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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.

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 Enterococcus.

This premarket notification is for the addition of the antimicrobial agent vancomycin at concentrations of 0.5-32 µg/mL to Gram Positive ID/AST or AST only Phoenix panels. Vancomycin 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 species
Enterococcus species

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 isolation 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℃. 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 an analysis of the provided text, focusing on the acceptance criteria and study details for the BD Phoenix™ Automated Microbiology System for Vancomycin:

The document describes the performance evaluation of the BD Phoenix™ Automated Microbiology System when testing the antimicrobial agent Vancomycin against Gram-positive organisms.

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are implied by the comparison to the NCCLS reference broth microdilution method and the FDA's "Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices." Specifically, Essential Agreement (EA) and Category Agreement (CA) are the key metrics. While explicit numeric targets for "acceptance criteria" are not given in the provided text as "acceptance criteria," the study results demonstrate performance relative to these criteria.

Note: The exact numerical acceptance thresholds for EA and CA are not explicitly stated as "acceptance criteria" in the text but are values against which the device performance is measured in substantial equivalence studies for antimicrobial susceptibility testing. The achieved values (97.7% EA, 99.4% CA) are generally considered very good and acceptable for such devices.

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

• Sample Size for Test Set: 1981 isolates (as indicated by 'n=1981' for both EA and CA).
• Data Provenance: Clinical, stock, and challenge isolates were tested. The testing was conducted across multiple geographically diverse sites across the United States. The study is prospective in nature as it involved collecting and testing isolates specifically for this evaluation.

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

The document does not specify the number of experts or their qualifications for establishing the ground truth. It states that:

• "Phoenix System results for Challenge set isolates were compared to the expected results."
• "Phoenix System results for clinical isolates were compared to the results obtained from the NCCLS reference broth microdilution method."

The "NCCLS reference broth microdilution method" is the gold standard for antimicrobial susceptibility testing, and its results are considered the ground truth. While performing this method requires expert technicians following standardized protocols, the document doesn't detail external expert review or consensus for the ground truth itself, as the method is inherently the "expert" ground truth.

4. Adjudication Method for the Test Set

The document does not describe an explicit adjudication method for discrepancies between the Phoenix System and the NCCLS reference method. The comparison focused on calculating Essential Agreement and Category Agreement based on the direct results. It's common in AST studies to have a predefined method for resolving major discrepancies (e.g., very major errors), but this specific detail is not provided.

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

No, an MRMC comparative effectiveness study was not done. This study focuses on a standalone device performance comparison against a reference method, not on human reader performance with or without AI assistance. The device in question is an automated system for susceptibility testing, where the output is directly interpreted (S, I, R) by the system itself based on observed growth, rather than by human readers interpreting images or complex data fields with AI assistance.

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

Yes, a standalone study was performed. The entire evaluation described is a standalone performance assessment. The BD Phoenix™ Automated Microbiology System is an automated device designed to autonomously perform susceptibility testing and report results (MIC values and categories of S, I, R) without direct human intervention in the interpretation process once the panel is loaded. Its results were directly compared to the NCCLS reference method.

7. Type of Ground Truth Used

The ground truth used was the NCCLS reference broth microdilution method for clinical isolates and "expected results" for challenge isolates. The NCCLS method is widely recognized as the gold standard for antimicrobial susceptibility testing.

8. Sample Size for the Training Set

The document does not specify a sample size for the training set. Antimicrobial susceptibility testing devices like the BD Phoenix™ are often developed using a large historical dataset for algorithm training and refinement during product development. The current document focuses on the validation study for a specific antimicrobial agent (Vancomycin) addition to an existing system, not the initial development or training phase of the core algorithm.

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

As the document does not mention the training set size, it also does not explicitly describe how the ground truth for the training set was established. However, based on industry standards for such devices, it is highly probable that the ground truth for any training data (if new training was done for Vancomycin, or for the core system development) would have been established using similar reference methods like the NCCLS broth microdilution method, or other accepted standard methods appropriate for the specific organisms and antimicrobials.

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