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Diagn Microbiol Infect Dis. 2017 Apr;87(4):308-310. doi: 10.1016/j.diagmicrobio.2016.12.011. Epub 2016 Dec 16.

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.

Author information

1
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.
2
Department of Pathology, San Diego Veterans Affairs Medical Center, San Diego, CA, USA.
3
Department of Pathology, San Diego Veterans Affairs Medical Center, San Diego, CA, USA; Division of Infectious Diseases, University of California, San Diego, CA, USA.

Abstract

INTRODUCTION:

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®.

CONCLUSION:

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.

KEYWORDS:

MREJ; MRSA; Molecular; Screening; mecA dropout; mecC

[Indexed for MEDLINE]

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