Evaluation of the Verigene® Blood Culture Nucleic Acid test for rapid identification of gram positive pathogens from positive blood cultures

Background. The rapid identification of the etiology and the evaluation of the antimicrobial susceptibility of the bacteria causing bacteremia is of outmost relevance to set up an adequate treatment of sepsis. In this study we evaluated the microarray based method, Verigene Gram-positive blood cultures (BC-GP) nucleic acid test (Nanosphere Inc., Northbrook, IL, USA) for the identification of Gram positive pathogens from positive blood cultures. The panel BC-GP is capable to identify 13 germs and 3 genes associated with antimicrobial resistance.
Materials and Methods. In this study a total of 100 positive, non replicated and monomicrobic blood cultures have been evaluated. For testing on the Verigene platform using the BC-GP assay, 350 L of blood culture media from a positive the blood culture bottle.
Results. A total of 100 positive blood cultures were tested by the Verigene BC-GP assay: out of these a total of 100 Gram-positive cocci were identified. The most frequent bacteria identified included staphylococci, streptococci and enterococci. Among staphylococci, Staphylococcus aureus accounted for 25% (15/60), with 38% of S. epidermidis 37% (23/60) and 37% (22/60) other CoNS. All the S. aureus isolates were correctly identified by BC-GP whereas in 2/45 cases (4%) BC-GP misidentified CoNS. In the case of enterococci 7/10 were E. faecalis and 3 E. faecium, all of these were correctly identified.
Conclusions. The overall agreement with the results obtained by standard procedure is quite elevated (88%) and as a consequence the BC-GP panel could be used as a rapid diagnostic tool to give a faster response in the case of bacteremia associated with sepsis.