(30 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 grampositive 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 Gentamicin at concentrations of 0.25 - 16 ug/mL to Gram Positive ID/AST or AST only Phoenix panels. Gentamicin 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.
Active In Vitro Against:
Aerobic Gram-positive microorganisms Staphylococcus aureus Coagulase-negative staphylococci
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 ● or 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 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. 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, or resistant).
Here's an analysis of the provided text, focusing on the acceptance criteria and the study that proves the device meets them:
Acceptance Criteria and Device Performance for BD Phoenix™ Automated Microbiology System Gentamicin-GP
1. Table of Acceptance Criteria and Reported Device Performance
The core performance metrics for this device are Essential Agreement (EA) and Category Agreement (CA). The study aimed to demonstrate "substantially equivalent performance" to the NCCLS reference broth microdilution method.
| Metric | Acceptance Criteria (Implied by FDA Guidance) | Reported Device Performance |
|---|---|---|
| Essential Agreement (EA) | Not explicitly stated but generally expected to be high (e.g., >90%) for substantial equivalence in AST devices. | 91.9% (n=1223) |
| Category Agreement (CA) | Not explicitly stated but generally expected to be high (e.g., >90-95%) for substantial equivalence in AST devices. | 95.2% (n=1223) |
| Intra-site Reproducibility | >90% | >90% |
| Inter-site Reproducibility | >95% | >95% |
Note on Acceptance Criteria: The document refers to the "FDA Draft guidance document, 'Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices', March 8, 2000." While specific numerical acceptance criteria (e.g., 90% for EA, 95% for CA) are not explicitly printed within this 510(k) summary, these are standard expectations for demonstrating substantial equivalence for AST devices based on FDA guidance at that time. The document's statement of "substantially equivalent performance" after reporting these percentages implies these were the thresholds met.
2. Sample Sizes and Data Provenance
- Test Set Sample Size: 1223 isolates (reported as 'n' for both EA and CA). This includes clinical, stock, and challenge isolates.
- Data Provenance: The isolates were tested "across multiple geographically diverse sites across the United States." The data is prospective for clinical isolates compared to a reference method, and a challenge/stock set was likely retrospective in selection but prospectively tested against the new device.
3. Number of Experts and Qualifications for Ground Truth
The document does not explicitly state the "number of experts" or their "qualifications" in the context of establishing ground truth for the test set.
However, the ground truth was established by:
- The NCCLS reference broth microdilution method for clinical isolates. This is a standardized, well-defined laboratory method, implying trained microbiologists/technicians performed these tests.
- "Expected results" for challenge set isolates. These "expected results" would have been pre-determined by experts following established protocols, but the specific number or qualifications are not provided here.
4. Adjudication Method for the Test Set
No explicit adjudication method (e.g., 2+1, 3+1) is described for the test set. The comparison for clinical isolates was directly against the NCCLS reference method. For challenge isolates, it was against "expected results."
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No MRMC comparative effectiveness study was mentioned. This device is an automated system for antimicrobial susceptibility testing, not an imaging or diagnostic AI tool that assists human readers. Therefore, the concept of "human readers improve with AI vs without AI assistance" does not directly apply here.
6. Standalone (Algorithm Only) Performance Study
Yes, a standalone study was performed. The BD Phoenix™ Automated Microbiology System is an automated device, and its performance was assessed independently by comparing its results against the NCCLS reference method and expected results for challenge isolates. The reported EA and CA percentages represent this standalone capability.
7. Type of Ground Truth Used
- Clinical Isolates: The ground truth was established by the NCCLS reference broth microdilution method. This is a well-accepted laboratory standard for antimicrobial susceptibility testing.
- Challenge Isolates: The ground truth was established by "expected results," which are typically pre-determined and validated results for specific strains.
8. Sample Size for the Training Set
The document does not provide a sample size for a training set. This is a 510(k) premarket notification for an automated microbiology system more akin to a laboratory instrument, not a machine learning algorithm that undergoes explicit 'training' in the conventional sense detailed for modern AI devices. The system's rules and algorithms would have been developed and validated internally, likely using various bacterial strains and antimicrobial concentrations during its engineering phase, but this process is not detailed here as "training data" in the AI sense.
9. How Ground Truth for the Training Set Was Established
As mentioned above, the concept of a separate "training set" with ground truth in the AI context isn't explicitly addressed. The system's internal mechanisms for determining MIC values and categorical interpretations would have been developed based on established microbiological principles, extensive internal testing, and alignment with breakpoints defined by regulatory bodies (like FDA) and standards organizations (like NCCLS). These foundational data and principles would have informed the system's development, but a distinct "training set" for an AI model 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.”