Identification of Gram-Negative Bacteria and Genetic Resistance Determinants from Positive Blood Culture Broths by Use of the Verigene Gram-Negative Blood Culture Multiplex Microarray-Based Molecular Assay

Abstract

Bloodstream infection is a serious condition associated with significant morbidity and mortality. The outcome of these infections can be positively affected by the early implementation of effective antibiotic therapy based on the identification of the infecting organism and genetic markers associated with antibiotic resistance. In this study, we evaluated the microarray-based Verigene Gram-negative blood culture (BC-GN) assay in the identification of 8 genus or species targets and 6 genetic resistance determinants in positive blood culture broths. A total of 1,847 blood cultures containing Gram-negative organisms were tested using the BC-GN assay. This comprised 729 prospective fresh, 781 prospective or retrospective frozen, and 337 simulated cultures representing 7 types of aerobic culture media. The results were compared to those with standard bacterial culture and biochemical identification with nucleic acid sequence confirmation of the resistance determinants. Among monomicrobial cultures, the positive percent agreement (PPA) of the BC-GN assay with the reference method was as follows; Escherichia coli, 100%; Klebsiella pneumoniae, 92.9%; Klebsiella oxytoca, 95.5%; Enterobacter spp., 99.3%; Pseudomonas aeruginosa, 98.9%; Proteus spp., 100%; Acinetobacter spp., 98.4%; and Citrobacter spp., 100%. All organism identification targets demonstrated >99.5% negative percent agreement (NPA) with the reference method. Of note, 25/26 cultures containing K. pneumoniae that were reported as not detected by the BC-GN assay were subsequently identified as Klebsiella variicola. The PPA for identification of resistance determinants was as follows; bla CTX-M , 98.9%; bla KPC , 100%; bla NDM , 96.2%; bla OXA , 94.3%; bla VIM , 100%; and bla IMP , 100%. All resistance determinant targets demonstrated >99.9% NPA. Among polymicrobial specimens, the BC-GN assay correctly identified at least one organism in 95.4% of the broths and correctly identified all organisms present in 54.5% of the broths. The sample-to-result processing and automated reading of the detection microarray results enables results within 2 h of culture positivity. Bloodstream infection (BSI) is a serious and life-threatening condition that has been associated with 25% to 80% mortality (1, 2). The outcome of BSI can be dependent on host factors, such as underlying comorbidities, and microbiological factors, including the type of infecting organism and its susceptibility to antibiotics. It is estimated that up to 30% of hospital-acquired BSI are attributable to Gram-negative organisms (3). Infections caused by these bacteria, particularly when acquired in the hospital, have been associated with 15% to 29% increased crude mortality rates compared with those of the case controls (4, 5). This is particularly true for infections with multidrug-resistant organisms, including those harboring extended-spectrum ␤-lactamases (ESBLs) or carbapenemases, which have been associated with prolonged hospital stay and increased 30-day mortality (6, 7).Perhaps the most important in...

Evaluation of the Accelerate Pheno System for Fast Identification and Antimicrobial Susceptibility Testing from Positive Blood Cultures in Bloodstream Infections Caused by Gram-Negative Pathogens

“…Only one false-positive Gramnegative organism was detected in an E. coli BSI, in which the Accelerate Pheno system additionally reported Klebsiella species. The sensitivity values are comparable to published performance data for the molecular Verigene Gram-negative blood culture assay (Nanosphere, IL) (14)(15)(16)(17)(18)(19), as well as the BioFire FilmArray blood culture identification panel (BioFire; bioMérieux SA, USA) for the detection of Gram-negative, Gram-positive, and fungal pathogens (11,12,(20)(21)(22)(23)(24).…”

Clinical and laboratory considerations for the rapid detection of carbapenem-resistant Enterobacteriaceae

“…Additionally, among the simulated specimens, the Verigene did not detect 2/52 bla NDM and 1/58 bla OXA (again, a bla OXA-23 ), whereas 68/68 bla VIM and 47/47 bla IMP were detected. 23 The second study that evaluated the Verigene Ò was performed across 3 hospitals in Japan, a country where IMP carbapenemases are prevalent. This study evaluated 141 positive blood cultures (1 that grew an IMP-producing isolate), and 205 blood cultures that were seeded with Gram-negative bacteria.…”

Benefits of Adding a Rapid PCR-Based Blood Culture Identification Panel to an Established Antimicrobial Stewardship Program

“…These include fluorescence in situ hybridization, matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, and nucleic acid hybridization and amplification assays. Comprehensive, panel-based molecular diagnostic assays that detect all of the major bloodstream pathogens and selected antimicrobial resistance genes are now available for direct testing of positive blood cultures (9,10,11). A number of examples in the literature suggest that shortening the time to appropriate therapy due to rapid diagnostic tests may lessen the clinical and economic burden of BSI (12).…”