[Performance evaluation of BD GeneOhm MRSA PCR assay for detection of nasal colonization of methicillin-resistant Staphylococcus aureus at endemic intensive care units].
BACKGROUND
The BD GeneOhm MRSA PCR assay (Becton Dickinson, USA) is a qualitative real-time PCR test for rapid detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA). We evaluated the performance of BD GeneOhm MRSA PCR assay versus MRSASelect (Bio-Rad, France) and broth enrichment cultures for detection of MRSA from nasal swabs.


METHODS
From August 2008 to January 2009, 295 nasal swabs were taken from patients in intensive care units and transported to the laboratory with BD CultureSwab Liquid Stuart Single Swab (Becton Dickinson, USA). The swabs were inoculated onto MRSASelect first and then suspended into GeneOhm sample buffer: 100 microL of the suspension was inoculated into 6.5% NaCl-tryptic soy broth (Becton Dickinson, USA), which was subcultured on MRSASelect after overnight incubation (TSBS). Performances of GeneOhm MRSA and MRSASelect were compared to TSBS.


RESULTS
With GeneOhm MRSA, 125 swabs (44.6%) were positive for MRSA, 13 (4.4%) were unresolved, and 2 were not determined. With MRSASelect and TSBS 86 (29.4%) and 106 swabs (36.2%), respectively, were positive. The sensitivity, specificity, and positive and negative predictive value of GeneOhm MRSA were 85.8%, 77.5%, and 72.8% and 93.5%, respectively, and corresponding values for MRSASelect were 78.3%, 94.8%, and 96.5% and 88.9%. Of the 33 patients whose 34 specimens were found false positive in GeneOhm MRSA, 23 patients were MRSA-positive either previously or subsequently to this study. All of the 10 patients with false-negative specimens in GeneOhm MRSA PCR assay were previously MRSA or methicilln-resistant coagulase negative staphylococci (MRCNS)-positive and were treated for MRSA, but they became MRSA-positive after 1 to 4 negative surveillance cultures.


CONCLUSIONS
GeneOhm MRSA PCR assay showed a relatively high negative predictive value. However, its low specificity and frequent occurrence of unresolved results would be problematic in the endemic areas with a high prevalence of MRSA.
Park
Sang Hyuk
SH
Department of Laboratory Medicine, University of Ulsan College of Medicine, Seoul, Korea.
Jang
Yoon Ha
YH
Sung
Heungsup
H
Kim
Mi Na
MN
Kim
Jae Suk
JS
Park
Yeon Joon
YJ
D019353:Endemic Diseases; D006801:Humans; D007362:Intensive Care Units; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification*; D009666:Nose / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods*; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000453:epidemiology
D011933:Reagent Kits, Diagnostic