For in vitro diagnostic use. Others cobas MRSA SA Test IVD cobas® MRSA/SA Test RMD-4800-MRSASA-001 for use on the cobas® 4800 System 06768113190 KIT COBAS 4800 MRSA/SA AMP/DET 80T IVD cobas MRSA/SA Test 00875197004410 Reagents, kits 1 kit 80 tests true 06768172190 KIT COBAS 4800 MRSA/SA AMP/DET 240T IVD cobas MRSA/SA Test 00875197004427 Reagents, kits 1 kit 240 tests true The cobas® MRSA/SA Test on the cobas® 4800 System, is a qualitative in vitro diagnostic real-time PCR assay, for the direct detection of methicillin-resistant Staphylococcus aureus (MRSA) and S.aureus (SA) DNA from nasal swabs to aid in the prevention and control of MRSA and SA infections in healthcare settings. The cobas® MRSA/SA Test is not intended to diagnose, guide or monitor treatment for MRSA or SA infections, or provide results of susceptibility to methicillin. A negative result does not preclude MRSA/SA nasal colonization. Concomitant cultures are necessary to recover organisms for epidemiology typing or for further susceptibility testing. en Sample preparation Sample preparation for the cobas® MRSA/SA Test is automated with the use of the cobas® x 480 instrument. Organisms are lysed with chaotropic agent, proteinase K, and SDS reagents. Released nucleic acids, along with added Internal Control DNA, are bound by magnetic glass particles. They are washed and then eluted into a small volume of buffer. The instrument then takes an aliquot of the eluted material and sets up the PCR reaction with an activated Master Mix. PCR amplification and TaqMan® detection The PCR cycling steps and detection of target signal occurs in the cobas® z 480 analyzer. The Master Mix reagent contains primer pairs and probes for three targets: the SCCmec cassette Right Extremity junction region which is specific to MRSA, a genomic target for all SA (including MRSA), and Internal Control. If the target nucleic acid sequences are present, amplification with the corresponding primers will occur by a thermostable DNA polymerase, generating PCR products (amplicon). These products are detected by specific TaqMan probes containing a fluorescent dye and a quencher. Normally, the quencher suppresses the fluorescence of the dye. However, if the PCR product is present, the probe hybridizes to the product and gets cleaved by the 5’ to 3’ nuclease activity of the polymerase. This reaction allows the fluorescence to be emitted from the dye, and the signal is recorded in real time during each PCR cycle by the cobas® z 480 analyzer. The signal is interpreted by the cobas® 4800 System Software and reported as final results. Selective amplification Selective amplification of target nucleic acid from the specimen is achieved in the cobas® MRSA/SA Test by the use of AmpErase (uracil-N-glycosylase) enzyme and deoxyuridine triphosphate (dUTP). The AmpErase enzyme recognizes and catalyzes the destruction of DNA strands containing deoxyuridine11, but not DNA containing deoxythymidine. Deoxyuridine is not present in naturally occurring DNA, but is always present in amplicon due to the use of deoxyuridine triphosphate in place of thymidine triphosphate as one of the dNTPs in the Master Mix reagent; therefore, only amplicon contain deoxyuridine. Deoxyuridine renders contaminating amplicon susceptible to destruction by AmpErase enzyme prior to amplification of the target DNA. AmpErase enzyme, which is included in the Master Mix reagent, catalyzes the cleavage of deoxyuridine-containing DNA at the deoxyuridine residues by opening the deoxyribose chain at the C1position. When heated in the first thermal cycling step at the alkaline pH of Master Mix, the amplicon DNA chain breaks at the position of the deoxyuridine, thereby rendering the DNA non-amplifiable. AmpErase enzyme is inactive at temperatures above 55ºC, i.e., throughout the thermal cycling steps, and therefore does not destroy target amplicon. The cobas® MRSA/SA Test has been demonstrated to inactivate at least 103 copies of deoxyuridine-containing MRSA/SA amplicon per PCR. 11. Hardy K, Price C, Szczepura A, et al. Reduction in the rate of methicillin-resistant Staphylococcus aureus acquisition in surgical wards by rapid screening for colonization: a prospective, cross-over study. Clin Microbiol Infect. 2010;16(4):333-339. Epub 2009/07/23. en