Rapid AST: Possibility of inferring resistance mechanisms with complex phenotypes / Pruebas rápidas de sensibilidad a los antimicrobianos: ¿es posible inferir mecanismos de resistencia con fenotipos complicados?

The new automated systems designed for rapid performance of AST have significantly reduced the response time for susceptibility testing of microorganisms causing bacteremia and sepsis. The Accelerate Pheno® system (AAC) is one such system. Our objective for this study was to determine whether the AAC system is capable of providing an accurate susceptibility profile to infer resistance mechanisms in different carbapenemase-producing isolates when compared to the MicroScan WalkAway System (MWS). Disk diffusion method was also performed on all isolates as a reference method. Additionally, we compared the results obtained with the routine AST production system. We selected 19 isolates from the cryobank of the Microbiology department, all of which were carbapenemase-producing gram-negative bacilli. AAC was able to identify and infer the resistance of a total of 10 isolates, with an EA and CA of 84.2% for meropenem and 88.2% and 64.7% for ertapenem EA and CA, respectively. If we consider the disk diffusion technique, the CA was 57.9% and 76.5% for meropenem and ertapenem. However, in the presence of carbapenemases, AAC was not able to provide adequate MICs or infer the resistance mechanisms of the isolates accurately. Further studies with a larger number of isolates, including the new antibiotics ceftolozane/tazobactam and ceftazidime/avibactam, are needed for a more comprehensive comparison. (AU)

Los nuevos sistemas automatizados diseñados para la realización rápida de antibiogramas han reducido significativamente el tiempo de respuesta para las pruebas de susceptibilidad de los microorganismos causantes de bacteriemia y sepsis. El sistema Accelerate Pheno® (AAC) es uno de ellos. Nuestro objetivo para este estudio era determinar si el sistema AAC es capaz de proporcionar un perfil de sensibilidad preciso para inferir mecanismos de resistencia en diferentes aislados productores de carbapenemasas en comparación con el sistema MicroScan WalkAway (MWS). El método de disco difusión fue incluido también en todos los aislados como método de referencia. Además, comparamos los resultados obtenidos con el sistema rutinario de producción de antibiogramas rápidos. Seleccionamos 19 aislados del criobanco del departamento de Microbiología, todos ellos bacilos gramnegativos productores de carbapenemasas. AAC fue capaz de identificar e inferir la resistencia de un total de 10 aislados, con una EA y CA del 84,2% para el meropenem y del 88,2% y 64,7% para la EA y CA del ertapenem, respectivamente. Si consideramos la técnica de disco difusión, la CA fue de un 57.9% y de un 76.5% para meropenem y ertapenem. Sin embargo, en presencia de carbapenemasas, AAC no fue capaz de proporcionar CMIs adecuadas ni de inferir con precisión los mecanismos de resistencia de los aislados. Se necesitan más estudios con un mayor número de aislados incluyendo también los nuevos antibióticos ceftolozano/tazobactam y ceftazidima/avibactam para una comparación más exhaustiva. (AU)

Rapid AST: Possibility of inferring resistance mechanisms with complex phenotypes.

The new automated systems designed for rapid performance of AST have significantly reduced the response time for susceptibility testing of microorganisms causing bacteremia and sepsis. The Accelerate Pheno® system (AAC) is one such system. Our objective for this study was to determine whether the AAC system is capable of providing an accurate susceptibility profile to infer resistance mechanisms in different carbapenemase-producing isolates when compared to the MicroScan WalkAway System (MWS). Disk diffusion method was also performed on all isolates as a reference method. Additionally, we compared the results obtained with the routine AST production system. We selected 19 isolates from the cryobank of the Microbiology department, all of which were carbapenemase-producing gram-negative bacilli. AAC was able to identify and infer the resistance of a total of 10 isolates, with an EA and CA of 84.2% for meropenem and 88.2% and 64.7% for ertapenem EA and CA, respectively. If we consider the disk diffusion technique, the CA was 57.9% and 76.5% for meropenem and ertapenem. However, in the presence of carbapenemases, AAC was not able to provide adequate MICs or infer the resistance mechanisms of the isolates accurately. Further studies with a larger number of isolates, including the new antibiotics ceftolozane/tazobactam and ceftazidime/avibactam, are needed for a more comprehensive comparison.

