title: Comparison of the BD MAX MRSA XT to the Cepheid™ Xpert® MRSA assay for the molecular detection of methicillin-resistant Staphylococcus aureus from nasal swabs.
abstract: BACKGROUND
  Variation in MRSA genotypes may affect the sensitivity of molecular assays to detect this organism.
  
  
  METHODS
  We compared 2 commonly used screening assays, the Cepheid™ Xpert® MRSA and the BD MAX™ MRSA XT on consecutively obtained nasal swabs from 479 subjects. Specimens giving discordant results were subjected to additional microbiologic and molecular testing.
  
  
  RESULTS
  Six hundred forty-two (97.6%) of the 658 test results were concordant. Of the 16 discordant results from 12 subjects, additional results suggested that 9 (60%) of the 15 MRSA XT assays were likely correct, and 6 (40%) of the 15 Xpert® assays were likely correct. One discordant result could not be resolved. A mecA dropout and novel mec right-extremity junction (MREJ) sites led to false-positive and negative results by Xpert®.
  
  
  CONCLUSIONS
  While both assays performed well, continued vigilance is needed to monitor for Staphylococcus aureus with novel MREJ sites, mecA dropouts, and mecC, leading to inaccurate results in screening assays.
authors.affiliation: Department of Pathology, San Diego Veterans Affairs Medical Center, San Diego, CA, USA; Division of Infectious Diseases, University of California, San Diego, CA, USA. Electronic address: srmehta@ucsd.edu.
authors.forename: Sanjay R
authors.initials: SR
authors.lastname: Mehta
authors.affiliation: Department of Pathology, San Diego Veterans Affairs Medical Center, San Diego, CA, USA.
authors.forename: Jasmine
authors.initials: J
authors.lastname: Estrada
authors.affiliation: Department of Pathology, San Diego Veterans Affairs Medical Center, San Diego, CA, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Ybarra
authors.affiliation: Department of Pathology, San Diego Veterans Affairs Medical Center, San Diego, CA, USA; Division of Infectious Diseases, University of California, San Diego, CA, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Fierer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001431:Bacteriological Techniques / Q000379:methods*; D001681:Biological Assay / Q000379:methods*; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification*; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009666:Nose / Q000382:microbiology*; D012680:Sensitivity and Specificity; D013203:Staphylococcal Infections / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins
keywords: MREJ; MRSA; Molecular; Screening; mecA dropout; mecC