title: Comparison of the next-generation Xpert MRSA/SA BC assay and the GeneOhm StaphSR assay to routine culture for identification of Staphylococcus aureus and methicillin-resistant S. aureus in positive-blood-culture broths.
abstract: A bloodstream infection with Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), is a serious condition that carries a high mortality rate and is also associated with significant hospital costs. The rapid and accurate identification and differentiation of methicillin-susceptible S. aureus (MSSA) and MRSA directly from positive blood cultures has demonstrated benefits in both patient outcome and cost-of-care metrics. We compare the next-generation Xpert MRSA/SA BC (Xpert) assay to the GeneOhm StaphSR (GeneOhm) assay for the identification and detection of S. aureus and methicillin resistance in prospectively collected blood culture broths containing Gram-positive cocci. All results were compared to routine bacterial culture as the gold standard. Across 8 collection and test sites, the Xpert assay demonstrated a sensitivity of 99.6% (range, 96.4% to 100%) and a specificity of 99.5% (range, 98.0% to 100%) for identifying S. aureus, as well as a sensitivity of 98.1% (range, 87.5% to 100%) and a specificity of 99.6% (range, 98.3% to 100%) for identifying MRSA. In comparison, the GeneOhm assay demonstrated a sensitivity of 99.2% (range, 95.2% to 100%) and a specificity of 96.5% (range, 89.2% to 100%) for identifying S. aureus, as well as a sensitivity of 94.3% (range, 87.5% to 100%) and a specificity of 97.8% (range, 96.1% to 100%) for identifying MRSA. Five of six cultures falsely reported as negative for MRSA by the GeneOhm assay were correctly identified as positive by the Xpert assay, while one culture falsely reported as negative for MRSA by the Xpert assay was correctly reported as positive by the GeneOhm assay.
authors.affiliation: Medical College of Wisconsin, Milwaukee, Wisconsin, USA Dynacare Laboratories, Milwaukee, Wisconsin, USA.
authors.forename: Blake W
authors.initials: BW
authors.lastname: Buchan
authors.affiliation: Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Allen
authors.affiliation: Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Carey-Ann D
authors.identifier: http://orcid.org/0000-0002-1137-840X
authors.initials: CA
authors.lastname: Burnham
authors.affiliation: Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Erin
authors.initials: E
authors.lastname: McElvania TeKippe
authors.affiliation: Wishard Memorial Hospital, Indianapolis, Indiana, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Davis
authors.affiliation: Montefiore Medical Center, Bronx, New York, New York, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Levi
authors.affiliation: Sacred Heart Hospital, Pensacola, Florida, USA.
authors.forename: Donna
authors.initials: D
authors.lastname: Mayne
authors.affiliation: The Ohio State University Wexner Medical Center, Columbus, Ohio, USA.
authors.forename: Preeti
authors.initials: P
authors.lastname: Pancholi
authors.affiliation: Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Ryan F
authors.initials: RF
authors.lastname: Relich
authors.affiliation: NorthShore University HealthSystem, Evanston, Illinois, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Thomson
authors.affiliation: Medical College of Wisconsin, Milwaukee, Wisconsin, USA Dynacare Laboratories, Milwaukee, Wisconsin, USA nledeboe@mcw.edu.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Ledeboer
mesh_terms: D000293:Adolescent; D000328:Adult; D016470:Bacteremia / Q000175:diagnosis* / Q000382:microbiology; D001431:Bacteriological Techniques / Q000379:methods*; D001769:Blood / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D016106:Methicillin Resistance; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*