Successful treatment of Rhodococcus equi P-type infection with subcutaneous abscessation in a foal.

Abstract

Rhodococcus (R.) equi is a common causative agent of the septic arthritis, physitis, and osteomyelitis (SAPO) complex in foals, often resulting from hematogenous dissemination or perforating trauma. The early detection of osteomyelitis is challenging, and treatment has a guarded prognosis.A 3-month-old warmblood filly was presented with severe lameness, swelling, and palpable heat in the right cubital region. Ultrasonographic examination revealed signs suggestive of septic arthritis. Joint lavage and intra-articular injection of antibiotic were performed, but synovial swab cultures were sterile. Subsequently worsened lameness and increased body temperature prompted further investigations, confirming physitis and lung involvement. Definitive R. equi diagnosis was obtained from physeal curettage samples. Surgical drainage and repeated curettage were performed, along with antibiotic therapy based on antibiograms.Radiographic follow-ups showed reduction in bone defect size, and magnetic field therapy was employed during hospitalization, additionally to medical and surgical treatment. Long-term follow-up indicated sustained improvement without recurrence.This case demonstrates that early recognition of R. equi orthopedic infections requires a multidisciplinary approach and comprehensive diagnostic testing, including imaging and culture for antibiogram-guided therapy. In cases of P-type bone infection aggressive surgical treatment, consisting of repeated curettage of the involved physis is essential to address underlying pathology and promote tissue healing. Despite associated challenges and costs, these procedures significantly improve long-term outcomes.