1009. Documenting the Sensitivity and Specificity of the new Roche LightCyclerŽ MRSA Advanced Test on Nasal Samples from the NorthShore MRSA Program
Session: Poster Abstract Session: Detecting, Identifying, and Typing Bacteria
Saturday, October 22, 2011
Room: Poster Hall B1
Background: 

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a major focus worldwide.  Real-time PCR (rtPCR) is emerging as the optimal diagnostic test for detection of MRSA colonization in the clinical laboratory.  The Roche LightCycler® MRSA Advanced test has been reported to be as sensitive and rapid as the GeneOhm assay, and that it had superior specificity.  To confirm these findings in a large MRSA control program setting, we performed the Roche LightCycler® MRSA Advanced test on nasal swab samples.

Methods: 

Discharge nasal swabs were collected from all inpatients at one of our facilities using a double-headed swab.  One nasal swab was plated onto CHROMagarTM MRSA (CM), (BBL, Becton Dickinson, Sparks, MD) then the same swab was broken off into Tryptic soy broth (TSB) for enrichment.  TSB was incubated for 24 hours then plated to CM.  Plates were incubated at 33-35 °C for 48 hours before finalizing a negative result.  After 24 hours the plate was examined, mauve colonies were subcultured to a blood agar plate (BBL, Becton Dickinson) and incubated for 24 hours.  S. aureus identification was confirmed on pure colonies by performing a Staphaurex agglutination test (Remel, Lenexa, KS).  The Roche LightCycler® MRSA Advanced test was performed on the second swab, according to the manufacturer’s instructions.  Clinical data and repeat testing was performed on discordant specimens to resolve discrepancies between culture and PCR.

Results: 

Any positive culture and history of prior MRSA were considered a gold standard (true positive) for this evaluation.  A total of 5,847 specimens were enrolled, 9 specimens could not be evaluated on the Roche LightCycler® test and hence were excluded.  For 5,838 specimens, the sensitivity, specificity, PPV and NPV of the Roche assay were 98.3% (95% CI: 96.3% to 99.2%), 98.9% (95% CI: 98.6% to 99.1%), 86.7% and 99.9% respectively.  Sensitivity of direct culture compared to the true positive was 58.7%, which increased to 67% when broth enrichment results were included.

Conclusion: 

Our results suggest that the Roche LightCycler® MRSA Advanced test has excellent sensitivity and specificity when used in a large MRSA control program.

 


Subject Category: N. Hospital-acquired and surgical infections, infection control, and health outcomes including general public health and health services research

Parul Patel, BS MT(ASCP), Payal Nagwekar, Donna Hacek, Kari Peterson, Althea Grayes and Lance Peterson, MD, NorthShore University HealthSystem, Evanston, IL

Disclosures:

P. Patel, None

P. Nagwekar, None

D. Hacek, None

K. Peterson, None

A. Grayes, None

L. Peterson, Roche: Consultant, Grant Investigator and Investigator, Consulting fee, Research grant and Speaker honorarium
BD GEneOhm: Consultant, Grant Investigator and Investigator, Grant recipient, Research grant and Speaker honorarium
Cepheid: Consultant, Grant Investigator and Investigator, Consulting fee, Grant recipient and Research grant
Syntezza: Grant Investigator and Investigator, Research grant
MicroPhage: Grant Investigator and Investigator, Grant recipient and Research grant
NanoSphere: Grant Investigator and Investigator, Grant recipient and Research grant

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.