An Unusual Presentation of Disseminated Staphylococcus aureus Infection: Septic Arthritis and Massive Pleural Empyema.

Abstract

We report the case of a 56-year-old male who presented to the emergency department with a 10-day history of fever, chills, generalized weakness, and reduced appetite, followed by severe left knee pain and swelling and progressively worsening shortness of breath. The knee pain became severe enough to prevent weight bearing, while his respiratory symptoms progressed to breathlessness at rest. On presentation, he was febrile, tachycardic, tachypneic, and mildly hypoxemic. Examination revealed a markedly swollen, erythematous, warm, and tender left knee with severe pain on movement, together with markedly reduced air entry over the left lower and middle lung fields. Initial investigations demonstrated significant leukocytosis and markedly elevated inflammatory markers. Chest radiography showed a massive left sided pleural effusion with compressive change in the adjacent lung. Blood cultures subsequently grew methicillin susceptible Staphylococcus aureus. Aspiration of the left knee produced purulent fluid, with synovial fluid culture growing the same organism. Computed tomography of the chest demonstrated a large loculated left sided pleural collection with pleural thickening. Pleural fluid was purulent and also grew methicillin susceptible S. aureus, confirming empyema. Echocardiographic assessment did not demonstrate definite infective endocarditis. The patient was initially treated with empirical intravenous antibiotics, which were subsequently narrowed to intravenous cefazolin after susceptibility results became available. The infected knee was managed with arthroscopic washout and drainage. The large pleural empyema required image guided chest tube drainage, followed by intrapleural tissue plasminogen activator and DNase for residual loculated fluid. Serial blood cultures were initially positive but became negative following source control, with subsequent improvement in fever, respiratory symptoms, inflammatory markers, and knee function. This case highlights an unusual presentation of disseminated S. aureus infection involving simultaneous septic arthritis and massive pleural empyema. It emphasizes the importance of searching for metastatic infection when S. aureus is isolated from blood, particularly in patients with persistent bacteremia or symptoms involving multiple organ systems. Early microbiological diagnosis, appropriate imaging, repeated blood cultures, effective source control, and multidisciplinary management are essential in complicated S. aureus infection.