(89 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 cefpodoxime at concentrations of 0.125-8 ug/mL to Gram-negative ID/AST or AST only Phoenix panels. Cefpodoxime 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 and in Clinical Infections Against: Escherichia coli Klebsiella pneumoniae
Active In Vitro Against: Citrobacter koseri (formerly Citrobacter diversus) Klebsiella oxytoca Proteus vulgaris
The BD Phoenix Automated Microbiology System (Phoenix System) is an automated system for the rapid identification (ID) and antimicrobial susceptibility testing (AST) of clinically releyant 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 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 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. Phoenix panels are inoculated with a specified organism density and placed in the instrument.
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).
Acceptance Criteria and Device Performance Study for BD Phoenix™ Automated Microbiology System – Cefpodoxime
The BD Phoenix™ Automated Microbiology System, with the addition of Cefpodoxime (0.125-8 µg/mL), was evaluated for its ability to determine antimicrobial susceptibility in Gram-negative organisms. The study demonstrated substantial equivalence to the CLSI reference broth microdilution method.
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria for antimicrobial susceptibility testing systems, as outlined by the FDA guidance document "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA", February 5, 2003, and "Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices", March 8, 2000, are generally based on Essential Agreement (EA) and Category Agreement (CA) thresholds. While the exact numerical criteria are not explicitly stated as "acceptance criteria" in the provided text, the study evaluates performance against these metrics.
| Performance Metric | Acceptance Criteria (Implicit from FDA Guidance) | Reported Device Performance (Cefpodoxime - Gram-negative Organisms) | Comments |
|---|---|---|---|
| Essential Agreement (EA) | Typically ≥ 90% | Not explicitly stated but implied to meet substantial equivalence | EA occurs when the BD Phoenix™ Automated Microbiology System agrees exactly or within + one two-fold dilution to the reference result. The study concludes substantial equivalence based on overall performance. |
| Category Agreement (CA) | Typically ≥ 90% | Not explicitly stated but implied to meet substantial equivalence | CA occurs when the BD Phoenix™ Automated Microbiology System agrees with the reference method with respect to the FDA categorical interpretive criteria (susceptible, intermediate, and resistant). The study concludes substantial equivalence based on overall performance. |
| Intra-site Reproducibility | Generally > 90% | > 90% | Achieved through triplicate testing on three different days at each site. |
| Inter-site Reproducibility | Generally > 95% | > 95% | Evaluated across three sites. |
Note: The provided table in the summary (Table 1: Performance of BD Phoenix System for Gram-negative Organisms by Drug) appears corrupted and does not clearly present the numerical EA and CA values for Cefpodoxime. However, the text explicitly states: "The performance of the Phoenix System was assessed by calculating Essential Agreement (EA) and Category Agreement (CA) to expected/reference results for all isolates tested," and then concludes that the system "demonstrates that testing on the BD Phoenix™ Automated Microbiology System with this antimicrobial agent is substantially equivalent." This implies that the observed EA and CA values met the FDA's criteria for substantial equivalence.
2. Sample Size Used for the Test Set and Data Provenance
- Test Set Sample Size: The exact number of isolates used in the clinical study (test set) is not specified. It is mentioned as "Clinical, stock and challenge isolates were tested."
- Data Provenance: The isolates were collected from "multiple geographically diverse sites across the United States." This indicates prospective and retrospective data collection, as "stock and challenge isolates" often represent curated collections, while "clinical isolates" are likely collected prospectively during the study period.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications
This information is not provided in the given text. For antimicrobial susceptibility testing, the "ground truth" is typically established by performing the CLSI reference broth microdilution method. While this method requires skilled laboratory personnel, it doesn't typically involve "experts" in the same way, for example, a radiologist reviewing images. The reference method itself is the gold standard.
4. Adjudication Method for the Test Set
The concept of an "adjudication method" (like 2+1 or 3+1) is not applicable here. This kind of adjudication is usually for subjective interpretations (e.g., medical image diagnosis) where human disagreement needs to be resolved. In AST, the reference method provides a quantitative result (MIC) and a categorical interpretation (S, I, R) based on established breakpoints, which is considered objective. Discordant results between the device and the reference method are typically analyzed, but not "adjudicated" by experts in the traditional sense.
5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study Was Done
No, an MRMC comparative effectiveness study was not explicitly described. The study compares the automated system's performance to a reference method, not to human readers with vs. without AI assistance. The BD Phoenix System is an automated system for determining antimicrobial susceptibility, acting as a standalone diagnostic tool rather than an assistance tool for human interpretation in the context of the provided document.
6. If a Standalone Study Was Done
Yes, a standalone study was done. The entire study described is a standalone performance evaluation of the BD Phoenix™ Automated Microbiology System with Cefpodoxime. The system, without human intervention in the interpretation phase, generates MIC values and categorical interpretations that are then compared to the CLSI reference method.
7. The Type of Ground Truth Used
The type of ground truth used was the CLSI reference broth microdilution method. This is the widely accepted gold standard for antimicrobial susceptibility testing. For challenge set isolates, the ground truth was "expected results," which are typically pre-determined based on extensive prior testing or known characteristics of the strains.
8. The Sample Size for the Training Set
The document does not specify the sample size for the training set. The descriptions focus on the evaluation of the device's performance against reference methods. As an in vitro diagnostic device for susceptibility testing, the "training set" might refer to the data used historically to develop and validate the algorithms within the Phoenix system itself—information not typically disclosed in a 510(k) summary for a new antimicrobial addition.
9. How the Ground Truth for the Training Set Was Established
The document does not specify how the ground truth for any potential training set was established. Similar to point 8, this information pertains to the internal development of the Phoenix system's core algorithms, which predates the specific 510(k) submission for the addition of a new antimicrobial agent like Cefpodoxime. For AST systems, the ground truth for algorithmic development would also rely on established reference methods like CLSI broth microdilution.
§ 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.”