(128 days)
The BD Phoenix™ Automated Microbiology System is intended for the in vitro rapid identification and antimicrobial susceptibility testing of isolates from pure culture of most aerobic and facultative anaerobic gram negative and gram positive bacteria of human origin.
The BD Phoenix™ Automated Microbiology System is intended for in vitro quantitative determination of antimicrobial susceptibility by minimal inhibitory concentration (MIC) of most gram-negative aerobic and facultative anaerobic bacteria isolates from pure culture for Enterobacteriaceae and Non-Enterobacteriaceae and most gram-positive bacteria isolates from pure culture belonging to the genera Staphylococcus and Enterococcus.
This premarket notification is for the addition of the antimicrobial Gatifloxacin at concentrations of 0.25-8 µg to Gram negative and Gram positive ID/AST or AST only Phoenix panels. Gatifloxacin has been shown to be active in vitro against most strains of microorganisms listed below, as described in the FDA-approved package insert for this antimicrobic.
The BD Phoenix Automated Microbiology System (Phoenix System) is an automated system for the rapid identification (ID) and antimicrobial susceptibility testing (AST) of clinically relevant bacterial isolates. The system includes the following components:
- . BD Phoenix instrument and software.
- BD Phoenix panels containing biochemicals for organism ID testing and . antimicrobial agents for AST determinations.
- . BD Phoenix ID Broth used for performing ID tests and preparing AST Broth inoculum.
- . BD Phoenix AST Broth used for performing AST tests only.
- BD Phoenix AST Indicator solution added to the AST broth to aid in bacterial growth . determination.
The Phoenix panel is a sealed and self-inoculating molded polystyrene tray with 136 micro-wells containing dried reagents. Organisms for susceptibility testing must be a pure culture and preliminarily identified as a gram-negative or gram-positive isolate. For each isolate, an inoculum suspension equivalent to a 0.5 McFarland standard is prepared in the Phoenix ID broth. Prior to inoculating the Phoenix AST broth, one drop of Phoenix AST indicator solution is added to the uninoculated AST broth. The AST broth is then inoculated using the organism suspension from the ID broth. The Phoenix antimicrobial susceptibility test is inoculated with the AST broth. Inoculated panels are loaded into the Phoenix instrument.
The Phoenix AST method is a broth based microdilution test. The Phoenix system utilizes a redox indicator for the detection of organism growth in the presence of an antimicrobial agent. Measurements of changes to the indicator as well as bacterial turbidity are used in the determination of bacterial growth. Each AST panel configuration contains several antimicrobial agents with a wide range of two-fold doubling dilution concentrations.
The instrument houses the panels where they are continuously incubated at a nominal temperature of 35°C. The instrument takes readings of the panels every 20 minutes. The readings are interpreted to give an identification of the isolate, minimum inhibitory concentration (MIC) values and category interpretations. S. I. or R (sensitive, intermediate, and resistant).
Here's an analysis of the acceptance criteria and study details for the BD Phoenix™ Automated Microbiology System (for Gatifloxacin) based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria are implied by the FDA guidance document "Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices", March 8, 2000, and the predicate device (NCCLS broth microdilution method). The key performance metrics are Essential Agreement (EA) and Category Agreement (CA). A general acceptance of ">90%" for both EA and CA is mentioned for the Phoenix panels.
