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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, Enterococcus, and Streptococcus.

This premarket notification is for additional organism groups and BD Phoenix™ Automated Microbiology System with erythromycin (0.0625-8 µg/mL), quinupristin/dalfopristin (0.25-4 ug/mL), and chloramphenicol (1-32 µg/mL) on ID/AST or AST only Phoenix panels.

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 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 the breakdown of the acceptance criteria and study information for the BD Phoenix™ Automated Microbiology System, based on the provided text:

Acceptance Criteria and Device Performance

The acceptance criteria are implied by the statement: "The BD Phoenix™ Automated Microbiology System demonstrated substantially equivalent performance when compared with the CLSI reference broth microdilution method." The specific quantitative acceptance criteria are that Essential Agreement (EA) and Category Agreement (CA) should be high, with the reported performance values being the evidence of meeting these criteria. The FDA Draft guidance document, "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA," February 5, 2003, is cited as the standard for evaluation.

Note: The document states that intra-site reproducibility was greater than 90% and inter-site reproducibility was greater than 95% for the isolates tested in the reproducibility study. While these are strong performance metrics, the primary performance for regulatory approval seems to hinge on EA and CA compared to the reference method.

Study Details

2. Sample Size and Data Provenance (Test Set)

• Sample Size (Test Set):
  • Erythromycin: 1395 isolates
  • Quinupristin/dalfopristin: 2019 isolates (for EA), 1500 isolates (for CA)
  • Chloramphenicol: 1447 isolates
• Data Provenance: Clinical, stock, and challenge isolates were tested. The study was conducted "across multiple geographically diverse sites across the United States," indicating a multi-center, U.S.-based origin. It includes both "clinical isolates" (which are typically prospective or recently retrospective) and "stock and challenge isolates" (which are curated laboratory strains).

3. Number of Experts and Qualifications for Ground Truth (Test Set)

• The document does not explicitly state the number of experts used or their specific qualifications.
• The ground truth for clinical isolates was established by the "CLSI reference broth microdilution method." This method itself is a standardized laboratory procedure, and implicitly relies on expert microbiologists and technicians to perform and interpret it correctly.
• For "challenge set isolates," the ground truth was "expected results," which would also be determined by established reference methods or expert consensus from culture collections.

4. Adjudication Method (Test Set)

• The document does not explicitly describe an adjudication method in the traditional sense (e.g., 2+1 reader consensus).
• The comparison is made between the Phoenix System results and the "CLSI reference broth microdilution method" results. Discrepancies would likely be investigated by re-testing or thorough review of the reference method results by laboratory personnel. However, a formal multi-reader adjudication process for discrepancies is not detailed.

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

• No, an MRMC comparative effectiveness study was not done. This study focuses on the standalone performance of the automated system against a reference laboratory method, not on how human readers perform with or without AI assistance.

6. Standalone Performance Study

• Yes, a standalone study was performed. The entire "Clinical Studies" section describes the performance of the BD Phoenix™ Automated Microbiology System (algorithm only) compared to the CLSI reference broth microdilution method. The reported Essential Agreement and Category Agreement percentages are measures of this standalone performance.

7. Type of Ground Truth Used

• Reference Method/Expert Consensus (implicit): For clinical isolates, the ground truth was established by the "CLSI reference broth microdilution method." This is considered a gold standard laboratory method. While not explicitly "expert consensus" in the sense of multiple human readers interpreting an image, the CLSI method itself is defined by expert microbiologists and its execution requires trained personnel.
• Expected Results: For "challenge set isolates," the ground truth was "expected results," which implies pre-defined, known results based on established methods for these control strains.

8. Sample Size for the Training Set

• The document does not explicitly state the sample size for the training set. The description details studies for validation of the device's performance against reference methods with specific antimicrobial agents. The underlying algorithms for the Phoenix system would have been developed and trained using a separate dataset over time, but details of that specific training set are not provided in this 510(k) summary focused on adding new antimicrobial agents.

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

• As the training set details are not provided, the method for establishing its ground truth is also not described in this document. It can be inferred that earlier development of the Phoenix system would have involved extensive data collection and the use of reference methods (like CLSI broth microdilution) to establish ground truth for training bacterial identification and antimicrobial susceptibility algorithms.

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