Intraoperative diagnosis of Staphylococcus aureus and coagulase-negative Staphylococcus using Xpert MRSA/SA SSTI assay in prosthetic joint infection

The aim of this prospective study was to evaluate the performance of the Polymerase Chain Reaction (PCR) tool Xpert MRSA/SA SSTI test (Cepheid, Sunnyvale, CA, USA) on periprosthetic samples from a cohort of patients with suspected prosthetic joint infection (PJI). Seventy adult patients were included in this prospective study. On the basis of the preoperative evaluation, 39 patients were clinically considered to have a PJI, whereas 31 were presumed to suffer from an aseptic mobilization of the implant. Xpert MRSA/SA SSTI identified 4 out of 4 MRSA, 7 out of 7 MSSA, and 14 out of 16 methicillin resistant CoNS. Among the 31 patients not having a PJI, the rapid PCR did not find any bacteria among those identifiable, thus demonstrating an excellent performance in terms of specificity. Statistical analysis of the analytical performance showed a high correlation (p<0.001) between the result of Xpert MRSA/SA SSTI and culture. Xpert MRSA/SA SSTI assay is a novel, yet well known, rapid and accurate method for the identification of different species of staphylococci. The test can be used with peri-operative samples thus dramatically improving the diagnostic sensitivity. In addition, thanks to the very short turnaround time the use of Xpert assay can modify the clinical management of patients suffering from PJI during the ongoing operative procedure.