Clinical Characteristics and Risk Factors for Mortality in Patients with Meningitis Caused by Staphylococcus aureus and Vancomycin Minimal Inhibitory Concentrations Against These Isolates

Background/Purpose: Bacterial meningitis caused by Staphylococcus aureus is uncommon but has a high mortality rate. The aims of this study were to better understand the clinical manifestations of S. aureus meningitis, to identify the risk factors for mortality in the affected patients, and to determine the levels of vancomycin minimal inhibitory concentrations (MICs) against these pathogens. Methods: A retrospective study of patients with S. aureus meningitis hospitalized between December 2000 and December 2008 was made, and vancomycin MICs against S. aureus isolates was determined using Etest. Results: Among 37 patients with S. aureus meningitis, fever was most commonly observed. Twenty-six patients (70.3%) had received prior neurosurgery, and 24 (64.9%) patients were suffering from methicillin-resistant S. aureus (MRSA) infections. The vancomycin MIC of 2 μg/mL was found in 23 (74.2%) of 31 S. aureus isolates available for testing. Excluding three patients who did not receive antibiotics for their S. aureus meningitis the mortality rate was 35.3% in the 34 remaining patients, with concurrent infective endocarditis an independent risk factor for mortality (odds ratio = 21.00; 95% confidence interval, 1.834-240.515; p = 0.01). Conclusion: Patients with S. aureus meningitis and concurrent infective endocarditis were at a higher risk of mortality. A vancomycin MIC of 2 μg/mL against a substantial number of S. aureus isolates that grew from the cerebrospinal fluid suggests the importance of obtaining trough vancomycin concentrations of 15-20 μg/mL for the treatment of MRSA meningitis.