| Metric | Acceptance Criteria (Implied) | Reported Device Performance (Gram-Negative) | Reported Device Performance (Gram-Positive) |
|---|---|---|---|
| Essential Agreement (EA) | > 90% | 98.8% | 98.6% |
| Category Agreement (CA) | > 90% | 96.1% | 90.1% |
| Intra-site Reproducibility | > 95% | > 95% (Overall for both) | > 95% (Overall for both) |
| Inter-site Reproducibility | > 95% | > 95% (Overall for both) | > 95% (Overall for both) |
2. Sample Size Used for the Test Set and Data Provenance
- Gram-Negative Isolates:
- Test Set Sample Size (EA): 7160 organism/antimicrobic combinations
- Test Set Sample Size (CA): 2169 organism/antimicrobic combinations
- Gram-Positive Isolates:
- Test Set Sample Size (EA & CA): 1180 organism/antimicrobic combinations
- Data Provenance: The clinical studies were conducted at "ten geographically diverse sites across the United States." The isolates included both "Challenge set isolates" and "clinical isolates." Although not explicitly stated as retrospective or prospective for the clinical isolates, the nature of "clinical studies" for device performance typically implies a prospective or at least concurrently collected and tested set of real-world samples. Challenge set isolates are usually pre-selected and may originate from a collection.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
The document does not specify the number or qualifications of experts used to establish the ground truth. The ground truth was established by:
- For "Challenge set isolates": "expected results for each organism/antimicrobic combination." This implies a pre-determined or expert-confirmed result.
- For "clinical isolates": "results obtained from the reference broth microdilution method." This is a standardized laboratory method, not reliant on individual human expert interpretation for "ground truth" in the same way an image adjudication might be.
4. Adjudication Method for the Test Set
Not applicable. The ground truth for clinical isolates was established by a reference laboratory method (NCCLS broth microdilution method), which is a quantitative and standardized test, not an interpretive one requiring adjudication by human experts. For Challenge set isolates, the "expected results" are likely pre-defined based on known characteristics.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, If So, What Was the Effect Size of How Much Human Readers Improve with AI vs. Without AI Assistance
Not applicable. The BD Phoenix™ Automated Microbiology System is an automated device designed to replace or assist in the traditional manual process of antimicrobial susceptibility testing. It is not an AI-assisted diagnostic tool for human readers, but rather a system that performs the AST itself. Therefore, an MRMC study measuring human reader improvement with or without AI assistance is not relevant to this device.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, a standalone study was done. The entire premise of the BD Phoenix™ System is its automated determination of MIC values and category interpretations (S, I, R). The "Phoenix AST method is a broth based microdilution test" where "The instrument takes readings of the panels every 20 minutes. The readings are interpreted to give an identification of the isolate, minimum inhibitory concentration (MIC) values and category interpretations." This describes the device's standalone performance compared to the reference method.
7. The Type of Ground Truth Used
- For Clinical Isolates: The ground truth was established using the NCCLS broth microdilution method, which serves as the gold standard reference method for antimicrobial susceptibility testing.
- For Challenge Set Isolates: The ground truth was based on "expected results for each organism/antimicrobic combination," which likely means pre-defined, known results for a panel of well-characterized strains.
8. The Sample Size for the Training Set
The document does not explicitly mention a "training set" in the context of machine learning. The system's performance is compared against a reference method. Therefore, the concept of a distinct training set for an algorithm, as typically defined in AI/ML, isn't directly applicable or described in this regulatory submission. The system's design and calibration would have been based on extensive development data, but this is not detailed as a "training set" in the provided text.
9. How the Ground Truth for the Training Set Was Established
As no explicit "training set" in the AI/ML sense is mentioned, the method for establishing its ground truth is not described. The system's underlying principles are based on established microbiology (redox indicators, turbidity measures) for growth detection and the NCCLS M7 standard for microdilution testing, rather than a learned algorithm that requires a labeled training set for its development in the same way a diagnostic AI would.
§ 866.1645 Fully automated short-term incubation cycle antimicrobial susceptibility system.
(a)
Identification. A fully automated short-term incubation cycle antimicrobial susceptibility system is a device that incorporates concentrations of antimicrobial agents into a system for the purpose of determining in vitro susceptibility of bacterial pathogens isolated from clinical specimens. Test results obtained from short-term (less than 16 hours) incubation are used to determine the antimicrobial agent of choice to treat bacterial diseases.(b)
Classification. Class II (special controls). The special control for this device is FDA's guidance document entitled “Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA.”