Evaluation of the Liquid Colony™ Produced by the FAST System for Shortening the Time of Bacterial Identification and Phenotypic Antimicrobial Susceptibility Testing and Detection of Resistance Mechanisms from Positive Blood Cultures

Abstract

Background: the aim of this study was to evaluate the performance of the Liquid Colony™ (LC) generated directly from positive blood cultures (PBCs) by the FAST System (Qvella, Richmond Hill, ON, Canada) for rapid identification (ID) and antimicrobial susceptibility testing (AST) compared with the standard of care (SOC) workflow. Methods: Anonymized PBCs were processed in parallel by the FAST System and FAST PBC Prep cartridge (35 min runtime) and SOC. ID was performed by MALDI-ToF mass spectrometry (Bruker, Billerica, MA, USA). AST was performed by reference broth microdilution (Merlin Diagnostika, Bornheim, Germany). Carbapenemase detection was carried out with the lateral flow immunochromatographic assay (LFIA) RESIST-5 O.O.K.N.V. (Coris, Gembloux, Belgium). Polymicrobial PBCs and samples containing yeast were excluded. Results: 241 PBCs were evaluated. ID results showed 100% genus-level concordance and 97.8% species-level concordance between LC and SOC. The AST results for Gram-negative bacteria showed a categorical agreement (CA) of 99.1% (1578/1593), with minor error (mE), major error (ME), and very major error (VME) rates of 0.6% (10/1593), 0.3% (3/1122), and 0.4% (2/471), respectively. The results from Gram-positive bacteria showed a CA of 99.6% (1655/1662), with mE, ME, and VME rates of 0.3% (5/1662), 0.2% (2/1279), and 0.0% (0/378), respectively. Bias evaluation revealed acceptable results for both Gram-negatives and Gram-positives (−12.4% and −6.5%, respectively). The LC yielded the detection of 14/18 carbapenemase producers by LFIA. In terms of turnaround time, the ID, AST, and carbapenemase detection results were generally obtained one day earlier with the FAST System compared with the SOC workflow. Conclusions: The ID, AST, and carbapenemase detection results generated with the FAST System LC were highly concordant with the conventional workflow. The LC allowed species ID and carbapenemase detection within around 1 h after blood culture positivity and AST results within approximately 24 h, which is a significant reduction in the turnaround time of the PBC workflow.

Rapid diagnostic work-up of Streptococcus dysgalactiae endophthalmitis by a novel culture processing system

“…Intended for automated processing of blood culture specimens, the FAST system has yielded promising results in early studies to support clinical use when paired with various downstream identification and AST platforms [13][14][15][16][17]. Prospective studies have found that for positive blood cultures, FAST system processing can be used to rapidly obtain correct organism identifications by MALDI-TOF in 87-96 % of cases, and AST results with ~98 % categorical agreement with standard of care AST [13][14][15][16][17][18]. Not only has the FAST system been shown to be highly accurate, it has also been shown by other studies to significantly reduce workflow time [17,18].…”

“…Prospective studies have found that for positive blood cultures, FAST system processing can be used to rapidly obtain correct organism identifications by MALDI-TOF in 87-96 % of cases, and AST results with ~98 % categorical agreement with standard of care AST [13][14][15][16][17][18]. Not only has the FAST system been shown to be highly accurate, it has also been shown by other studies to significantly reduce workflow time [17,18].…”