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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 addition of the antimicrobial agent Oxacillin at concentrations of 0.0625-4 ug/mL to Gram Positive ID/AST or AST only Phoenix panels. Oxacillin 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:

Aerobic Gram-positive microorganisms Staphylococcus spp.

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 isolation equivalent to 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, and resistant).

Here's a breakdown of the acceptance criteria and study details based on your input:

Acceptance Criteria and Device Performance

The provided document describes a premarket notification for the BD Phoenix™ Automated Microbiology System for use with Oxacillin. The acceptance criteria are framed in terms of "Essential Agreement (EA)" and "Category Agreement (CA)" with a reference method.

Table 1: Acceptance Criteria and Reported Device Performance

Note: The exact numerical acceptance criteria for EA and CA are not explicitly stated in the provided text, but these values are typically established in FDA guidance documents for antimicrobial susceptibility devices. The "CAA" column in Table 1 is partially obscured and its precise meaning (e.g., combined EA and CA, or just CA) is not fully clear from this snippet, but it represents the device's performance against the reference for agreement.

Study Details:

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

   • Sample Size: Not explicitly stated as a single number. The study involved "Clinical, stock and challenge isolates." The results are summarized for "all isolates tested" in Table 1, but the total count of isolates for Oxacillin is obscured.
   • Data Provenance: Multiple geographically diverse sites across the United States. Retrospective and Prospective nature is not explicitly stated, but "Clinical isolates" generally imply prospective collection, while "stock and challenge isolates" could be historical or specifically prepared for the study.

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

   • Not applicable/not specified. The ground truth for antimicrobial susceptibility testing (AST) is established through a standardized laboratory method (NCCLS reference broth microdilution method), not by expert consensus on interpretation of images or clinical findings.

3. Adjudication method for the test set:

   • Not applicable. As described above, the ground truth is a laboratory reference method, not an expert-based interpretation requiring adjudication.

4. If a multi reader multi case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:

   • No, a multi-reader multi-case (MRMC) comparative effectiveness study was not done. This study focuses on the performance of an automated microbiology system against a laboratory reference method, not on human reader performance or AI assistance.

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

   • Yes, this study represents a standalone performance evaluation. The BD Phoenix™ Automated Microbiology System is an automated system where the "algorithm" (its internal processing) determines the MIC values and category interpretations, which are then compared to the reference method. While a human might load the panels, the interpretation itself is automated and does not involve human-in-the-loop decision-making during the reading process for comparison purposes in this context.

6. The type of ground truth used:

   • Reference Laboratory Method: The ground truth for antimicrobial susceptibility was established using the NCCLS reference broth microdilution method (AST panels prepared according to NCCLS M7).

7. The sample size for the training set:

   • Not specified. The document describes the validation of a specific AST device rather than the training of an AI algorithm. While the device certainly relies on an "algorithm" for interpretation, the details of its development and any specific "training set" (in the machine learning sense) are not provided. The study is a regulatory submission for device performance comparison.

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

   • Not applicable/not specified. As mentioned, the document doesn't detail the training of a machine learning model but rather the validation of an automated laboratory instrument. The "ground truth" during development would have been based on similar reference microbiology methods.

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