Evaluation of the Speed, Accuracy and Precision of the QuickMIC Rapid Antibiotic Susceptibility Testing Assay With Gram-Negative Bacteria in a Clinical Setting

Microfluidic chip systems for color-based antimicrobial susceptibility test a review

Clinical bacteria pose a significant public health threat, underscoring the need for reliable and rapid diagnostic methods for early disease detection, which can facilitate patient recovery. Current diagnostic methods for rapid pathogen detection often take hours to days and require numerous reagents and lengthy protocols. Microfluidic chip system offers a promising solution for clinical microbiology detection by reducing detection time with minimal setup and providing a point-of-care solution for patients. These systems are also easier to handle and, with advancements in technology, offer more conclusive observations. This review focuses on recent developments in microfluidic chip-based systems that use colored fluorescent and non-fluorescent dyes for phenotypic tests in clinical pathogen detection. Recent advancements in non-conventional observation methods, such as smartphones and software combined with microscopy, are paving the way for microfluidic systems to revolutionize point-of-care devices. Significant challenges for these systems include antimicrobial susceptibility testing protocols, which depend on color formation, observation methods, and reducing detection time. In the future, working with live cultures remains a major hurdle in developing efficient and accurate microfluidic diagnostic systems for antimicrobial susceptibility testing.

A multicenter evaluation of a novel microfluidic rapid AST assay for Gram-negative bloodstream infections

Common phenotypic methods for antimicrobial susceptibility testing (AST) of bacteria are slow, labor intensive, and display considerable technical variability. The QuickMIC system provides rapid AST using a microfluidic linear gradient. Here, we evaluate the performance of QuickMIC at four different laboratories with regard to speed, precision, accuracy, and reproducibility in comparison to broth microdilution (BMD). Spiked (n = 411) and clinical blood cultures (n = 148) were tested with the QuickMIC Gram-negative panel and compared with BMD for the 12 on-panel antibiotics, and 10 defined strains were run at each site to measure reproducibility. Logistic and linear regression analysis was applied to explore factors affecting assay performance. The overall essential agreement and categorical agreement between QuickMIC and BMD were 95.6% and 96.0%, respectively. Very major error, major error, and minor error rates were 1.0%, 0.6%, and 2.4%, respectively. Inter-laboratory reproducibility between the sites was high at 98.9% using the acceptable standard of ±1 twofold dilution. The mean in-instrument analysis time overall was 3 h 13 min (SD: 29 min). Regression analysis indicated that QuickMIC is robust with regard to initial inoculum and delay time after blood culture positivity. We conclude that QuickMIC can be used to rapidly measure MIC directly from blood cultures in clinical settings with high reproducibility, precision, and accuracy. The microfluidics-generated linear gradient ensures high reproducibility between laboratories, thus allowing a high level of trust in MIC values from single testing, at the cost of reduced measurement range compared to BMD.

IMPORTANCE

Increasing antimicrobial resistance underscores the need for new diagnostic solutions to guide therapy, but traditional antimicrobial susceptibility testing (AST) is often inadequate in time-critical diseases such as sepsis. This work presents a novel and rapid AST system with a rapid turnaround of results, which may help reduce the time to guided therapy, possibly allowing early de-escalation of broad-spectrum empirical therapy as well as rapid adjustments to treatments when coverage is lacking.

Evaluation of the quickmic system in the rapid diagnosis of Gram-negative bacilli bacteremia

Rapid microbiological diagnosis of the antibiotic susceptibility of Gram-negative bacilli is a priority in clinical microbiology, especially in cases of bacteremia. The rapid advancement of antimicrobial resistance proposes a challenge for empirical antibiotic therapy and shows the need for fast antibiotic susceptibility diagnostics to guide treatments. The QuickMIC System (Gradientech AB, Uppsala, Sweden) is a recently developed rapid diagnostic tool for antibiotic susceptibility testing. Our study evaluates a rapid phenotypic system (QuickMIC) that provides information on the susceptibility of 12 antibiotics against Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, Acinetobacter baumannii, Enterobacter cloacae, Proteus spp., Citrobacter spp., and Serratia marcescens. A total of 816 antibiotic/microorganism combinations were tested, resulting in eight discrepancies. The concordance between the antibiotics offered by QuickMIC and reference methods (MicroScan WalkAway plus system, Beckman Coulter; Etest (BioMerieux microdilution system (Bruker); Real-time PCR (GeneXpert, Cepheid); and immunochromatography (Biotech) was 99.02%. Time elapsed to obtain a valid minimal inhibitory concentration (MIC) was between 2 and 4 h. The QuickMIC system allows for the early adjustment of antibiotic treatment in these infections. Given the existing limitations of currently available rapid methods, its clinical utility is particularly relevant in the management of P. aeruginosa infections and AmpC-producing Enterobacterales. The use of rapid methods can help diversify antibiotic use and reduce carbapenem consumption.

