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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 belonging to the genera Staphylococcus, Enterococcus, and Streptococcus.

This premarket notification is for the addition of the antimicrobial agent tetracycline at concentrations of 0.0625 - 16 µg/mL to the Streptococcus ID/AST or AST only Phoenix panels. Tetracycline has been shown to be active in vitro and in clinical infections against Streptococcus species, including S. pneumoniae 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. For testing Streptococcus species 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-S Broth used for performing AST tests only. ●
• BD Phoenix AST-S 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 veliminarily 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. Mercurements 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, R or N (susceptible, intermediate, resistant or not susceptible).

Here's a breakdown of the acceptance criteria and study details for the BD Phoenix™ Automated Microbiology System for Tetracycline, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are implied by the "Essential Agreement (EA)" and "Category Agreement (CA)" metrics, which are industry standards for AST system performance compared to a reference method. While explicit percentage targets for acceptance aren't stated directly in the summary, regulatory guidance documents typically require high percentages for substantial equivalence. The reported performance demonstrates strong agreement.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size (Test Set):
  • For Essential Agreement (EA): n = 1268 isolates
  • For Category Agreement (CA): n = 1568 isolates
  • For Reproducibility (Intra- and Inter-site): A panel of streptococcal isolates. (Specific number not provided in the summary, but tested in triplicate on three different days at three sites).
• Data Provenance:
  • Clinical, stock, and challenge isolates were tested.
  • Across multiple geographically diverse sites (implies prospective and multi-site data collection).

3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications of Those Experts

This document does not specify the number or qualifications of experts used to establish the ground truth. It states that the Phoenix System results were compared to the CLSI reference broth microdilution method for clinical isolates, and to expected results for challenge set isolates. The CLSI method itself is a standardized, expert-approved methodology for AST, but not individual experts for this specific study.

4. Adjudication Method for the Test Set

The document does not describe an explicit adjudication method (e.g., 2+1, 3+1). Instead, the performance is assessed by comparing the Phoenix System results directly to the established CLSI reference broth microdilution method results or "expected results" for challenge isolates. Discrepancies would be identified through this comparison, but the process for resolving disagreements between the device and the reference standard, if any, is not detailed.

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 system for antimicrobial susceptibility testing, not an imaging or diagnostic aid that typically involves human "readers" interpreting results that AI would assist with. The comparison is between an automated system's performance and a standard reference method.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

Yes, this study is inherently a standalone performance evaluation. The BD Phoenix System is an automated device designed to autonomously perform identification (ID) and antimicrobial susceptibility testing (AST). The performance metrics (EA, CA, Reproducibility) directly reflect the algorithm's output compared to a reference standard, without human intervention in the interpretation process of the device's results.

7. The Type of Ground Truth Used

The ground truth used was:

• CLSI reference broth microdilution method: For clinical isolates. This is a standardized, internationally recognized laboratory method considered the gold standard for antimicrobial susceptibility testing.
• Expected results: For challenge isolates. This implies known or pre-determined susceptibility profiles for these specific strains, often used to test the device's ability to accurately identify known resistant or susceptible patterns.

8. The Sample Size for the Training Set

The document does not provide any information regarding the sample size used for the training set. This is typical for a 510(k) submission for an established automated system, where the focus is on the validation of a specific antimicrobial agent addition rather than the initial development of the core algorithm.

9. How the Ground Truth for the Training Set Was Established

The document does not provide any information on how the ground truth for any potential training set was established. As mentioned above, the submission focuses on validating the performance for the addition of a new antimicrobial agent (Tetracycline) to an already cleared system.

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