Impact of reduced vancomycin susceptibility on the therapeutic outcome of MRSA bloodstream infections

Abstract

Background: The aim of this study was to determine whether clinical outcome of patients with methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia was correlated with vancomycin susceptibility of the corresponding strains. Methods: A retrospective study on MRSA bacteraemia was performed at a teaching hospital between January 1998 and October 2005 by linking vancomycin susceptibility profiles of patients' isolates with hospitalization data. Results: A total of 20 out of 209 MRSA bacteraemia patients were treated with vancomycin for at least 5 days with adequate trough levels, and fulfilled the study's inclusion and exclusion criteria. Twenty-two S. aureus isolates from these patients' blood cultures were identified as MRSA, including two hetero-VISA from separate patients and two VISA with vancomycin MIC of 4 mg/L from one patient. Between patients who showed 'good' vancomycin response and patients who did not, there was a significant difference (p < 0.01) in their corresponding MRSAs' vancomycin susceptibility expressed by 'area under curve' (AUC) of population analysis. Significant correlations were found between AUC and initial vancomycin therapeutic response parameters of 'days till a febrile' (r = 0.828, p < 0.01) and 'days till CRP ≤ 30% of maximum' (r = 0.627, p < 0.01) Conclusion: Our study results cautionhealthcare personnel that early consideration should be given to cases with a poor vancomycin treatment response that could signify the involvement of MRSA with reduced susceptibility to vancomycin. © 2007 Neoh et al; licensee BioMed Central Ltd.