Detection of methicillin-resistant Staphylococcus aureus directly from nasal swab specimens by a real-time PCR assay.
Screening for colonization with methicillin-resistant Staphylococcus aureus (MRSA) is a key aspect of infection control to limit the nosocomial spread of this organism. Current methods for the detection of MRSA in clinical microbiology laboratories, including molecularly based techniques, require a culture step and the isolation of pure colonies that result in a minimum of 20 to 24 h until a result is known. We describe a qualitative in vitro diagnostic test for the rapid detection of MRSA directly from nasal swab specimens (IDI-MRSA; Infectio Diagnostic, Inc., Sainte-Foy, Quebec, Canada), based upon a real-time PCR and direct detection of MRSA via amplicon hybridization with a fluorogenic target-specific molecular beacon probe. Samples from 288 patients were analyzed for the presence of MRSA with the IDI-MRSA assay, compared to detection by either direct plating or enrichment broth selective culture methods. The diagnostic values for this MRSA screening method were 91.7% sensitivity, 93.5% specificity, 82.5% positive predictive value, and 97.1% negative predictive value when compared to culture-based methods. The time from the start of processing of specimen to result was approximately 1.5 h. In our hands, the IDI-MRSA assay is a sensitive and specific test for detection of nasal colonization with MRSA and providing for same-day results, allowing more efficient and effective use of infection control resources to control MRSA in health care facilities.
Warren
David K
DK
Division of Infectious Diseases, Washington University School of Medicine, Campus Box 8051, 660 S. Euclid Ave., Saint Louis, MO 63110, USA. dwarren@wustl.edu
Liao
Robert S
RS
Merz
Liana R
LR
Eveland
Michael
M
Dunne
W Michael
WM
D003470:Culture Media; D006801:Humans; D016106:Methicillin Resistance; D009666:Nose / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods*; D011237:Predictive Value of Tests; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D013997:Time Factors
D003470:Culture Media; D011933:Reagent Kits, Diagnostic