Multiplex Identification of Gram-Positive Bacteria and Resistance Determinants Directly from Positive Blood Culture Broths: Evaluation of an Automated Microarray-Based Nucleic Acid Test

AbstractThe Verigene Gram-Positive Blood Culture (BC-GP) nucleic acid assay (Nanosphere, Inc., Northbrook, IL, USA) is a newly developed microarray-based test with which 12 Gram-positive bacterial genes and three resistance determinants can be detected using blood culture broths. We evaluated the performance of this assay and investigated the signal characteristics of the microarray images.At the evaluation stage, we tested 80 blood cultures that were positive for various bacteria (68 bacteria covered and 12 not covered by the BC-GP panel) collected from the blood of 36 patients and 44 spiked samples. In instances where the automated system failed and errors were called, we manually inspected microarray images, measured the signal intensities of target spots, and reclassified the results.With the manual analysis of the microarray images of 14 samples for which error calls were reported, we could obtain correct identification results for 12 samples without the need for retesting, because strong signals in the target spots were clearly discriminable from background noise. With our interpretation strategy, we could obtain 97.1% sensitivity and 100% specificity for bacterial identification by using the BC-GP assay. The two unidentified bacteria were viridans group streptococci, which produced weaker target signals. During the application stage, among 25 consecutive samples positive for Gram-positive bacteria, we identified two specimens with error calls asWith help of the manual review of the microarray images, the BC-GP assay could successfully identify species and resistance markers for many clinically important Gram-positive bacteria.

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

Microbiologia Medica ◽

10.4081/mm.2015.4945 ◽

2015 ◽

Vol 30 (1) ◽

Author(s):

Agnese Cellini ◽

Maria Federica Pedna ◽

Francesca Del Bianco ◽

Vittorio Sambri

Keyword(s):

Nucleic Acid ◽

Blood Culture ◽

Culture Media ◽

Rapid Identification ◽

Blood Cultures ◽

Gram Positive ◽

Adequate Treatment ◽

Culture Bottle ◽

Nucleic Acid Test ◽

Acid Test

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.

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Preliminary Evaluation of the Research-Use-Only (RUO) iCubate iC-GPC Assay for Identification of Select Gram-Positive Bacteria and Their Resistance Determinants in Blood Culture Broths: TABLE 1

Journal of Clinical Microbiology ◽

10.1128/jcm.01934-15 ◽

2015 ◽

Vol 53 (12) ◽

pp. 3931-3934 ◽

Cited By ~ 5

Author(s):

Blake W. Buchan ◽

Garrett C. Reymann ◽

Paul A. Granato ◽

Brenda R. Alkins ◽

Patricia Jim ◽

...

Keyword(s):

Blood Culture ◽

Staphylococcus Epidermidis ◽

Bacterial Species ◽

Genetic Resistance ◽

Preliminary Evaluation ◽

Gram Positive ◽

Content Type ◽

Gram Positive Bacteria ◽

Resistance Determinants ◽

On Demand

The iC-GPC assay (iCubate, Huntsville, AL) provides a molecular option for the rapid, on-demand analysis of positive blood cultures. A preliminary evaluation of the iC-GPC assay using 203 clinical or seeded specimens demonstrated a sensitivity of 93.8% to 100% and a specificity of 98.0% to 100% for the identification of five Gram-positive bacterial species (Staphylococcus aureus,Staphylococcus epidermidis,Streptococcus pneumoniae,Enterococcus faecalis, andEnterococcus faecium) and three associated genetic resistance determinants (mecA,vanA, andvanB) in positive blood culture broths.

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Rapid Testing Using the Verigene Gram-Negative Blood Culture Nucleic Acid Test in Combination with Antimicrobial Stewardship Intervention against Gram-Negative Bacteremia

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04259-14 ◽

2014 ◽

Vol 59 (3) ◽

pp. 1588-1595 ◽

Cited By ~ 51

Author(s):

Jacqueline T. Bork ◽

Surbhi Leekha ◽

Emily L. Heil ◽

LiCheng Zhao ◽

Rilwan Badamas ◽

...

Keyword(s):

Nucleic Acid ◽

Blood Culture ◽

Antibiotic Therapy ◽

Antimicrobial Stewardship ◽

Clinical Isolates ◽

Molecular Diagnostic ◽

Negative Blood Culture ◽

Gram Negative ◽

Nucleic Acid Test ◽

Acid Test

ABSTRACTRapid identification of microorganisms and antimicrobial resistance is paramount for targeted treatment in serious bloodstream infections (BSI). The Verigene Gram-negative blood culture nucleic acid test (BC-GN) is a multiplex, automated molecular diagnostic test for identification of eight Gram-negative (GN) organisms and resistance markers from blood culture with a turnaround time of approximately 2 h. Clinical isolates from adult patients at the University Maryland Medical Center with GN bacteremia from 1 January 2012 to 30 June 2012 were included in this study. Blood culture bottles were spiked with clinical isolates, allowed to incubate, and processed by BC-GN. A diagnostic evaluation was performed. In addition, a theoretical evaluation of time to effective and optimal antibiotic was performed, comparing actual antibiotic administration times from chart review (“control”) to theoretical administration times based on BC-GN reporting and antimicrobial stewardship team (AST) review (“intervention”). For organisms detected by the assay, BC-GN correctly identified 95.6% (131/137), with a sensitivity of 97.1% (95% confidence interval [CI], 90.7 to 98.4%) and a specificity of 99.5% (95% CI, 98.8 to 99.8%). CTX-M and OXA resistance determinants were both detected. Allowing 12 h from Gram stain for antibiotic implementation, the intervention group had a significantly shorter duration to both effective (3.3 versus 7.0 h;P< 0.01) and optimal (23.5 versus 41.8 h;P< 0.01) antibiotic therapy. BC-GN with AST intervention can potentially decrease time to both effective and optimal antibiotic therapy in GN BSI.

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