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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 the antimicrobial susceptibility by minimal inhibitory concentration (MIC) of most Gram-negative Enterobacteriaceae and Non-Enterobacteriaceae facultative anaerobic bacteria isolates from pure culture belonging to the genera Staphylococcus, Enterococcus and Streptococcus.

This premarket notification is for the addition of the antimicrobial agent vancomycin at concentrations of 0.0625-32 µg/mL to the Streptococcus ID/AST or AST only Phoenix Panels. Vancomycin has been shown to be active in vitro and in clinical infections against: Streptococci, including S. pyogenes, S. pneumoniae (including penicillin-resistant strains), S. agalactiae, S. bovis and the viridans group.

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. For testing streptococci species 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-S Broth used for performing AST tests only.
• BD Phoenix AST-S 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, R or N (susceptible, intermediate, resistant or nonsusceptible).

Here's a summary of the acceptance criteria and study details for the BD Phoenix™ Automated Microbiology System for Vancomycin, based on the provided text:

Acceptance Criteria and Device Performance

Acceptance Criteria for Essential Agreement (EA) and Category Agreement (CA):
The FDA Draft guidance document, "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA," February 5, 2003, outlines the performance criteria for Essential Agreement (EA) and Category Agreement (CA). While the exact numerical thresholds for acceptance are not explicitly listed in the provided text, the study's goal was to demonstrate "substantially equivalent performance" to the CLSI reference broth microdilution method. Historically, for AST devices, this typically implies high percentages for both EA and CA (e.g., >90-95%). The provided study results are compared against these implicit standards.

Note: The reported CA for Vancomycin is presented as "12 1" and "11.0" which is an OCR error. Based on the EA result of 98.2% and the intent to show substantial equivalence, the CA would also be expected to be very high, likely in a similar range. Without the correct parsing for the table, the precise CA value is not available. However, the conclusion states that the data demonstrates substantial equivalence, indicating that all relevant criteria were met.

Study Details

1. Sample Size Used for the Test Set and Data Provenance:

   • Test Set Size:
     • For Accuracy (Essential and Category Agreement): 1939 isolates for Vancomycin (as per the "EA (n)" column in the "Accuracy" table).
     • For Reproducibility: A "panel of streptococcal isolates" was used. The exact number is not specified but the study was conducted in triplicate on three different days.
   • Data Provenance: Clinical, stock, and challenge isolates were tested across multiple geographically diverse sites across the United States. This indicates a prospective and multi-site collection process within the US.

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

   • The ground truth for clinical isolates was established by comparing Phoenix System results to the CLSI reference broth microdilution method.
   • For challenge set isolates, the Phoenix System results were compared to "expected results."
   • No human experts were used to establish the primary ground truth. The CLSI reference method is an established laboratory standard.

3. Adjudication Method for the Test Set:

   • Not applicable as the ground truth was based on a reference laboratory method (CLSI broth microdilution) rather than expert review requiring adjudication.

4. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study:

   • No MRMC comparative effectiveness study was done. This device is an automated system providing quantitative results (MIC values) and categorical interpretations (S, I, R, N), not an imaging or diagnostic aid that humans interpret. Therefore, the concept of "human readers improve with AI vs without AI assistance" does not apply.

5. Standalone Performance:

   • Yes, a standalone performance study was done. The entire study describes the performance of the algorithm only (the BD Phoenix Automated Microbiology System) against a reference standard (CLSI broth microdilution method). The system is fully automated, as indicated by its name and description.

6. Type of Ground Truth Used:

   • Reference Method: The CLSI reference broth microdilution method was used as the ground truth for clinical isolates.
   • Expected Results: For challenge set isolates.

7. Sample Size for the Training Set:

   • The document does not provide details on a specific training set or its size. This type of device relies on established biological and chemical principles encoded into an algorithm, not typically a "machine learning" training process in the modern sense that would require a distinct, large training dataset. The development would involve internal validation and optimization, but distinct "training set" and "test set" reporting in the ML context is not present here.

8. How Ground Truth for the Training Set Was Established:

   • Not explicitly described, as the document doesn't detail a distinct training set. The system's underlying principles for identifying bacterial growth and MIC determination are based on well-established microbiological methods and redox indicators.

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