Abstract
Pyomyositis is an uncommon primary bacterial infection of skeletal muscles, usually caused by Staphylococcus aureus. Predisposing factors for pyomyositis include immunodeficiency, trauma, injection drug use, concurrent infection and malnutrition. The diagnosis, staging of the disease and differential diagnosis are established by ultrasound, CT and MRI. Treatment involves surgical drainage and antibiotic therapy. We report a case of abdominal rectus muscle pyomyositis, which constitutes, as far as we know, the second reported in bibliography, while Prevotella disiens is firstly reported as causative agent.