis of the os ileum in an alpaca - Diagnostic and pathological findings]

A 5.5-year-old alpaca mare was referred to the University Clinic for Ruminants due to a lameness in the right hind limb. Six months prior to presentation, the mare had been treated with systemic antibiotics resulting in resolution of the initial lameness. At the time there had been no indication of an inciting trauma. Clinical examination revealed an approx. 2 × 2 cm large, fluctuating, neither excessively warm nor painful mass caudal to the right tuber coxae fixed to the underlying tissue. In addition, a moderate, mixed lameness with a predominant proportion of the swinging leg component was present in the right hind limb. Subsequently, sonographic examination of the right gluteal region was performed, revealing severe alterations of bone contour in the area of the right hip joint. Radiographic assessment of the pelvis was carried out for further clarification. Based on the clinical finding of a fistula in the right gluteal region as well as the results of the radiologic examination, a long-standing infected fracture of the right iliac bone accompanied by high-degree, irregularly calcified callus formation and low to moderate osteomyelitis in the fracture area was diagnosed. The patient was euthanized in consequence of the grave prognosis. Computed tomographic examination of the pelvis and the lumbar spine in the L3-L6 area was undertaken in order to further document the extent of the pathological changes. For final clarification, patho-histological examination as well as a microbiologic analysis of the abscess exudate were performed.The presented case shows the importance of clinical as well as orthopedic examinations, as the individual animal frequently only exhibits minimal clinical signs despite the presence of severe changes.

Cervical vertebral osteomyelitis secondary to Streptococcus equi infection in an adult horse - case report

ABSTRACT A 15-year-old, mixed breed, male horse was attended with a history of multiple abscesses in the cervical region with a three-year evolution. Upon admission, three fistulous tracts with drainage of purulent secretions in the cervical region, low body score, restriction of cervical movements, and painful sensitivity to palpation were observed. The horse was diagnosed with osteomyelitis secondary to Streptococcus equi infection. The initial treatment was antibiotic therapy and local curative. Owing to the lack of response, surgical debridement was performed. An initial favorable response was observed; however, after 4 months, drainage recurred, and the animal was euthanized. A post-mortem computed tomography scan was performed to obtain details of the injury. Cervical osteomyelitis is rare, and its occurrence through hematogenous spread in adult horses and the tomographic findings had not been reported previously. The long period of evolution, difficulty in performing an aggressive debridement, and the presence of multi-drug resistant bacteria contributed to the negative outcome.

Comparison of conventional radiography and computed tomography as aids in the diagnosis of osteomyelitis in 11 foals

BACKGROUND

Conventional radiography is currently the most common imaging modality used by veterinarians investigating foals with suspected osteomyelitis. Emerging evidence in adult horses and humans suggests computed tomography (CT) is a superior modality for evaluation of osseous changes in general. This study aimed to evaluate the potential benefits of CT versus conventional radiography in cases of osteomyelitis in foals.

METHODS

Cases of osteomyelitis in foals under 6 months of age admitted over a 6-year period at a single referral hospital that had both CT and conventional radiography images were retrieved. Case details and measurements of the largest area of bone lysis identified in two planes (lateromedial/sagittal and dorsopalmar/dorsal) were evaluated by three veterinarians with a range of experience.

RESULTS

A significant difference regarding lesion size was seen on the lateromedial (LM) radiographic projections compared with the equivalent sagittal plane CT image. The LM radiographic evaluation resulted in a 37% underestimation of the area of the lesion. Additionally, use of the LM radiographic projections were 2.5-fold more variable in the measurement area compared with CT. In general, regardless of projection, CT produced more information regarding lesion area and, in some cases, detected osseous changes that were not evident on the radiographs.

CLINICAL RELEVANCE

LM radiographic projections are less reliable and commonly result in an under-appreciation of lesion size and extent. CT detected lesions that were difficult or impossible to identify on radiographs and may allow improved treatment planning.

Minimally invasive repair of a calcaneus fracture in a Standardbred foal

CASE DESCRIPTION

A 4-month-old Standardbred colt was examined because of a fractured right calcaneus of 8 days' duration with increased distraction of the fracture fragment evident on sequential radiographs.

