D-1138. Comparison of the GeneXpert Xpert MRSA Assay (GXP-MRSA), BD GeneOhm MRSA Assay (BD-MRSA) & Routine Culture for the Detection of Nasal & Cutaneous Colonisation with Methicillin-Resistant Staphylococcus aureus (MRSA)
Session: Poster Session: Staphylococcus aureus: Screening, Typing and Epidemiology
Sunday, October 26, 2008: 12:00 AM
Room: Hall C
Background: We have previously shown BD-MRSA (BD Diagnostics) to have excellent sensitivity/specificity when assessing combined nose/groin swabs (CNG) for MRSA colonization (J Clin Micro. 2006; 44:2904). However, the accuracy of GXP-MRSA (Cepheid) in this setting and comparisons between GXP-MRSA, BD-MRSA and chromogenic agar-based culture methods (CA) for detecting MRSA colonization are uncertain.
Methods: Concurrent assessment for nose/groin colonization by GXP-MRSA was undertaken on a group of patients known to be MRSA-colonized or non-colonized using single specimens from the nose (SN), groin (SG) and CNG. Following this validation, GXP-MRSA was prospectively compared to BD-MRSA and CA in a separate group of patients to accurately identify MRSA colonization using CNG swabs. Results: GXP-MRSA assessment of CNG was 100% concordant with results from SN and SG swabs and compared to CA was 89.5% (17/19) sensitive and 95% (19/20) specific. All 3 assays were assessed in 210 patients, of whom 46/210 (22%) were MRSA-colonized by CA. GXP-MRSA and BD-MRSA assays showed 94% (195/208) concordance, with 1% (2/210) specimens unresolved by GXP-MRSA due to inhibition. Compared to CA, GXP-MRSA and BD-MRSA had similar sensitivity (40/46 [87.0%] vs 39/46 [84.8%]) and specificity (152/162 [93.8%] vs 152/164 [92.7%]), respectively. Conclusions: GXP-MRSA assessment of CNG swabs is sensitive/specific compared to similar analyses of SN and SG swabs. GXP-MRSA and BD-MRSA have similar sensitivity and specificity for assessing nasal and cutaneous MRSA colonization using CNG specimens. The choice of which PCR assay is preferred can be based on other features, such as whether specimens can be batched or the technical expertise required for each assay.
Ben Howden, PhD1, Elizabeth Grabsch2, M Grayson2, Peter Kelley, MBBS3, Shar Ghaly-Derias2, Wei Gao, BS4 and  P. G. Kelley, None., (1)Infectious Diseases & Microbiol. Dept., Austin Health, (2)Austin Health, (3)Austin Health, Melbourne, Australia, (4)Montefiore Med Ctr, Bronx, NY