IMPORTANCE

The rapid diagnosis of antibiotic sensitivity in Gram-negative bacilli is of paramount importance in clinical microbiology, particularly in cases of bacteremia. The escalating challenge of antimicrobial resistance underscores the need for expeditious antibiotic susceptibility diagnostics to guide empirical antibiotic therapy effectively. In light of this, we present our study that evaluates the QuickMIC System, a recently developed rapid diagnostic antibiogram. QuickMIC System, offers a novel approach to phenotypic testing, providing information on the activity of 12 antibiotics against key pathogens, including Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, Acinetobacter baumannii, Enterobacter cloacae, Proteus spp., Citrobacter spp., and Serratia marcescens. Our investigation involved testing a total of 816 antibiotic/microorganism combinations. The study demonstrated an impressive 99.02% concordance between the QuickMIC System and the reference methods, with only eight discrepancies observed. The time to actionable minimum inhibitory concentration (MIC) ranged between 2 and 4 h, highlighting the system's efficiency in providing rapid results.

Rapid Phenotypic and Genotypic Antimicrobial Susceptibility Testing Approaches for Use in the Clinical Laboratory

The rapid rise in increasingly resistant bacteria has become a major threat to public health. Antimicrobial susceptibility testing (AST) is crucial in guiding appropriate therapeutic decisions and infection prevention practices for patient care. However, conventional culture-based AST methods are time-consuming and labor-intensive. Therefore, rapid AST approaches exist to address the delayed gap in time to actionable results. There are two main types of rapid AST technologies- phenotypic and genotypic approaches. In this review, we provide a summary of all commercially available rapid AST platforms for use in clinical microbiology laboratories. We describe the technologies utilized, performance characteristics, acceptable specimen types, types of resistance detected, turnaround times, limitations, and clinical outcomes driven by these rapid tests. We also discuss crucial factors to consider for the implementation of rapid AST technologies in a clinical laboratory and what the future of rapid AST holds.

Blood culture-free ultra-rapid antimicrobial susceptibility testing

Treatment assessment and patient outcome for sepsis depend predominantly on the timely administration of appropriate antibiotics1-3. However, the clinical protocols used to stratify and select patient-specific optimal therapy are extremely slow4. In particular, the major hurdle in performing rapid antimicrobial susceptibility testing (AST) remains in the lengthy blood culture procedure, which has long been considered unavoidable due to the limited number of pathogens present in the patient's blood. Here we describe an ultra-rapid AST method that bypasses the need for traditional blood culture, thereby demonstrating potential to reduce the turnaround time of reporting drug susceptibility profiles by more than 40-60 h compared with hospital AST workflows. Introducing a synthetic beta-2-glycoprotein I peptide, a broad range of microbial pathogens are selectively recovered from whole blood, subjected to species identification or instantly proliferated and phenotypically evaluated for various drug conditions using a low-inoculum AST chip. The platform was clinically evaluated by the enrolment of 190 hospitalized patients suspected of having infection, achieving 100% match in species identification. Among the eight positive cases, six clinical isolates were retrospectively tested for AST showing an overall categorical agreement of 94.90% with an average theoretical turnaround time of 13 ± 2.53 h starting from initial blood processing.

Sedimentation field-flow fractionation for rapid phenotypic antimicrobial susceptibility testing: a pilot study

BACKGROUND

The increase in antibiotic resistance is a major public health issue. The development of rapid antimicrobial susceptibility testing (AST) methods is becoming a priority to ensure early and appropriate antibiotic therapy.

OBJECTIVES

To evaluate sedimentation field-flow fractionation (SdFFF) as a method for performing AST in less than 3 h.

METHODS

SdFFF is based on the detection of early biophysical changes in bacteria, using a chromatographic-type technology. One hundred clinical Escherichia coli strains were studied. A calibrated bacterial suspension was incubated for 2 h at 37°C in the absence (untreated) or presence (treated) of five antibiotics used at EUCAST breakpoint concentrations. Bacterial suspensions were then injected into the SdFFF machine. For each E. coli isolate, retention times and elution profiles of antibiotic-treated bacteria were compared with retention times and elution profiles of untreated bacteria. Algorithms comparing retention times and elution profiles were used to determine if the strain was susceptible or resistant. Performance evaluation was done according to CLSI and the ISO standard 20776-2:2021 with broth microdilution used as the reference method.

