Streptococcus milleri infections of the pleural space: operative management predominates

Management of patients with thoracic empyema ranges from tube thoracostomy drainage, with or without fibrinolytics, to operative intervention, with the optimal intervention remaining uncertain. Streptococcus milleri, typically a benign bacterium colonizing the oropharynx, has recently been reported as a potential pathogen in pneumonia and pleural space disease. Our initial experience indicated this infection, when in the pleural space, was particularly tenacious and often required major operative intervention to eradicate. Therefore, we hypothesized that patients with S milleri pleural space infections often require operative intervention as definitive treatment.

We reviewed all patients from June 17, 1999 to April 15, 2005 with S milleri infections at our level I academic trauma/acute care surgery department at a safety-net hospital. S milleri infections were diagnosed by thoracentesis, bronchoalveolar lavage, tube thoracostomy fluid, or intraoperative culture.

Over the 70-month period evaluated, of 697 patients with S milleri infections, 39 patients had S milleri infections of the pleural space; 26 (67%) patients underwent operative intervention. The majority (72%) were men with a mean age of 46 (range 22 to 63); the underlying etiology in those patients requiring operation was pneumonia (26 patients; 67%), trauma (9 patients; 23%), postoperative infection (2 patients), foreign body ingestion (1 patient), and malignancy (1 patient). The vast majority of patients in the operative group were treated preoperatively with tube thoracostomy (88%) and antibiotics (96%). The average duration of chest tube drainage prior to operation was 4.4 days (95% confidence interval [CI] 2.6 to 6.2) and antibiotic treatment was 6.0 days (95% CI 3.8 to 8.2). Thirteen patients (50%) underwent video-assisted thoracoscopic surgery (VATS) and 13 patients required thoracotomy. VATS was performed more often when operative intervention occurred early (average hospital day 6.2) compared to initial thoracotomy or conversion from VATS to thoracotomy (average hospital day 9.8). Hospital length of stay was less in the operative group (average 24 days; 95% CI 17 to 31) than in the nonoperative group (34 days; 95% CI 19 to 49), discharge to home was greater in the operative group (77% vs. 16%), and mortality was less in operative group (0% vs. 23%).

Despite attempts at nonoperative management, the majority of patients with a S milleri pleural space infection require operative intervention for definitive therapy. Patients diagnosed with S milleri empyema should be considered for early operative intervention due to the unrelenting nature of their infection. Operative treatment is associated with a shorter hospital length of stay, increased discharge to home, and decreased mortality.