The ability of a rapid PCR-based method to identify surgical patients colonised with methicillin-resistant Staphylococcus aureus

Abstract number: 1733_406

Hardy K.J., Gossain S., McMurray C., Shabir S., Alobwede I., Williams A., Athamneh N., Hawkey P.M.

Objectives: To determine the ability of the rapid IDI MRSA PCR based assay to identify surgical patients colonised with MRSA compared to conventional culture methods.

Methods: During a 9 month period all patients admitted to 4 surgical wards had nasal swabs taken for detection of MRSA on admission and every 4 days subsequently. Each swab was plated directly onto MRSA ID agar and then tested using the IDI MRSA assay. Additionally all swabs were placed in brain heart infusion broth incubated overnight and subcultured onto MRSA ID and Baird Parker agar for detection of MRSA and MSSA respectively.

Results: A total of 7545 nasal samples were examined from 3769 patients. Seven hundred and fifty six samples were positive by the IDI MRSA assay, of which MRSA was isolated on direct culture from 374 (49.5%). Of the 382 samples that were negative on direct culture, MRSA was isolated on broth enrichment from 138 samples, and MSSA from 42 samples. Of the 244 samples that were IDI MRSA assay positive but did not have MRSA isolated, 77 (31.6%) came from patients that had previous or subsequent samples from which MRSA was isolated. When individual patients are examined a total of 465 of the 3769 patients (12.3%) sampled had at least one sample that was positive by the IDI MRSA assay, of which 254 (54.6%) were positive by direct culture. An additional 76 patients had MRSA isolated from broth enrichment, but a total of 135 patients (29%) were only ever found to be positive by the IDI MRSA assay and did not have MRSA isolated using culture. Overall the IDI MRSA assay has a sensitivity of 97%, a specificity of 96.1%, NPV of 99.7% and a PPV of 71%.

Conclusion: The IDI MRSA assay provides a rapid and sensitive way of screening surgical patients for MRSA, with a very high negative predictive value. The increased number of patients identified as colonised with MRSA using the IDI MRSA assay compared to conventional culture, may be due to the increased sensitivity of PCR compared to culture. Rapid and sensitive identification of surgical patients colonised with MRSA aids in the prompt decolonisation and isolation of patients.

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:
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