(43 days)
The BD Phoenix™ Automated Microbiology System is intended for the rapid identification and in vitro 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 agent ampicillin-sulbactam at a concentration range of 0.5/0.25-32/16 µg/mL to gram-negative ID/AST or AST only Phoenix panels. Ampicillin-sulbactam 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 antimicrobial agent.
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 either a gram-negative or gram-positive isolate. For each isolate, an inoculation equivalent to a 0.5 McFarland standard is prepared in Phoenix ID Broth.
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. 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 degrees Celsius. The instrument makes 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, or resistant).
Acceptance Criteria and Study for BD Phoenix™ Automated Microbiology System – Ampicillin-sulbactam
The BD Phoenix™ Automated Microbiology System for Ampicillin-sulbactam (0.5/0.25-32/16 µg/mL) was evaluated for its substantial equivalence to the NCCLS reference broth microdilution method.
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria for antimicrobial susceptibility testing devices, as outlined in FDA guidance documents (specifically "Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices", March 8, 2000, and "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA", February 5, 2003), typically involve demonstrating high levels of Essential Agreement (EA) and Category Agreement (CA). While explicit numerical acceptance criteria for EA and CA are not directly stated in the provided text, the demonstrated performance is presented. Reproducibility often has an implicit or explicit acceptance criterion of >90% or >95%.
| Performance Metric | Acceptance Criteria (Implicit/Typical for AST Devices) | Reported Device Performance |
|---|---|---|
| Essential Agreement (EA) | High percentage (e.g., typically >90% for clinical isolates) | 1052 samples, EA (%) not explicitly stated numerically, but implied as satisfactory. |
| Category Agreement (CA) | High percentage (e.g., typically >90% for clinical isolates) | 1052 samples, CA = 88.3% |
| Site Reproducibility (Intra-site) | >90% | >90% |
| Site Reproducibility (Inter-site) | >95% | >95% |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size for Test Set: 1052 clinical, stock, and challenge isolates (gram-negative organisms) were tested.
- Data Provenance: Data was collected across "multiple geographically diverse clinical sites within the United States" and included "clinical, stock and challenge isolates." This indicates a prospective and multi-site clinical study design.
3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications
- The document does not specify the number of experts used or their qualifications.
- The ground truth for the test set was established by comparing Phoenix System results to the NCCLS reference broth microdilution method. While this method is a well-established standard, the text does not detail a human "expert" adjudication process for interpreting the reference method's results beyond the method itself.
4. Adjudication Method for the Test Set
- The document does not describe an adjudication method involving human experts (e.g., 2+1, 3+1).
- The comparison was directly between the BD Phoenix System's results and those obtained from the NCCLS reference broth microdilution method. Therefore, the "adjudication" is inherent in the standardized performance of the reference method.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
- No MRMC comparative effectiveness study was done. This study evaluates the performance of an automated system against a reference method, not the improvement of human readers with or without AI assistance.
6. Standalone Performance Study
- Yes, a standalone study was done. The entire study described evaluates the performance of the BD Phoenix™ Automated Microbiology System (algorithm only, as a fully automated system) in determining antimicrobial susceptibility, comparing its results directly to the NCCLS reference broth microdilution method. There is no human-in-the-loop component mentioned for the Phoenix system's AST determination process in this context.
7. Type of Ground Truth Used
- Expert Consensus (via standardized method): The ground truth was established using the NCCLS reference broth microdilution method (AST panels prepared according to NCCLS M7). This method is considered the gold standard for antimicrobial susceptibility testing and represents an expert-developed consensus for determining MIC values.
8. Sample Size for the Training Set
- The document does not specify a separate sample size for a training set. The descriptions focus on the evaluation of the existing system and its performance compared to a reference standard, not on the development or training of a new algorithm. For a device like this, which relies on biochemical and growth detection principles, "training" in the AI sense might not be applicable or explicitly separated from the underlying design and calibration data.
9. How the Ground Truth for the Training Set Was Established
- Since a distinct "training set" is not mentioned, the method for establishing its ground truth is not described.
§ 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.”