(34 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 aerobic and facultative anaerobic bacteria isolates from pure culture for Gram-negative aerobic and Non-Enteriaceae and most Gram-positive bacteria isolates from pure Enterococcionains to the genera Staphylococcus and Enterococcus.
This premarket notification is for the addition of the antimicrobial agent cefoxitin at concentrations of 1-32 µg/mL to Gram Positive ID/AST or AST only Phoenix panels. It will also be used as a test to detect methicillin/oxacillin resistance in Staphylococcus aureus in these panels. Cefoxitin has been shown to product in vitro against most strains of microorganisms listed below, as described in the FDA-approved package insert for this antimicrobial agent.
Active In Vitro and in Clinical Infections Against:
Staphylococcus aureus® (including penicillinase-producing strains)
Staphylococcus epidermidisª
a Staphylococci resistant to methicillin/oxacillin should be considered resistant to cefoxitin.
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 containing dried reagents: 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 regarding the acceptance criteria and study for the BD Phoenix™ Automated Microbiology System - Cefoxitin 1-32 µg/mL.
1. Table of Acceptance Criteria and Reported Device Performance:
The document explicitly states acceptance criteria are based on Essential Agreement (EA) and Category Agreement (CA) when compared to the CLSI reference broth microdilution method. While the exact numerical acceptance thresholds for EA and CA are not present in the provided text, the overall conclusion states "The data collected from the substantial equivalence studies demonstrate that testing on the BD Phoenix™ Automated Microbiology System with this antimicrobial agent is substantially equivalent as outlined in the FDA draft guidance document, 'Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices', March 8, 2000." This implies the performance met the criteria set forth in that guidance document.
| Acceptance Criterion | Reported Device Performance |
|---|---|
| Essential Agreement (EA) | Not explicitly stated in numerical percentage, but concluded to be "substantially equivalent" when compared to the CLSI reference broth microdilution method, implying it met the FDA guidance. EA is defined as agreement exactly or within +/- one two-fold dilution to the reference result. |
| Category Agreement (CA) | Not explicitly stated in numerical percentage, but concluded to be "substantially equivalent" when compared to the CLSI reference broth microdilution method, implying it met the FDA guidance. CA is defined as agreement with the reference method with respect to FDA categorical interpretive criteria (susceptible, intermediate, and resistant). |
| Intra-site Reproducibility | Greater than 90% |
| Inter-site Reproducibility | Greater than 95% |
Note: The provided "Table 1: Performance of BD Phoenix System for Gram-Positive Organisms by Drug" is missing critical data points, making it impossible to extract specific numerical EA and CA percentages for Cefoxitin from this table as presented in the document. The table's content is largely unreadable due to formatting issues in the input.
2. Sample Size Used for the Test Set and Data Provenance:
- Test Set Sample Size:
- Clinical Isolates: Not explicitly stated, but clinical isolates were a component of the testing.
- Stock and Challenge Isolates: Not explicitly stated, but these were also tested.
- Reproducibility Study: "a panel of Gram-positive isolates" tested in triplicate on three different days. The exact number of isolates is not specified.
- Data Provenance: Clinical, stock, and challenge isolates were tested across "multiple geographically diverse sites across the United States." This indicates a prospective study (for the clinical isolates, at least) with data originating from the United States.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts:
This information is not provided in the document. The ground truth (reference method) was established by the CLSI reference broth microdilution method, which is a standardized laboratory procedure, not typically relying on "experts" in the sense of human readers.
4. Adjudication Method for the Test Set:
This information is not applicable as the ground truth was established by a standardized laboratory method (CLSI reference broth microdilution) rather than expert review that would require adjudication.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, and the Effect Size of How Much Human Readers Improve with AI vs. Without AI Assistance:
No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This device is an automated microbiology system, not an AI assisting human readers. Its performance is evaluated independently against a reference method.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done:
Yes, the study represents a standalone evaluation of the BD Phoenix™ Automated Microbiology System. The device performs the rapid identification and antimicrobial susceptibility testing automatically, and its results are compared directly to the CLSI reference method. There is no human reader "in-the-loop" for interpreting the device's output and then comparing that to human interpretation of another modality.
7. The Type of Ground Truth Used:
The primary ground truth used was the CLSI reference broth microdilution method, which is a standardized laboratory procedure for determining minimum inhibitory concentrations (MICs) of antimicrobial agents. For Challenge set isolates, the Phoenix System results were compared to "expected results," which would also be pre-defined reference values.
8. The Sample Size for the Training Set:
This information is not applicable/not provided. The BD Phoenix system is an automated instrument with predefined algorithms and reagent-based testing, not a machine learning or AI model that undergoes a "training phase" in the conventional sense. The "training set" concept is typically relevant for AI/ML algorithms where data is used to optimize the model parameters. The development of such systems usually involves extensive R&D and validation but not in the format of a distinct "training set" as described for AI.
9. How the Ground Truth for the Training Set Was Established:
This information is not applicable/not provided for the reasons stated above (not an AI/ML system with a conventional training set). The development of the system would have involved internal validation and calibration using various bacterial strains and reference methods.
§ 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.”