Impact of Accelerate Pheno and BacT/Alert Virtuo on Clinical Processes and Outcomes in Patients with Sepsis and Concurrent Gram-Negative Bacteremia.

The Accelerate Pheno and BacT/Alert Virtuo systems may improve bacteremia management. Here, we evaluated the impact of both devices on outcomes in patients with sepsis and concurrent Gram-negative bacteremia. This quasiexperimental study included a retrospective preimplementation and a prospective postimplementation group. Patients ≥18 years old with Gram-negative bacteremia were included. Patients with neutropenia, pregnant patients, those who were transferred from an outside hospital with active bloodstream infections, and those with polymicrobial bacteremia were excluded. Blood culture incubation in the BacT/Alert 3D device and microdilution antimicrobial susceptibility testing from culture plate growth were used prior to implementation of the BacT/Alert Virtuo and Accelerate Pheno systems. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) identification directly from blood culture was used pre- and postimplementation. Time to Gram stain results, identification, susceptibility reporting, initiation of narrow-spectrum Gram-negative therapy at 72 h, 30-day inpatient mortality, sepsis resolution, and length of hospital stay were evaluated. A total of 116 patients were included (63 preimplementation, 53 postimplementation). Median times to Gram stain and susceptibility results were significantly shorter postimplementation (P < 0.001). The postimplementation group had an improved hazard ratio for narrow-spectrum Gram-negative therapy at 72 h (hazard ratio [HR], 2.685 [95% confidence interval {CI}, 1.348 to 5.349]), a reduced hazard ratio for 30-day inpatient mortality (adjusted HR [aHR], 0.150 [95% CI, 0.026 to 0.846]), and improved sepsis resolution (92.5% versus 77.8% [P = 0.030]). The length of hospital stay was unchanged after implementation. We conclude that implementation of the BacT/Alert Virtuo and Accelerate Pheno systems improved microbiology laboratory processes, antibiotic utilization processes, and clinical outcomes. These data support the use of rapid diagnostics in sepsis with concurrent Gram-negative bacteremia.

Comparison of Accelerate PhenoTest BC Kit and MALDI-TOF MS/VITEK 2 System for the rapid identification and antimicrobial susceptibility testing of gram-negative bacilli causing bloodstream infections.

Background: Our laboratory uses matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI) and the VITEK 2 system (DV2) directly from positive blood cultures (BC) for organism identification (ID) and antimicrobial susceptibility testing (AST). Our objective was to compare direct MALDI-DV2 with a commercial BC ID-AST platform, the Accelerate Pheno system (AXDX), in the ID-AST of clinical and seeded BC positive for gram-negative bacilli (GNB). Methods: BC positive for GNB were collected over a 3-mo period and tested using AXDX and direct MALDI-DV2 and compared with conventional methods. A subset of sterile BC were seeded with multi-drug-resistant GNB. Results: Twenty-nine clinical samples and 35 seeded samples were analyzed. Direct MALDI had a higher ID failure rate (31.0%) than AXDX (3.4%; p < 0.001). Time to ID-AST was 1.5-6.9 h, 5.8-16.5 h, and 21.6-33.0 h for AXDX, direct MALDI-DV2, and conventional methods, respectively (p < 0.001). For clinical samples, AXDX and DV2 had essential agreement (EA) or categorical agreement (CA) of more than 96%. For seeded samples, AXDX had EA, CA, VME, ME, and minor error (mE) of 93.2%, 89.0%, 2.2%, 0%, and 9.2%, respectively. AXDX had a large number of non-reports (6.1%) stemming from meropenem testing. DV2 had EA, CA, VME, ME, and mE of 97.5%, 94.7%, 1.3%, 0%, and 4.1%, respectively. Conclusions: Direct MALDI-DV2 and AXDX both had high agreement for clinical samples, but direct MALDI-DV2 had higher agreement when challenged with MDR GNB.

