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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 and Enterococcus.

This premarket notification is for the antimicrobial agent gentamicin at concentrations of 0.25-16 ug/mL to Gram Negative ID/AST or AST only Phoenix panels. Gentamicin 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 Against:

Aerobic Gram-negative microorganisms

Citrobacter species Enterobacter species Escherichia coli Klebsiella species Proteus species (indole-positive and indole-negative) Pseudomonas aeruginosa Serratia 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 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).

1. Acceptance Criteria and Reported Device Performance:

2. Sample size used for the test set and the data provenance:

• Test Set Sample Size: 7751 isolates were used for Essential Agreement (EA) calculation and 975 isolates for Category Agreement (CA).
• Data Provenance: The isolates were tested across multiple geographically diverse sites across the United States. The study included clinical, stock, and challenge isolates. This indicates the data is prospective and collected from the USA.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

The document does not explicitly state the number or qualifications of experts used to establish the ground truth. It refers to the "NCCLS reference broth microdilution method" as the gold standard for clinical isolates and "expected results" for challenge isolates. The NCCLS (now CLSI) method is a standardized laboratory procedure, implying trained microbiologists would perform and interpret these reference tests, but specific expert details are not provided.

4. Adjudication method for the test set:

The document does not describe an adjudication method for discrepancies between the Phoenix System results and the reference method. Instead, it measures "Essential Agreement" (agreement within one two-fold dilution) and "Category Agreement" (agreement on S, I, or R interpretation) directly against the reference results. This suggests a direct comparison rather than an adjudication process involving multiple expert reviewers.

5. If a multi-reader, multi-case (MRMC) comparative effectiveness study was done:

No, a multi-reader, multi-case (MRMC) comparative effectiveness study was not done. The study compares the automated device's performance against a reference laboratory method, not against human readers with and without AI assistance.

6. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done:

Yes, a standalone performance study was done. The BD Phoenix™ Automated Microbiology System is an automated system that provides identification and antimicrobial susceptibility testing. The reported performance (EA and CA) refers to the system's output (algorithm only) compared to the reference standard. Human input is limited to preparing the inoculum and loading the panels, not interpreting the results generated by the system.

7. The type of ground truth used:

• For clinical isolates: The ground truth was established by the NCCLS reference broth microdilution method (NCCLS M7). This is a standardized laboratory method considered the gold standard for antimicrobial susceptibility testing.
• For challenge isolates: The ground truth was "expected results." This typically refers to results pre-determined by the manufacturer or expert laboratories for control strains.

8. The sample size for the training set:

The document does not specify a separate training set or its sample size. The study describes "Clinical, stock and challenge isolates" tested to demonstrate performance, implying these might have served as a validation/test set. For a device like the Phoenix System, the "training" (development and calibration) would likely involve extensive in-house testing and refinement before clinical studies, but this information is not provided in a 510(k) summary.

9. How the ground truth for the training set was established:

As no specific training set is mentioned, the method for establishing its ground truth is not described. However, given the nature of AST devices, the development and calibration of the system would rely on established microbiological methods (like the NCCLS method) for determining reference MICs and interpretations for a wide range of organisms and antimicrobial agents.

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