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

Abstract

Bloodstream infections (BSI) are an important cause of morbidity and mortality. Increasing rates of antimicrobial-resistant pathogens limit treatment options, prompting an empirical use of broad-range antibiotics. Fast and reliable diagnostic tools are needed to provide adequate therapy in a timely manner and to enable a de-escalation of treatment. The Accelerate Pheno system (Accelerate Diagnostics, USA) is a fully automated test system that performs both identification and antimicrobial susceptibility testing (AST) directly from positive blood cultures within approximately 7 h. In total, 115 episodes of BSI with Gram-negative bacteria were included in our study and compared to conventional culture-based methods. The Accelerate Pheno system correctly identified 88.7% (102 of 115) of all BSI episodes and 97.1% (102 of 105) of isolates that are covered by the system's identification panel. The Accelerate Pheno system generated an AST result for 91.3% (95 of 104) samples in which the Accelerate Pheno system identified a Gram-negative pathogen. The overall category agreement between the Accelerate Pheno system and culture-based AST was 96.4%, the rates for minor discrepancies 1.4%, major discrepancies 2.3%, and very major discrepancies 1.0%. Of note, ceftriaxone, piperacillintazobactam, and carbapenem resistance was correctly detected in blood culture specimens with extended-spectrum beta-lactamase-producing Escherichia coli (n ϭ 7) and multidrug-resistant Pseudomonas aeruginosa (n ϭ 3) strains. The utilization of the Accelerate Pheno system reduced the time to result for identification by 27.49 h (P Ͻ 0.0001) and for AST by 40.39 h (P Ͻ 0.0001) compared to culture-based methods in our laboratory setting. In conclusion, the Accelerate Pheno system provided fast, reliable results while significantly improving turnaround time in blood culture diagnostics of Gramnegative BSI.KEYWORDS antimicrobial susceptibility testing, bloodstream infections, rapid tests B loodstream infections (BSI) are an important cause of morbidity and mortality, associated with prolonged hospital stays, as well as high costs for health care systems (1-3). Increasing rates of antimicrobial-resistant pathogens, in particular Gramnegative bacteria, limit treatment options, often prompting the empirical use of broad-range antibiotics. Therefore, we need fast and reliable diagnostic tools to speed up both identification (ID) and antimicrobial susceptibility testing (AST) from blood cultures in order to provide adequate therapy in a timely manner and to enable effective antibiotic stewardship interventions (4).

Evaluation of the Accelerate Pheno™ system to identify bacteria and determine antimicrobial susceptibility in positive blood cultures

“…The overall essential agreement and the overall category agreement in our study concurs with the multicentre study of Pancholi and colleagues which reported values of 97% (9). The AST for piperacillin-tazobactam and P. aeruginosa has also been optimized in the latest version of the software (5). The delay in the correct antibiotic therapy in patients with sepsis is a risk factor for mortality (10,11).…”

“…The results of this study support the idea that the Accelerate Pheno TM system may improve turn-around time for identification and AST testing for bacterial bloodstream infections. As previously reported (5)(6)(7), in some cases the Accelerate Pheno TM system detected more than one microorganism in mono-microbial infections. In addition, the ID panel failed to show any results for yeasts, which were detected in two cases by subculture.…”

“…The Accelerate Pheno TM system (Accelerate Diagnostics, Inc.) is an automated platform that uses single-cell microbiology analysis technology to rapidly identify pathogens (1.5 hours) and to determine antibiotic susceptibility (7 hours) directly from the positive blood culture bottle (5-7). The system combines gel electrofiltration and fluorescence in situ hybridization for bacterial identification, as well as automated microscopy to analyse bacterial growth rates and for extrapolating MIC values (5,6). This study prospectively compares the Accelerate Pheno TM system with the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS, Bruker) for identification and the BD Phoenix system (Becton Dickinson, New Jersey, U.S) for AST.…”

Identification and Antibiotic‐Susceptibility Profiling of Infectious Bacterial Agents: A Review of Current and Future Trends

“…A study of BSI by gram‐negative bacteria, demonstrated its capacity to correctly identify 88.7% of all episodes from blood cultures, including 10 polymicrobial BSI. However, in seven of the polymicrobial samples, cultivated gram‐positive organisms were not detected . This device was evaluated to successfully discriminate MRSA/MSSA, clindamycin resistance/susceptibility and VSSA/hVISA/VISA respectively using cefoxitin, erythromycin, and vancomycin .…”

Diagnostic Molecular Microbiology

“…They found the overall category agreement of 96.4%, for sensitive, intermediate, and resistant interpretation between AXDX and culture-based antibiotic susceptibility testing, with the rate for minor discrepancies 1.4% (change between sensitive or resistant and intermediate), major discrepancies 2.3% and 33 very major discrepancies 1.0%. 57…”