RESULTS

AST results from SdFFF were obtained in less than 3 h. SdFFF showed high categorical agreement (99.8%), sensitivity (99.5%) and specificity (100.0%) with broth microdilution. Results for each antimicrobial were also in agreement with the ISO 20776-2 recommendations, with sensitivity and specificity of ≥95.0%.

CONCLUSIONS

This study showed that SdFFF can be used as a rapid, accurate and reliable phenotypic AST method with a turnaround time of less than 3 h.

A multisite validation of a two hours antibiotic susceptibility flow cytometry assay directly from positive blood cultures

BACKGROUND

Rapid antimicrobial susceptibility testing (AST) is urgently needed to provide safer treatment to counteract antimicrobial resistance. This is critical in septic patients, because resistance increases empiric therapy uncertainty and the risk of a poor outcome. We validate a novel 2h flow cytometry AST assay directly from positive blood cultures (PBC) by using a room temperature stable FASTgramneg and FASTgrampos kits (FASTinov® Porto, Portugal) in three sites: FASTinov (site-1), Hospital Ramon y Cajal, Madrid, Spain (site-2) and Centro Hospitalar S. João, Porto, Portugal (site-3). A total of 670 PBC were included: 333 spiked (site-1) and 337 clinical PBC (151 site-2 and 186 site-3): 367 gram-negative and 303 gram-positive. Manufacturer instructions were followed for sample preparation, panel inoculation, incubation (1h/37ºC) and flow cytometry analysis using CytoFlex (Site-1 and -2) or DxFlex (site-3) both instruments from Beckman-Coulter, USA.

RESULTS

A proprietary software (bioFAST) was used to immediately generate a susceptibility report in less than 2 h. In parallel, samples were processed according to reference AST methods (disk diffusion and/or microdilution) and interpreted with EUCAST and CLSI criteria. Additionally, ten samples were spiked in all sites for inter-laboratory reproducibility. Sensitivity and specificity were >95% for all antimicrobials. Reproducibility was 96.8%/95.0% for FASTgramneg and 95.1%/95.1% for FASTgrampos regarding EUCAST/CLSI criteria, respectively.

CONCLUSION

FASTinov® kits consistently provide ultra-rapid AST in 2h with high accuracy and reproducibility on both Gram-negative and Gram-positive bacteria. This technology creates a new paradigm in bacterial infection management and holds the potential to significantly impact septic patient outcomes and antimicrobial stewardship.

Fully Automated EUCAST Rapid Antimicrobial Susceptibility Testing (RAST) from Positive Blood Cultures: Diagnostic Accuracy and Implementation

The objective of this study was to evaluate the accuracy and robustness of a fully automated EUCAST RAST (rapid antimicrobial susceptibility test) directly from positive blood culture and to appreciate its implementation constraints. This study was conducted in two phases: (i) spiked blood culture bottles (BCs) using 779 non-duplicate clinical isolates and (ii) a prospective clinical trial including 534 positive BCs sequentially processed in routine at the Bacteriology Laboratory of Geneva University Hospitals. The RAST results were assessed against EUCAST standardized disk diffusion testing results. Our first finding was that the results of the spiked BCs precisely predicted the clinical trial results. The overall categorical agreements for all species analyzed were greater than 95% at the different time points. RAST for Pseudomonas aeruginosa, however, raised several challenges. The categorical agreement for imipenem was lower than 95% at 6 h and was not improved with longer incubation times. Additionally, piperacillin-tazobactam, ceftazidime, and cefepime cannot be released at 6 h due to suboptimal performances, but the categorical agreement substantially improved at 8 h. Our results establish that the performance of fully automated EUCAST RAST directly from positive blood culture bottles is consistently robust, even for the detection of extended-spectrum β-lactamase (ESBL), carbapenemase-producing bacteria, and methicillin-resistant Staphylococcus aureus (MRSA). The automation markedly enhanced the percentage of readable inhibition zones and reduced the percentage of isolates categorized in the area of technical uncertainty (ATU). In summary, a fully automated EUCAST RAST can substantially improve laboratory workflow by reducing hands-on time and removing the strong constraints linked to manual read-outs at precisely defined times.