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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 cefepime at concentrations of 0.5-64 ug/mL to Gram-negative ID/AST or AST only Phoenix panels with the removal of the limitations for Proteus species. Cefepime has been shown to be active in vitro against most strains of microorganisms listed below, as described in the FDAapproved package insert for this antimicrobial agent.

Active In Vitro and in Clinical Infections Against:
Enterobacter species
Escherichia coli
Klebsiella pneumoniae
Proteus mirabilis
Pseudomonas aeruginosa

Active In Vitro Against:
Acinetobacter lwoffi
Citrobacter koseri
Citrobacter freundii
Hafnia alvei
Klebsiella oxytoca
Morganella morganii
Pantoea agglomerans
Proteus vulgaris
Providencia rettgeri
Providencia stuartii
Serratia marcescens

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 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 optical density and turbidity are used in the determination of results. The panel configuration contains several antimicrobial agents with a wide range of two-fold doubling dilution concentrations.

The Phoenix panel is a sealed and self-inoculating molded polystyrene tray with 136 micro-wells containing paired 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 in the instrument.

The instrument houses the panels where they are continuously incubated at a nominal temperature of 35 degrees Celsius. The instrument monitors the growth of the organisms in 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 a breakdown of the acceptance criteria and study information for the BD Phoenix™ Automated Microbiology System for Cefepime, based on the provided text:

Acceptance Criteria and Reported Device Performance

Study Details

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

   • Test Set Sample Size: 1384 isolates (as per the "EA (n)" and "CA (n)" columns in Table 1).
   • Data Provenance: Clinical, stock, and challenge isolates from "multiple geographically diverse sites across the United States." This indicates a prospective and real-world data collection approach.

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

   • The document does not specify the number of experts or their qualifications for establishing ground truth. Instead, it compares the device's performance to the "CLSI reference broth microdilution method" or "expected results" for challenge isolates. The CLSI method itself is a standardized laboratory procedure, not an expert consensus per se, though it's assumed to be performed by qualified microbiologists.

3. Adjudication Method for the Test Set:

   • The document does not describe an explicit adjudication method (like 2+1 or 3+1). The comparison is directly between the BD Phoenix System's results and the CLSI reference method or expected results for challenge isolates.

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

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

5. Standalone Performance (Algorithm-only without human-in-the-loop performance):

   • Yes, the performance reported is a standalone performance of the BD Phoenix™ Automated Microbiology System. The device is a fully automated system for determining antimicrobial susceptibility, and its results are directly compared to a reference method.

6. Type of Ground Truth Used:

   • The ground truth for clinical isolates was established using the CLSI (Clinical and Laboratory Standards Institute) reference broth microdilution method.
   • For challenge isolates, the ground truth was "expected results," which typically refers to results obtained from known strains or established testing protocols.

7. Sample Size for the Training Set:

   • The document does not explicitly separate and report a "training set" sample size. The studies described are for validation and comparison to a reference standard, not for the training of a new AI model in the conventional sense. The "clinical, stock, and challenge isolates" described for the performance study are used for evaluating the system, which would likely represent a test set. The system itself is an automated instrument, not a 'learned' AI model in the contemporary sense that requires a distinct training dataset from the user's perspective. Its "knowledge" is embedded in its design and detection algorithms.

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

   • Given that a distinct "training set" in the context of machine learning is not explicitly mentioned or applicable in the way modern AI is developed, the document does not describe how ground truth for a training set was established. The system's underlying methodology (broth microdilution with redox indicator and turbidity measurements) is based on established microbiological principles, not on a machine learning training process with a labeled dataset.

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