Historique: Le laboratoire des chercheurs fait appel à la spectrométrie de masse à temps de vol par désorption/ionisation laser assistée par matrice (MALDI) et au système VITEK 2 (DV2) directement à partir des hémocultures positives pour identifier les organismes et procéder aux antibiogrammes. Les chercheurs avaient l'objectif de comparer les MALDI­DV2 directs avec le système Accelerate Pheno (AXDX), une plateforme commerciale d'hémoculture, d'identification et d'antibiogramme, pour identifier les organismes et procéder aux antibiogrammes dans les hémocultures cliniques et les hémocultures ensemencées positives aux bacilles à Gram négatif (BGN). Méthodologie: Les chercheurs ont colligé les hémocultures positives aux BGN sur une période de trois mois, ont procédé au dépistage à l'aide du système AXDX et des MALDI­DV2 directs et ont comparé les résultats aux méthodes classiques. Ils ont ensemencé un sous-groupe d'hémocultures stériles avec des BGN multirésistantes. Résultats: Les chercheurs ont analysé 29 échantillons cliniques et 35 échantillons ensemencés. La MALDI directe présentait un taux d'échec d'identification plus élevé (31,0 %) que le système AXDX (3,4 %; p < 0,001). Il fallait de 1,5 à 6,9 heures, de 5,8 à 16,5 heures et de 21,6 à 33,0 heures pour identifier les organismes et procéder aux antibiogrammes à l'aide du système AXDX, des MALDI­DV2 directs et des méthodes classiques, respectivement (p < 0,001). Pour les échantillons cliniques, les systèmes AXDX et DV2 présentaient une concordance essentielle (CE) ou catégorique (CA) de plus de 96 %. Pour les échantillons ensemencés, le système AXDX présentait une CE, une CA, des erreurs très majeures (ETM), des erreurs majeures (EM) et des erreurs mineures (Em) de 93,2 %, 89,0 %, 2,2 %, 0 % et 9,2 %, respectivement. Le système AXDX était lié à un grand nombre d'absences de rapports (6,1 %) découlant des tests de méropénem. Le système DV2 présentait une CE, une CA, des ETM, des EM et des Em de 97,5 %, 94,7 %, 1,3 %, 0 % et 4,1 %, respectivement. Conclusions: Les MALDI­DV2 directs et le système AXDX présentaient une concordance élevée pour les échantillons cliniques, mais les MALDI­DV2 directs étaient associés à une concordance plus élevée en cas de provocation par des BGN multirésistantes.

Clinical Impact of Rapid Species Identification From Positive Blood Cultures With Same-day Phenotypic Antimicrobial Susceptibility Testing on the Management and Outcome of Bloodstream Infections.

BACKGROUND: Timely availability of microbiological results from positive blood cultures is essential to enable early pathogen-directed therapy. The Accelerate Pheno system (ADX) is a novel technology using fluorescence in situ hybridization for rapid species identification (ID) and morphokinetic bacterial analysis for phenotypic antimicrobial susceptibility testing (AST), with promising results. Yet the impact of this technology on clinical management and patient outcome remains unclear. METHODS: We conducted a quasiexperimental before-and-after observational study and analyzed 3 groups with different diagnostic and therapeutic pathways following recent integration of ADX: conventional microbiological diagnostics with and without antimicrobial stewardship program (ASP) intervention, and rapid diagnostics (ADX in addition to conventional standard) with ASP intervention. Primary endpoints were time to adequate, to optimal and to step-down antimicrobial therapy. Secondary endpoints were antimicrobial consumption, in-hospital mortality, length of stay (LOS), and the incidence of Clostridioidesdifficile infection (CDI). RESULTS: Two hundred four patients (conventional diagnostics, n = 64; conventional diagnostics + ASP, n = 68; rapid diagnostics + ASP; n = 72) were evaluated. The use of ADX significantly decreased time from Gram stain to ID (median, 23 vs 2.2 hours, P < .001) and AST (median, 23 vs 7.4 hours, P < .001), from Gram stain to optimal therapy (median, 11 vs 7 hours, P = .024) and to step-down antimicrobial therapy (median, 27.8 vs 12 hours, P = .019). However, groups did not differ in antimicrobial consumption, duration of antimicrobial therapy, mortality, LOS, or incidence of CDI. CONCLUSIONS: Use of ADX significantly reduced time to ID and AST as well as time to optimal antimicrobial therapy but did not affect antimicrobial consumption and clinical outcome.