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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.

This premarket notification is for the addition of the antimicrobial agent moxifloxacin at concentrations of 0.125-8 µg/mL to Gram Positive ID/AST or AST only Phoenix panels. Moxifloxacin has been shown to be active in viro 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 (methicillin-susceptible strains only)

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 a breakdown of the acceptance criteria and the study details for the BD Phoenix™ Automated Microbiology System Moxifloxacin - GP, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The text explicitly refers to "Essential Agreement (EA)" and "Category Agreement (CA)" as performance metrics. While the specific numerical acceptance criteria (e.g., "EA > 90%") are not explicitly stated, the Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices, March 8, 2000 is referenced, which would likely contain these criteria. For this summary, we will assume the reported performance met the implied acceptance criteria, given the overall conclusion of substantial equivalence.

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

• Test Set Sample Size: The clinical study tested 1242 isolates for Moxifloxacin, as indicated by EA (n) = 1242 and CA (n) = 1242 in Table 1.
• Data Provenance:
  • Country of Origin: United States ("across multiple geographically diverse sites across the United States").
  • Retrospective/Prospective: The text mentions "Clinical, stock and challenge isolates were tested." "Clinical isolates" typically refer to prospectively collected samples from patients, while "stock and challenge isolates" could be a mix of retrospective, well-characterized strains. The study design implies a prospective collection of clinical isolates and possibly predefined challenge strains.

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

The document does not explicitly state the number or qualifications of experts used to establish the ground truth. The ground truth (reference method) was the NCCLS reference broth microdilution method. This method is standardized, and while it requires skilled laboratory personnel to perform, it typically does not involve multiple "experts" in the sense of clinical specialists adjudicating results, but rather adherence to a standardized protocol.

4. Adjudication Method for the Test Set

The document does not describe an adjudication method for the test set in the traditional sense (e.g., 2+1, 3+1 for discrepancies). Instead, the performance of the Phoenix System results (MIC values and categorical interpretations) were directly compared to the results obtained from the NCCLS reference broth microdilution method. Discrepancies would be identified and analyzed based on this comparison, leading to the calculation of Essential Agreement and Category Agreement.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, and Effect Size

No, an MRMC comparative effectiveness study involving human readers with and without AI assistance was not done. This device is an automated microbiology system for antimicrobial susceptibility testing, which replaces or assists traditional manual lab procedures, rather than assisting human readers in interpreting images or complex clinical scenarios directly.

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

Yes, a standalone performance study was done. The entire study focuses on the performance of the "BD Phoenix™ Automated Microbiology System" itself (i.e., the algorithm/automated system) in determining antimicrobial susceptibility. The system takes readings and interprets them "to give an identification of the isolate, minimum inhibitory concentration (MIC) values and category interpretations." This is a direct measurement of the device's algorithmic performance.

7. The Type of Ground Truth Used

The primary ground truth used for the clinical and stock isolates was the NCCLS reference broth microdilution method. For challenge isolates, performance was compared to "expected results," which implies a curated set of known susceptibility profiles for those specific strains. This reference method is a well-established, standardized laboratory method considered the "gold standard" for antimicrobial susceptibility testing.

8. The Sample Size for the Training Set

The document does not provide information about the sample size used for the training set. The focus is on the validation of the existing system with a new antimicrobial agent (Moxifloxacin). The system itself (BD Phoenix) was likely trained or developed using vast amounts of data prior to this specific antimicrobial agent's addition.

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

Since information about the training set is not provided, the method for establishing its ground truth is also not described in this document. During the initial development of the BD Phoenix System, the ground truth for training would almost certainly have been established using similar reference methods (like NCCLS broth microdilution or agar dilution) performed by expert microbiologists, coupled with broad-spectrum organism identification methods.

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