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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 Streptococcus, and Streptococcus.

This premarket notification is for additional organism groups and Tetracycline 0.5-16 µg/mL on the BD Phoenix Automated Microbiology System.

Tetracycline 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:

Gram-negative organisms
Acinetobacter species
Escherichia coli
Enterobacter aerogenes
Klebsiella species
Shigella species

Gram-positive organisms
Staphylococcus aureus

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 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 (MTC) values and category interpretations, S, I, or R (sensitive, intermediate, or resistant).

Here's the detailed breakdown of the acceptance criteria and study findings for the BD Phoenix™ Automated Microbiology System - Tetracycline 0.5-16 µg/mL:

1. Table of acceptance criteria and the reported device performance

Notes on Acceptance Criteria:
The document states that the system "demonstrated substantially equivalent performance when compared with the CLSI reference broth microdilution method" and "has been evaluated as defined in the Fparent guidance document, 'Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA,' February 5, 2003." While specific numerical acceptance criteria for EA and CA are not explicitly stated in the provided text, the FDA guidance document referenced typically requires performance metrics like EA and CA to be above 90% (and often closer to 95% or higher) for a device to be considered "substantially equivalent." Therefore, the reported performance clearly meets these implied acceptance criteria.

2. Sample size used for the test set and the data provenance

• Sample Size for Test Set:
  • Gram-Negative (GN) organisms: 2837 isolates
  • Gram-Positive (GP) organisms: 2040 isolates
• Data Provenance: Clinical, stock, and challenge isolates were tested across multiple geographically diverse sites across the United States. This indicates a prospective collection for at least the clinical isolates, and likely a mix of prospective (clinical) and curated (stock/challenge) data.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts

The document does not specify the number of experts or their qualifications for establishing the ground truth. The ground truth was established by the CLSI reference broth microdilution method. This method is a standardized laboratory procedure, and adherence to this protocol is overseen by laboratory personnel.

4. Adjudication method for the test set

The document does not describe an adjudication method for the test set. The comparison was made directly between the BD Phoenix System results and the CLSI reference broth microdilution method results.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance

No, an MRMC comparative effectiveness study involving human readers and AI assistance was not conducted or described. This device is an automated system for antimicrobial susceptibility testing, not an imaging or diagnostic AI tool designed to assist human readers.

6. If a standalone (i.e. algorithm only without human-in-the loop performance) was done

Yes, a standalone study was done. The entire study evaluated the performance of the BD Phoenix™ Automated Microbiology System as an automated system, comparing its results directly to the CLSI reference broth microdilution method. There is no mention of human input influencing the Phoenix System's determination of susceptibility.

7. The type of ground truth used

The ground truth used was the CLSI reference broth microdilution method. This is a validated, standardized laboratory procedure for determining antimicrobial susceptibility, considered the gold standard in many contexts.

8. The sample size for the training set

The document does not provide information regarding a specific "training set" sample size. For AST systems like the Phoenix, the "training" (or development and calibration) is typically done during the product development phase to establish the algorithms and interpretation rules for the system's measurements (e.g., redox indicator changes, turbidity) to correlate with MIC values and clinical categories. The provided study focuses on the validation of a specific antimicrobial agent (Tetracycline) and organism groups on an already developed system.

9. How the ground truth for the training set was established

The document does not provide information on how the ground truth for the training set (if a distinct training set in the AI/ML sense was used) was established. Given the nature of the device, the system's development would have involved extensive correlation studies with the CLSI reference broth microdilution method and expert microbiological interpretation to establish its internal algorithms and interpretive criteria prior to the specific validation study described.

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