Genexpert dx system v4.7b

The GeneXpert^® PA assay (Cepheid, USA) is a PCR test that is currently available for research use. The assay was performed according to the manufacturer's instructions. Briefly, ETA samples were adsorbed onto a Cepheid collection device swab (CLASSIQ, COPAN), dissolved in elution buffer and vortexed at high speed for 10 s (Scientific Industries Inc., USA). From the elution reagent, 1.7 ml was transferred to the cartridge and analysed by GeneXpert^® Dx system v4.7b (Cepheid, USA). The overall process of extraction, amplification, and detection of intact bacterial cells was completed in 55 min. Samples were reported by the accompanied GeneXpert software as either P. aeruginosa “detected” or “not detected”. The detection was based on the P. aeruginosa PCR cycle threshold (Ct) values and the Ct values of the sample adequacy control (a multiplexed control that contains primers and probes for the detection of human cells or DNA and should only be considerd in case of a P. aeruginosa-negative result) and sample processing control (a control containing Bacillus globigii spores for verification of successful bacterial cell lysis) with valid Ct ranges between 3 and 45 for all three targets.

The GeneXpert assay is currently available for research (RMRSA/SA-ETA-10, Cepheid, USA) and was performed according to manufacturer’s instructions. Briefly, ETA samples were adsorbed onto a Cepheid collection device swab (COPAN- 900-0370, USA), dissolved in elution buffer and vortexed at high speed for 10 s (Scientific Industries Inc., USA). The entire content of the elution reagent was transferred to the cartridge and analysed by GeneXpert® Dx system v4.7b (Cepheid, USA). The overall process of extraction, amplification, and detection of the targets was completed in 66 min. The primers and probes in the MRSA/SA ETA assay detect sequences within the staphylococcal protein A (spa) gene, the methicillin resistance gene (mecA), and the staphylococcal cassette chromosome (SCCmec) inserted into the S. aureus chromosomal attB insertion site [9 ]. Samples were reported by GeneXpert as either S. aureus “detected” (Ct 3–36) or “not detected”.