Potential Failure of Vancomycin Dosing Using AUC/MIC in a Patient With Purulent Methicillin-Resistant Staphylococcus aureus Pericarditis

Objective: The objective of this case report is to describe utilization of area under the curve (AUC)/minimum inhibitory concentration (MIC) vancomycin dosing with variable MIC results in a patient with methicillin-resistant Staphylococcus aureus (MRSA) purulent pericarditis. Case: A 57-year-old Caucasian male presented with cardiac tamponade and pulmonary emboli. Echocardiogram showed moderate-large pericardial effusion with signs of early tamponade physiology. Pericardiocentesis removed serosanguinous, straw yellow fluid. Blood and pericardial cultures revealed MRSA. Patient was then initiated on vancomycin with an initial AUC of 415. MIC of repeat blood cultures were inconsistent. After 8 days of persistent bacteremia, patient was transitioned to daptomycin and ceftaroline with blood culture clearance within 48 hours. Discussion/Conclusion: Guidelines recommend AUC/MIC vancomycin dosing in patients with MRSA bacteremia. Literature regarding treatment of MRSA purulent pericarditis is limited to case reports. Evidence shows variation in MIC results dependent on analysis methods. Further studies on obtaining accurate MIC values and use of AUC/MIC dosing for MRSA purulent pericarditis are prudent to provide appropriate therapy in these patients as mortality is high.