Evaluation of the BD GeneOhm StaphSR assay for detection of Staphylococcus aureus in patients in intensive care units

Background: Staphylococcus aureus is the major nosocomial pathogen and rapid detection of colonized patients with subsequent precaution is needed to prevent transmission. A new assay, the BD GeneOhm™ SaphSR assay (BD GeneOhm™, San Diego, CA, USA), is a multiplex real-time polymerase chain reaction (PCR) for rapid detection of both methicillin-sensitive S aureus (MSSA) as well as methicillin-resistant S aureus (MRSA). Methods: Anterior nasal swab specimens of 273 pediatric and adult patients hospitalized in intensive care units at Chang Gung Memorial Hospital were collected for this assay in parallel with conventional cultures as standard. Results: Overall, 71 (26.0%) patients were colonized with S aureus by conventional culture and MRSA accounted for 67.6% of all isolates. For the detection of MRSA, 79 patients (28.9%) were positive by PCR and 48 (17.6%) were positive by conventional cultures. The sensitivity, specificity, and positive and negative predictive values were 95.9%, 85.3%, 58.5%, 99.0%, respectively. For the detection of MSSA, 48 patients (17.6%) were positive by PCR and 23 (8.4%) were positive by conventional culture. The sensitivity, specificity, and positive and negative predictive values were 91.3%, 89.2%, 43.8%, and 99.1%, respectively. Conclusion: As a screening method, the BD GeneOhm™ StaphSR assay could rapidly detect and differentiate between MRSA and MSSA colonization. A negative result of the assay could almost exclude S aureus colonization.