Evaluation of the IDI-MRSA assay for detection of methicillin-resistant Staphylococcus aureus from clinical specimens

Abstract number: 1733_404

Lucke K., Hombach M., Pfyffer G.E.

Persistent spread of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals and other healthcare facilities requires suitable and efficient infection control strategies. Early detection of MRSA carriers and the rapid availability of diagnostic results are paramount for the implementation of efficient control measures. To determine the benefit of a recently developed molecular technique 691 high risk patients were screened for carriage of MRSA by real time PCR using the commercially available IDI-MRSA assay (GenOhm, San Diego, CA). Its efficacy as a screening test was assessed by analysing nasal, inguinal, rectal, and vaginal swabs as well as swabs from axilla, wound and throat. In addition, backup cultures for all specimens were done in parallel. Thirty-two of 691 specimens were both PCR and culture positive, while 633 specimens were negative with both methods. Sixteen specimens were PCR positive but culture negative, whereas 8 specimens were PCR negative but culture positive. For two specimens the PCR reaction was inhibited. Among the 16 specimens with a false susceptible PCR result 10 contained a methicillin-susceptible Staphylococcus aureus strain, but no MRSA. Overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the IDI-MRSA assay were 80.0%, 97.5%, 66.6%, and 98.8%, respectively.

In addition, our study demonstrates that the test is also applicable for specimens other than nasal swabs. With its excellent NPV the IDI-MRSA is a perfect screening test for a rapid exclusion of MRSA carriers. However, due to the incidence of false positive results we strongly recommend backup cultures. Taking into account the high cost for patient isolation and other infection control measures and in particular, the prevention of pathogen transmission within the hospital the expenses for the IDI-MRSA assay are more than paid off.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
Back to top