CLINICAL FINDINGS

The foal was severely lame with diffuse periarticular tarsal swelling. Radiographically, a complete, displaced long oblique fracture of the right calcaneal body was evident. Because the fracture gap was increasing with time and lameness remained severe, despite medical management, surgical repair was recommended.

TREATMENT AND OUTCOME

The foal was anesthetized, and minimally invasive fracture reduction and internal fixation were achieved by use of two 4.5-mm cortical screws placed in lag fashion via stab incisions over the lateral aspect of the calcaneus. External coaptation with a Robert-Jones bandage only was used after surgery. The foal recovered well and the fracture healed appropriately, but at 8 weeks following surgery, tenosynovitis of the tarsal sheath had developed. This was attributed to the tip of the distal screw encroaching on the sheath. The screw was removed under anesthesia and the tarsal sheath drained. The tenosynovitis resolved with rest and bandaging. Fourteen months after surgery, the colt was free of lameness.

CLINICAL RELEVANCE

Findings suggested that a minimally invasive internal fixation technique for treatment of a calcaneus fracture in horses may be successful and may be associated with decreased morbidity, compared with the use of open reduction and plate fixation.

Surgical treatment of osteomyelitis and formation of a sequestrum in the distal metaphysis of the humerus in an alpaca cria

CASE HISTORY

An 8-week-old, 16-kg alpaca cria was presented with a 2-week history of acute onset of left forelimb lameness.

CLINICAL FINDINGS

The cria was weight-bearing but lame at the walk in the left forelimb. There was swelling, heat and pain on palpation of the soft tissues, extending from the mid-shaft of the humerus to the elbow. There was no evidence of a traumatic injury. Radiologically, there was evidence of osteomyelitis and a sequestrum involving the distal metaphysis of the humerus. The sequestrum was removed surgically. No bacteria were cultured from samples taken during surgery. After an initial improvement, the cria became acutely lame, and developed an abscess at the surgical site, which was drained. A pure growth of a strictly anaerobic, Gram-negative, non-spore-forming, pleomorphic, filamentous rod was cultured from fluid from the abscess. Further radiographs suggested a second sequestrum was present, and this was removed surgically. Apart from partial dehiscence of the wound, the cria recovered well, and was sound and without complications 18 months after surgery.

DIAGNOSIS

Osteomyelitis and formation of sequestra in the distal metaphysic of the left humerus.

CLINICAL RELEVANCE

There has only been one case of osteomyelitis and bone sequestration without evidence of trauma in alpaca crias reported in the literature. However, anecdotal reports by veterinary practitioners described similar cases of osteomyelitis and bone sequestration, usually affecting the long bones. Further investigation of osteomyelitis and bone sequestration in crias is needed, to define the incidence, determine the pathogenesis, and develop specific recommendations for prevention and treatment.

Surgical treatment of osteomyelitis and sequestration of the ilium by a cranial partial hemipelvectomy in an alpaca cria

A 12-week-old female alpaca cria weighing 10 kg presented with a 2-month history of left hindlimb lameness associated with osteomyelitis and sequestration of the shaft and wing of the left ilium. The affected segment of the ilium was surgically removed. Bacteriological culture revealed a small number of mixed aerobic and anaerobic bacteria. The cria recovered well, was discharged from the hospital 8 days after surgery and was paddock sound without complications 8 months later. Osteomyelitis and sequestration of long bones has been reported in alpacas, but further investigation is necessary to define the prevalence and pathogenesis and to develop specific recommendations for prevention and treatment.

Disseminated abscessation complicated with bone marrow abscess caused by Arcanobacterium pyogenes in a goat

An 8-month-old, Nubian wether with a history of systemic illness was euthanatized for a pathological examination. At necropsy, the presence of disseminated abscessation and cellulitis in the limbs was noted. Other postmortem findings associated with the visceral disease in this animal included multiple abscess lesions, mainly in the lungs, kidneys, phalanxes and vertebrae. Histopathologically, lesions of arteriolitis were found as evidenced by bacterial embolisms in pulmonary and renal arteriola, indicating a bacteremia in the patient. Arcanobacterium pyogenes was consistently isolated from 8 lesions of abscessations, including the lesions of subcutaneous abscesses as well as bone marrow abscess in phalanxes and thoracic vertebrae. This is the first published report of disseminated arcanobacterial infection with bone marrow abscess of both the phalanxes and vertebrae in goat.