Interest of real-time PCR Xpert MRSA/SA on GeneXpert® DX System in the investigation of staphylococcal bacteremia | Intérêt de la PCR temps réel Cepheid Xpert SAMR/SA sur GeneXpert® DX System dans la prise en charge de la bactériémie à staphylocoque

AIM OF THE STUDY: Recently, a rapid, fully automated real-time PCR test has become available for detection of Staphylococcus aureus in positive blood cultures, Xpert MRSA/SA blood culture. This study was defined to evaluate the use of this product in our hospital setting to assist in optimizing antibiotic treatment. MATERIALS AND METHODS: Over a period of 18months (from February 2008 to July 2009), 51 positive blood cultures were examined for Staphylococcus using the Xpert MRSA/SA assay on the GeneXpert® System. The PCR results were transferred to the clinician as soon as available. The presence of empirical antibiotic therapy was noted and modified if necessary after discussions between the clinician and the infectious disease specialist. RESULTS: Twenty-three blood bottles were positive for S. aureus, two were resistant to methicillin. Twenty-eight were coagulase negative staphylococci. No discrepancy between identification (S. aureus) and methicillin resistance was observed. Thirty-two samples had clinically significant bacteremia (23 S. aureus and nine coagulase negative staphylococci). Sixteen (50%) of these patients had received inappropriate antibiotic therapy (11 without antibiotic therapy, five with betalactam antibiotics). For these patients, an appropriate antibiotic therapy was prescribed according to these results. Sixteen patients had adequate empirical antibiotic therapy at the time of receiving the PCR result. Among these 16 patients, eight switches were performed from broad-spectrum treatment to a more restrictive antistaphylococcal treatment. Of the 19 patients with a nonclinically relevant coagulase negative staphylococci infection, four were already on antibiotics for other infections and these treatments were not modified. Empirical treatment could be avoided in 13 patients who had a clinical presentation consistent with staphylococcal bacteremia (multiple sores, history of carrying methicllin-resistant or susceptible S. aureus infection, presence of intravascular material or prosthesis). CONCLUSION: The real-time PCR Cepheid Xpert MRSA/SA on GeneXpert® DX System has become an essential tool in our laboratory enhancing the reports of positive blood cultures for staphylococci. This test is fast (50min) and reliable. It allows optimization of antibiotic therapy in hospital.