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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 trimethoprim at concentrations of 0.5-16 ug/mL to Gram-negative ID/AST or AST only Phoenix panels. trimethoprim 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
Proteus mirabilis
Klebsiella pneumoniae
Enterobacter species

Active In Vitro Against:
Common urinary tract pathogens with the exception of Pseudomonas aeruginosa

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 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).

The BD Phoenix™ Automated Microbiology System is designed for rapid identification and antimicrobial susceptibility testing (AST) of bacterial isolates. This summary focuses on its performance with the antimicrobial agent Trimethoprim (0.5-16 µg/mL) for Gram-negative organisms.

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for the BD Phoenix System, specifically for Trimethoprim against Gram-negative organisms, are not explicitly stated as numerical targets within the provided text (e.g., "EA must be >90%"). However, the study aims to demonstrate substantial equivalence to the NCCLS reference broth microdilution method. The performance metrics used are Essential Agreement (EA) and Category Agreement (CA). Based on the results provided, the de facto acceptance criteria appear to be:

• Essential Agreement (EA) for Gram-negative Organisms: High percentage (demonstrated as 90.5%).
• Category Agreement (CA) for Gram-negative Organisms: High percentage (demonstrated as 98.7%).
• Site Reproducibility: Overall intra-site reproducibility >90% and inter-site reproducibility >95% for Gram-negative isolates.

2. Sample Size and Data Provenance

• Test Set Sample Size:
  • Clinical Study (Performance): 1856 isolates for the performance metrics (EA and CA).
  • Site Reproducibility: Not explicitly stated as a single number, but a "panel of Gram-negative isolates" was tested in triplicate on three different days at three sites, using one lot of panels.
• Data Provenance: The clinical studies were conducted across multiple geographically diverse sites across the United States. The data is prospective in nature, comparing the Phoenix System results to a reference method.

3. Number of Experts and Qualifications for Ground Truth

The document does not explicitly state the number or specific qualifications of experts used to establish the ground truth. However, the ground truth for the clinical isolates was established using the NCCLS reference broth microdilution method. This method is a standardized laboratory procedure, performed by trained laboratory personnel, rather than relying on individual expert interpretation of images or observations.

4. Adjudication Method for the Test Set

The document does not describe an adjudication method in the context of multiple readers or experts reviewing results. The comparison is made between the BD Phoenix System's automated results and the results from the NCCLS reference method. Discrepancies would likely be investigated through re-testing or confirmation by standard laboratory protocols rather than an adjudication panel.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No multi-reader multi-case (MRMC) comparative effectiveness study was mentioned. The device is an automated system, and the study focuses on the agreement of its automated output with a reference standard, not on how human readers' performance might change with or without AI assistance.

6. Standalone Performance

Yes, a standalone performance study was conducted. The "Clinical Studies" section directly assesses the BD Phoenix System's (algorithm only, with its automated readings) performance by comparing its Essential Agreement (EA) and Category Agreement (CA) to the NCCLS reference broth microdilution method. This evaluates the algorithm's performance without direct human intervention in interpreting the final susceptibility results after the automated reading.

7. Type of Ground Truth Used

The ground truth used for the clinical isolates was the NCCLS reference broth microdilution method. For the "Challenge set isolates," the Phoenix System results were compared to "expected results," which are typically pre-determined and validated results for known strains.

8. Sample Size for the Training Set

The document does not explicitly mention a separate training set or its sample size. The description focuses on the evaluation of the device against reference methods. It's plausible that the underlying algorithms were developed and trained using various data, but this information is not provided in this specific submission summary.

9. How Ground Truth for the Training Set Was Established

Since a training set is not explicitly mentioned, the method for establishing its ground truth is also not provided. The performance evaluation relies on comparing the device's output to established reference methods for clinical and challenge isolates.

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