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ETEST® is a manual, quantitative technique for determination of antimicrobial susceptibility of non-fastidious Gram-negative and Gram-positive aerobic bacteria and fastidious bacteria. The system comprises a predefined antibiotic gradient which is used to determine the Minimum Inhibitory Concentration (MIC, in ug/mL) of different antimicrobial agents against microorganisms tested on agar media after overnight incubation.

Meropenem/Vaborbactam has been shown to be active against the Gram-negative aerobic microorganisms listed below according to the FDA label for this antimicrobial agent.

ETEST® MEV can be used to determine the MIC of Meropenem/Vaborbactam against the following microorganisms:

Active both in vitro and in clinical infections: Enterobacter cloacae complex Escherichia coli Klebsiella pneumoniae

In vitro data are available for the following microorganisms, but clinical significance is unknown:

• Citrobacter freundii Citrobacter koseri Klebsiella aerogenes Klebsiella oxytoca Morganella morganii Providencia spp. Serratia marcescens

ETEST® is a thin, inert and non-porous plastic strip carrying on one side (A) the MIC reading scale in ug/mL, and on the other side (B) a predefined antibiotic gradient.

When the strip is applied to an inoculated agar surface, the preformed antibiotic gradient immediately transfers into the agar matrix, then forming a stable, continuous and exponential gradient of antibiotic concentrations directly underneath the strip. Bacterial growth becomes visible during incubation, and a symmetrical inhibition ellipse centered along the strip appears. The MIC value is read from the scale in terms of ug/mL at complete inhibition of bacterial growth, where the pointed end of the ellipse intersects the strip.

ETEST® Meropenem/Vaborbactam contains a range of meropenem from 0.004 to 64 ug/mL, overlaid with a fixed concentration of 8 µg/mL of vaborbactam.

This document describes the performance study and acceptance criteria for the ETEST® Meropenem/Vaborbactam (MEV) device, an antimicrobial susceptibility test system.

1. Table of Acceptance Criteria and Reported Device Performance

The performance of the ETEST® Meropenem/Vaborbactam device was evaluated against the CLSI M07-A10 January 2015 broth microdilution reference method. The acceptance criteria and the device's reported performance are summarized below:

Notes:

• Essential Agreement (EA): Defined as the percentage of MIC values within ± 1 dilution of the reference method.
• Category Agreement (CA): Not explicitly defined in this document but generally refers to agreement in interpretation (Susceptible, Intermediate, Resistant) between the test method and the reference method.
• The document states that the performance met acceptable levels as defined in the FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems and CLSI M100-S28 January 2018. The specific numerical acceptance thresholds are implied by the statement "acceptable performance" and the satisfactory agreement percentages reported.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size for Test Set: The species and their counts that comprised the Enterobacteriaceae (excluding Proteus mirabilis) test isolates are provided:
  • C. freundii: 32
  • C. koseri: 32
  • K. aerogenes: 33
  • E. cloacae complex: 98
  • E. coli: 136
  • K. oxytoca: 31
  • K. pneumoniae: 128
  • M. morganii: 31
  • P. rettgeri: 21
  • P. stuartii: 21
  • S. marcescens: 31
  • Total number of isolates: 594
• Data Provenance: The document states that "External evaluations were conducted with fresh and stock clinical isolates, as well as a set of challenge strains." This indicates that the data are from real-world clinical samples (retrospective or prospective collections) and likely representative of strains encountered in clinical settings, supplemented with challenge strains designed to test specific resistance mechanisms. The country of origin is not explicitly stated, but the submitter's address is France.

3. Number of Experts Used to Establish Ground Truth for the Test Set and Their Qualifications

• This study evaluates an Antimicrobial Susceptibility Test (AST) system. The "ground truth" for ASTs is typically established by specific, standardized laboratory reference methods (e.g., CLSI broth microdilution), not by human expert interpretation of images or clinical data.
• Therefore, the concept of "number of experts" and their qualifications as applies to image-based AI studies (like those with radiologists) is not directly applicable here. The "experts" in this context would be the skilled laboratory personnel who meticulously performed the CLSI broth microdilution reference method, ensuring adherence to the standard protocol.

4. Adjudication Method for the Test Set

• Not applicable in the context of an AST device performance study where the ground truth is a standardized quantitative laboratory method (CLSI broth microdilution). The comparison is direct between the ETEST® results and the reference method results. There is no "adjudication" in the sense of resolving disagreements between human readers or between human readers and an AI.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was Done

• No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not performed. MRMC studies are primarily relevant for imaging-based diagnostic aids where human readers interpret medical images with or without AI assistance. This submission pertains to a laboratory diagnostic device that determines quantitative antimicrobial susceptibility, not an imaging AI.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) was Done

• Yes, the performance study effectively measures the "standalone" performance of the ETEST® system. The ETEST® device generates a MIC value, and this value is directly compared to the reference method's MIC value without human interpretation influencing the ETEST® result itself. The human component is involved in applying the ETEST® strip and reading the inhibition zone, but this is a direct measurement against a scale rather than a subjective interpretation. The agreement percentages (EA and CA) reflect the accuracy of the device in generating these values compared to the reference.

7. The Type of Ground Truth Used

• Gold Standard Ground Truth: The ground truth for this study was established using the CLSI (Clinical and Laboratory Standards Institute) M07-A10 January 2015 broth microdilution reference method. This is a widely accepted, standardized, and highly reproducible method considered the gold standard for determining Minimum Inhibitory Concentrations (MICs) of antimicrobial agents.

8. The Sample Size for the Training Set

• This device is not an AI model that undergoes a "training phase" in the conventional sense. The "training set" concept (data used to train a machine learning algorithm) does not apply here. ETEST® is a chemical-biological device with a physical mechanism of action (predefined antibiotic gradient diffusion), not a software algorithm that learns from data. Its performance is inherent to its design and manufacturing.
• Therefore, there is no "training set" in the context of machine learning. The studies described are for validation (performance evaluation) against a reference standard.

9. How the Ground Truth for the Training Set Was Established

• As explained above, there is no "training set" for this type of device. The ground truth for the performance evaluation (test set) was established by the CLSI broth microdilution reference method (see point 7).

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