Rapid detection of meticillin-resistant and meticillin-susceptible Staphylococcus aureus by real-time PCR directly from positive blood culture bottles

Abstract number: P2127

Nonhoff C., Denis O., Hallin M., Pavlov S., Cuvelier S., Deplano A., Struelens M.J.

Background: Recently, a new automated system Xpert MRSA/SA assay (Cepheid, USA) has been developed for direct detection of Staphylococcus aureus and determination of meticillin resistance in clinical specimens. This real time PCR is a fully-automated molecular testing platform which combines sample preparation, multiplex PCR assay and nucleic acid analysis. The objective of this study was to evaluate the performance of the Xpert MRSA/MSSA assay directly from positive blood culture bottles.

Material: Real time PCR assays were prospectively performed directly on signal positive blood cultures (Bactec 9240, Beckon Dickinson, USA). 50 ml of blood culture broth were transferred into the elution reagent tube. The PCR assay was performed according to the manufacturer's instructions. Phenotypic identification and antibiotic susceptibility testing were performed in parallel. Suspected colonies of S. aureus were identified by latex slide agglutination and coagulase testing. Oxacillin susceptibility was tested by cefoxitin disk diffusion according to CLSI recommendations.

Results: A total of 197 signal positive blood cultures from 87 patients were tested by real time PCR. S. aureus isolates including 22 MRSA and 32 MSSA which were all correctly detected by Xpert assay. The sensitivity and specificity of PCR compared with phenotypic methods were both 100%. The PCR assay provided results in less than 2 hours versus 48 hours for conventional methods.

Conclusion: The Xpert MRSA/MSSA assay correctly detected 100% of MSSA and MRSA isolates from positive blood cultures in less than 2 hours. Prospective studies are needed to evaluate the clinical impact of this assay for rapid implementation of targeted treatment for S. aureus bacteraemia.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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