(57 days)
ETEST® is a manual, quantitative technique for the determination of antimicrobial susceptibility of non-fastidious Gram-negative and Gram-positive aerobic bacteria. The system comprises a predefined antibiotic gradient which is used to determine the Minimum Inhibitory Concentration (MIC, in µg/mL) of different antimicrobial agents against microorganisms tested on agar media after overnight incubation.
Sulbactam/Durlobactam has been shown to be active against the Gram-negative aerobic microorganisms listed below according to the FDA label for this antimicrobial agent.
ETEST® SUD can be used to determine the MIC of Sulbactam/Durlobactam against the following microorganisms:
• Acinetobacter baumannii-calcoaceticus complex
ETEST® is a thin, inert and non-porous plastic strip carrying the MIC reading scale in us/mL on one side and a predefined antibiotic gradient on the other side.
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® Sulbactam/Durlobactam contains a range of Sulbactam from 0.004 to 64 µg/mL, overlaid with a fixed concentration of 4 µg/mL of Durlobactam.
Here's a breakdown of the acceptance criteria and study details for the ETEST® Sulbactam/Durlobactam (SUD) device, based on the provided FDA 510(k) summary:
Acceptance Criteria and Reported Device Performance
| Acceptance Criteria | Reported Device Performance (ETEST® Sulbactam/Durlobactam) |
|---|---|
| Essential Agreement (EA) | 97.7% |
| Category Agreement (CA) | 98.4% |
| Reproducibility (Best-case) | 99.5% |
| Reproducibility (Worst-case) | 99.5% |
| Quality Control | Results within expected range > 95% of the time |
| Meets Guidance Document Performance Requirements | Yes |
Note: The document states that ETEST® Sulbactam/Durlobactam (SUD) demonstrated substantially equivalent performance compared with the CLSI M07-11th Ed (January 2018) broth microdilution reference method, following rules from the FDA Class II Special Controls Guidance Document and specifications in CLSI M100 330 (March 2023).
Study Details
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Sample Size Used for the Test Set and Data Provenance:
- Sample Size (Test Set): 562 strains of Acinetobacter baumannii-calcoaceticus complex.
- Data Provenance: The document states "External evaluations were conducted with fresh and stock clinical isolates, as well as a set of challenge strains." This suggests a combination of retrospective (stock clinical isolates) and potentially prospective (fresh clinical isolates) data. The country of origin is not explicitly mentioned but is likely multi-site given the nature of such evaluations for regulatory clearance.
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Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications:
- The document implies that the CLSI broth microdilution reference method was used as the ground truth. This method is a standardized laboratory procedure and does not typically involve "experts" in the sense of human readers adjudicating images or cases. Instead, it relies on precise technical execution and interpretation according to established CLSI guidelines. Therefore, the concept of a number of experts and their qualifications doesn't directly apply in the same way it would for imaging diagnostics. The "experts" in this context would be the technicians performing the reference method and interpreting the results according to CLSI standards.
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Adjudication Method for the Test Set:
- Not applicable as the ground truth is established by a standardized laboratory reference method (CLSI broth microdilution), not human adjudication. The performance metrics (EA, CA) are calculated by comparing the device's MIC values to those obtained from the reference method.
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If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was Done:
- No, an MRMC comparative effectiveness study was not done. This type of study is primarily relevant for diagnostic devices where human readers interpret results, and the study would assess how AI assistance impacts their performance. For antimicrobial susceptibility testing (AST) devices like ETEST®, the comparison is between the automated/manual device and a standardized reference method.
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If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) was Done:
- Yes, the performance characteristics (Essential Agreement and Category Agreement) are presented for the ETEST® device in standalone mode, comparing its results directly to the CLSI broth microdilution reference method. While ETEST® is a manual technique, its performance evaluation is based on its ability to produce MIC values that align with the reference method. The note about "swabs were used for plate inoculation/streaking and forceps were used for ETEST® strip application" and that "Testing with the optional Inoculator RETRO C80™, Vacuum Pen NEMA C88™, and Applicator SIMPLEX C76™ was not evaluated" confirms that the reported performance reflects the manual ETEST® process itself, without additional automated assistance that might change interpretation.
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The Type of Ground Truth Used:
- Standardized Laboratory Reference Method: The ground truth was established using the CLSI M07-11th Ed (January 2018) broth microdilution reference method. This is considered the gold standard for antimicrobial susceptibility testing.
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The Sample Size for the Training Set:
- The document does not explicitly state the sample size for a "training set." For an AST device like ETEST®, "training" would typically refer to the development and internal validation phases before external clinical evaluations. The information provided focuses on the performance evaluation using the specified test set.
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How the Ground Truth for the Training Set Was Established:
- As no specific "training set" is detailed in this regulatory summary, the method for establishing ground truth for such a set is not provided. However, it can be inferred that any internal development or validation would also rely on comparisons to established reference methods (like CLSI broth microdilution) for consistency.
§ 866.1640 Antimicrobial susceptibility test powder.
(a)
Identification. An antimicrobial susceptibility test powder is a device that consists of an antimicrobial drug powder packaged in vials in specified amounts and intended for use in clinical laboratories for determining in vitro susceptibility of bacterial pathogens to these therapeutic agents. Test results are used to determine the antimicrobial agent of choice in the treatment of bacterial diseases.(b)
Classification. Class II (performance standards).