MSSA Bacteremia; But Where Does it Originate?

Introduction MSSA bacteremia can result from multiple etiologies and searching for a source is important to avoid potential complications. A rare etiology is pyomyositis; a purulent skeletal muscle infection with localized abscess formation. It classically occurs in tropical countries. Case Description A 23-year-old athletic female presented with lower back pain radiating to the right leg. The pain is throbbing and aggravated by movement. She denied fever or weakness. On exam she was stable and had a positive straight-leg-test. Labs showed a leukocytosis of 15. A spinal-CT demonstrated L4-L5 disc bulge. She was sent home on NSAIDs. However, she returned with spiking fever. Her leukocytosis jumped to 26. Blood cultures grew MSSA within 24hours and continued to grow on 3 separate occasions despite vancomycin use. A TEE ruled-out infective endocarditis. A history review was only positive for mild back pain. Therefore lumbar-MRI with contrast was performed, revealing myositis of the right iliopsoas, gluteus-medius and paraspinal muscles with anterior muscle abscess. She underwent percutaneous abscess drainage and finished 4 weeks of oxacillin. She had a favorable outcome. Discussion Pyomyositis has 3 clinical stages and \u3e90% presents on stage 2. Progression to stage 3 can cause osteomyelitis, endocarditis, rhabdomyolysis, septic emboli and/or shock. Mortality is high as 10%. Predisposing factors such as HIV, malignancy and injection-drug-use should be mitigated. Athletes are predisposed to minor muscle injury that increases muscle perfusion and iron favoring bacterial growth. Delay in diagnosis is attributed to the deeply situated muscle but careful history, exam and appropriate imaging is the key