SESSION TYPE: ICU Infections
PRESENTED ON: Wednesday, October 24, 2012 at 02:45 PM - 04:15 PM
PURPOSE: Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of severe infections with high rates of mortality. Although, several anti-MRSA antibiotics are now available, vancomycin represents the cornerstone of therapy for serious MRSA infections. Unfortunately increasing cases of therapeutic failures have been demonstrated. The aim of the study was to assess the distribution of vancomycin, daptomycin and linezolid minimum inhibitory concentrations (MICs) and to identify the clinical characteristics and outcomes of patients with severe MRSA infections.
METHODS: This retrospective cohort study involved adults admitted due to MRSA infections between March and November 2011 in a university-affiliated hospital Intensive Care Unit (ICU). We compared the MIC values obtained by automated microdilution with Vitek 2 (bio-Merieux, Durham, NC) with manual susceptibility system Etest (bio-Merieux, Durham, NC). A total of 16 patients with MRSA infection were admitted in ICU.
RESULTS: Mean age and Acute Physiological and Chronic Health Evaluation (APACHE) II score were 58.8 and 15.5, respectively. Vitek 2 revealed a geometric mean MIC of 0.67 mg/mL for vancomycin, 0.3 mg/ml for daptomycin and 1.8 mg/ml for linezolid, respectively. While Etest demonstrated geometric mean MIC of 2.0 mg/mL for vancomycin, 0.67 mg/mL for daptomycin and 1.61 mg/ml for linezolid. Vancomycin was chosen as initial antibiotic in 10 out of 16 patients (62.5%). Of those, mean length of hospitalization was 12.7 days, 40% (4/10) of patients expired, 6 patients (60%) required prolong hospitalization including transfer to university hospital for cardio-thoracic surgery and/or to nursing home to complete their antibiotic treatment.
CONCLUSIONS: Our results demonstrate that vancomycin and daptomycin MICs obtained by Etest were consistently higher than values generated by Vitek2 (p: < 0.0001 and p 0.002, respectively). As consequence, we noticed a prolonged length of hospitalization and high rate of treatment failures.
CLINICAL IMPLICATIONS: Thus, we suggest that Etest should be performed in patients presenting with severe MRSA infections to increase accuracy of determination of MIC values and reduce risk of treatment failure, mortality and cost of care.
DISCLOSURE: The following authors have nothing to disclose: Lorenzo Zaffiri, Rasha Abdulmassih, Shafik Boyaji, Ryan Bickel, Anita Charochak, Jeffrey Wilt, Paul Lange, Mark Loehrke, William Nichols
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