Evaluation of the MRSA/SA ELITe MGB assay for the detection of Staphylococcus aureus in bone and joint infections

Bone and joints infections represent a potentially devastating complication of prosthetic orthopaedic joint replacement, thus requiring both rapid and appropriate antibiotic treatment. Staphylococcus aureus is one of the most frequent pathogens involved in this pathology. Being able to assert its presence is the first step of patients’ efficient management. This monocenter study was aimed at evaluating the MRSA/SA ELITe MGB assay for the molecular detection of S. aureus and methicillin-resistant S. aureus (MRSAin bone and joint biopsies and synovial fluids. This test together with conventional techniques including standard cultures and 16S rRNA amplification assay were performed on 208 successive perioperative samples collected prospectively for one year from 129 patients. Using conventional techniques, a microbial pathogen was detected in 76 samples from 58 patients, out of which 40 were identified as S. aureus . The limit of detection (LODof the MRSA/SA ELITe MGB assay was experimentally determined for bone and joint biopsies and synovial fluids using negative samples spiked with S. aureus ATCC43300. The sensitivity of S. aureus detection with the MRSA/SA ELITe MGB assay was 82.5% (33/40 samplesand 97.5% (39/40 samplesusing manufacturer’s LOD and experimentally determined LOD respectively. Interestingly using the osteo-articular specific LOD, 15 additional samples were detected positive for S. aureus DNA with the MRSA/SA ELITe MGB assay; in all cases, those samples were taken from patients considered to be infected with S. aureus according to their clinical and microbiological records. The results were available within 24h, which could help to shorten the therapeutic decisions.