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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-Enteriaceae and most Gram-positive bacteria isolates from pure culture belonging to the genera Staphylococcus, Enterococcus and Streptococcus.

This premarket notification is for the addition of the antimicrobial agent minocycline at concentrations of 1-32 ug/mL to Gram-positive ID/AST or AST only Phoenix panels. Minocycline 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:
Staphylococcus aureus

Active In Vitro Enterococcus species (vancomycin resistant, VRE, VanA, VanB )

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. Phoenix panels are inoculated with a specified organism density and placed into the instrument.

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, 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 Minocycline (1-32 µg/mL), based on the provided text:

Acceptance Criteria and Reported Device Performance

Note: The FDA guidance documents mentioned ("Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems" and "Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices") are the source for these implicit acceptance criteria, even if not explicitly stated with numerical targets in the provided summary table. The reported performance clearly exceeds these generally accepted thresholds.

Study Details

1. Sample sizes used for the test set and the data provenance:

   • Test Set Sample Sizes:
     • Essential Agreement (EA): 1619 isolates
     • Category Agreement (CA): 745 isolates
     • Reproducibility Study: A "panel of Gram-positive isolates" tested in triplicate on three different days at three sites (specific number of isolates not provided, but the number of tests is implied to be significant).
   • Data Provenance: Clinical, stock, and challenge isolates were tested across multiple geographically diverse sites across the United States. This indicates a prospective, multi-center study with a mix of real-world clinical samples and laboratory-controlled stock/challenge samples.

2. 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 or qualifications of experts.
   • Ground truth for clinical isolates was established by the CLSI reference broth microdilution method.
   • Ground truth for challenge isolates was established by "expected results," which typically refers to pre-determined, well-characterized results for those specific strains. This implies expert selection and validation, but specific expert count or qualifications aren't provided.

3. Adjudication method for the test set:

   • The document does not describe an explicit adjudication method in the traditional sense (e.g., 2+1, 3+1) involving human experts reconciling discrepancies.
   • The comparison is directly between the BD Phoenix System's results and the CLSI reference method. Discrepancies would be analyzed for impact on Essential and Category Agreement, but not necessarily "adjudicated" by a committee of experts in a consensus-reaching process for individual cases.

4. 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 was not done.
   • This study evaluates the standalone performance of an automated system (BD Phoenix) against a reference method (CLSI broth microdilution). It does not involve human readers or AI assistance for human readers.

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

   • Yes, a standalone study was done. The BD Phoenix system is an automated device, and its performance was evaluated directly against the CLSI reference method, effectively measuring the algorithm's (system's) performance.

6. The type of ground truth used:

   • For clinical isolates: CLSI reference broth microdilution method. This is a well-established, standardized laboratory reference method for antimicrobial susceptibility testing.
   • For challenge isolates: "Expected results." This implies pre-defined, validated outcomes for specific strains, likely based on extensive prior testing and characterization.

7. The sample size for the training set:

   • The document does not specify a separate "training set" sample size. This is likely because the BD Phoenix System's underlying algorithm (for interpreting growth and generating MICs) was developed and validated prior to this specific premarket notification (which is for the addition of a new antimicrobial agent, Minocycline, to an existing system). The study described here is primarily a validation or test set study for the integrated system with the new agent.

8. How the ground truth for the training set was established:

   • As no specific training set for this particular submission is described, the method for establishing ground truth for any prior training of the BD Phoenix System's general interpretive algorithms is not detailed in this document. It would presumably have involved similar reference methods and extensive characterization of bacterial growth and antimicrobial effects.

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