Evaluation of a novel optical assay for rapid detection of methicillin-resistant Staphylococcus aureus in liquid culture.

Valid detection of methicillin-resistant Staphylococcus aureus (MRSA) is a precondition for MRSA prevention measures. Most of the available MRSA screening tests are based either on the identification of colony material grown on solid agar media or on direct molecular approaches. The HB&L MRSA KIT (Alifax, Polverara, Italy) is designed to screen for MRSA in liquid cultures applying the light scattering technology. Here, the assay was evaluated with pure culture isolates from solid agar media on a representative subset of 29 MRSA and 171 methicillin-susceptible S. aureus clinical strains from a German multicenter study reflecting the ratio of MRSA to MSSA in Germany. Additionally, 53 mecA/mecC-MRSA comprising hospital-, community and livestock-associated MRSA as well as 20 clinical coagulase-negative staphylococci (CoNS) challenge strains were tested. Including the results of the assay-immanent confirmatory tests for positively tested strains, the sensitivity, specificity and the positive and negative predictive values were 100%. The methicillin-resistance was also correctly identified for all challenge strains.