Implementation of a Rapid Microarray Assay for the Detection of Gram-Positive, Gram-Negative and Resistance Determinants： Assessing Performance in a Clinical Laboratory in Bulgaria

Two hundred and seven positive blood cultures from two blood culture systems (Bactec and BacTAlert) between May 2012 and February 2014 were enrolled in this study. We present the results of prospectively tested, non-duplicate Gram-positive and Gram-negative organisms tested by the BC-GP (Verigene® Gram-positive) and BC-GN (Gram-negative) Blood Culture Assays (Nanosphere, Inc.) for the first time in Bulgaria. These assays represent new tools for the rapid detection of pathogens and resistance markers in blood stream infections. Results of the Verigene System were compared with conventional testing methods. Of the 207 isolates, 180 (87.0%) were targets on the blood culture panels. Correct identification of Gram-positive organisms was 99.2% and of Gram-negative organisms was 98.2% for organisms that could be detected with BC-GP and BC-GN. Additionally, staphylococci tested for the presence of the mecA gene showed a 75.7% correlation with the cefoxitin test and identification of methicillin-resistance by Vitek 2. ESBLs (extended-spectrum beta-lactamases) for Gram-negative organisms were detected by both methods, showing 100% agreement.