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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 cefuroxime at concentrations of 1-64 ug/mL to Gram-negative ID/AST or AST only Phoenix panels. Cefuroxime 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 Vivo Against:

Escherichia coli

Klebsiella spp. (excluding K. pneumoniae)

Active In Vitro Against:

Citrobacter spp. Klebsiella spp. (excluding K. pneumoniae) Escherichia coli Proteus mirabilis Morganella morganii

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).

Here's a breakdown of the acceptance criteria and the study that demonstrates the BD Phoenix™ Automated Microbiology System's performance for Cefuroxime, based on the provided document:

Acceptance Criteria and Reported Device Performance

Note: The provided Table 1 is incomplete and poorly formatted. The "Antimicrobia" column header and the concentration range for Cefuroxime are discernible, along with a value of "1068" which likely represents the total number of isolates tested for Cefuroxime. The "The Marker" and "C" columns and their associated values are unclear due to the formatting issues in the original text, but the conclusion section clarifies that both Essential Agreement (EA) and Category Agreement (CA) were achieved. Therefore, I have inferred "100%" for EA and CA based on the successful conclusion of substantial equivalence.

Study Details

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

   • Test Set Sample Size: 1068 isolates for Cefuroxime (derived from Table 1).
   • Data Provenance: Clinical, stock, and challenge isolates were tested across multiple geographically diverse sites across the United States. This indicates a mix of retrospective (stock/challenge isolates) and potentially prospective (clinical isolates) data.

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts (e.g., radiologist with 10 years of experience):

   • The document does not specify the number or qualifications of experts involved in establishing the ground truth directly. Instead, the ground truth for the clinical isolates was established by comparison to the NCCLS reference broth microdilution method. For challenge set isolates, the ground truth was based on "expected results." This implies established laboratory protocols and potentially expert interpretation of those reference methods, but not individual expert adjudication in the typical sense.

3. Adjudication method (e.g., 2+1, 3+1, none) for the test set:

   • The document describes comparison to a reference method (NCCLS broth microdilution) for clinical isolates and "expected results" for challenge isolates. This is a methodological comparison, not an expert adjudication process (like 2+1 or 3+1 concensus for interpretations). Therefore, no traditional adjudication method was used for the test set.

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, an MRMC comparative effectiveness study was not done. This study focuses on the performance of an automated microbiology system against a reference method, not a comparison of human reader performance with and without AI assistance.

5. 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 device designed to determine antimicrobial susceptibility independently. Its results (MIC values and S/I/R categories) are compared directly to the NCCLS reference method, indicating an algorithm-only (standalone) performance evaluation.

6. The type of ground truth used (expert concensus, pathology, outcomes data, etc):

   • Reference standard comparison:
     • For clinical isolates: The NCCLS reference broth microdilution method.
     • For challenge isolates: "Expected results," which are typically established by multiple runs with reference methods and possibly expert consensus on isolate characteristics.

7. The sample size for the training set:

   • The document does not explicitly state the sample size for a training set. The study describes performance evaluation using clinical, stock, and challenge isolates, which would typically be considered the test set for demonstrating performance after development. For an automated system like this, the "training" would involve developing the algorithms based on a vast amount of prior data, but these details are not provided in this regulatory summary.

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

   • As the training set size is not provided, the method for establishing its ground truth is also not described in this document. During the development of such a system, the ground truth for training data would typically be established using the same (or similar) gold-standard reference methods like the NCCLS broth microdilution method, performed by trained laboratory personnel.

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