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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 Grampositive bacteria of human origin.

This premarket notification is for the addition of the antimicrobial agent doxycycline at concentrations of (0.25 - 16 ug/mL) to Gram-positive ID/AST or AST only Phoenix panels. Doxycycline 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*

• Doxycycline is not the drug of choice in the treatment of any type of staphylococcal infection.

Active In Vitro
Enterococcus group (Streptococcus faecalis and Streptococcus faecium)

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 summary of the acceptance criteria and the study that proves the device meets them, based on the provided text:

Device: BD Phoenix™ Automated Microbiology System - Doxycycline (0.25 - 16 ug/mL)

Intended Use: 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 specific submission adds Doxycycline (0.25 - 16 ug/mL) to Gram-positive ID/AST or AST only Phoenix panels.

1. Table of Acceptance Criteria and Reported Device Performance

Note: The exact numerical thresholds for Essential Agreement (EA) and Category Agreement (CA) as stated in the FDA guidance document "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA", March 5, 2007, are not explicitly provided in this 510(k) summary but are understood to be the acceptance criteria. The document states that the system "has demonstrated substantially equivalent performance" based on these metrics.

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

• Sample Size for Test Set:
  • Site Reproducibility: A "panel of Gram-positive isolates" was tested. The exact number of isolates is not specified, but each isolate was tested in triplicate on three different days at each of three sites.
  • Clinical Studies: "Clinical, stock and challenge isolates" were tested. The overall number of isolates (clinical, stock, and challenge combined) used for performance evaluation (EA and CA) is summarized in a table, but the specific breakdown is not provided. The table heading "e of RD Phoenix System for Gram-Positive Organisms by Drug" does not contain numbers, but implies that data was presented.
• Data Provenance: "Multiple geographically diverse sites across the United States" for clinical studies. Retrospective/Prospective information is not explicitly stated, but "clinical isolates" usually refers to samples collected from patients, which can be either. "Stock and challenge isolates" are typically laboratory-maintained strains.

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

The document does not mention the use of experts to establish a "ground truth" through consensus for the test set. Instead, the ground truth for clinical isolates was established by comparison to the CLSI (formerly NCCLS) reference broth microdilution method. For challenge isolates, they were compared to "expected results," which would be predetermined ground truth for those specific strains.

4. Adjudication Method for the Test Set

No explicit adjudication method (like 2+1 or 3+1) is described. The device's results (MICs and category interpretations) were directly compared to the results from the CLSI reference broth microdilution method or "expected results" for challenge isolates. Discrepancies would be evaluated against the definitions of Essential Agreement and Category Agreement.

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

No Multi-Reader Multi-Case (MRMC) comparative effectiveness study was mentioned. This type of study is more common for imaging devices where human interpretation is a primary component. For an automated AST system, the focus is on the agreement with a standardized reference method rather than human improvement with assistance.

6. Standalone (Algorithm Only Without Human-in-the-Loop) Performance Study

Yes, the primary study described is a standalone performance evaluation. The BD Phoenix™ Automated Microbiology System's performance was assessed by comparing its automated results (MIC values and category interpretations) against a reference method (CLSI broth microdilution) or expected results, without human interpretation of the device's output influencing the direct comparison to the ground truth.

7. Type of Ground Truth Used

• Clinical Isolates: CLSI (formerly NCCLS) reference broth microdilution method.
• Challenge Isolates: "Expected results" (typically pre-established values for these known strains).

8. Sample Size for the Training Set

The document does not explicitly state the sample size for a "training set." This type of 510(k) summary focuses on the validation of the device's performance against a reference standard, not necessarily on detailing the development or training of the internal algorithms. The system likely uses established algorithms and breakpoints, and the studies described are for validation of the performance with the new antimicrobial agent.

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

As no specific training set size is mentioned, the method for establishing its ground truth is also not detailed. However, for such a system, the underlying algorithms for interpreting growth and determining MICs would have been developed and "trained" using extensive datasets of known isolates with their corresponding reference method results, likely following CLSI guidelines.

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