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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 ceftazidime at concentrations of 0.5-64 µg/mL to gram-negative ID/AST or AST only Phoenix panels. Ceftazidime 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:
Citrobacter spp., excluding Citrobacter freundii
Enterobacter spp., including Enterobacter cloacae, and Enterobacter aerogenes
Escherichia coli
Klebsiella spp., including Klebsiella pneumoniae
Proteus mirabilis
Proteus vulgaris
Pseudomonas spp., including Pseudomonas aeruginosa
Serratia spp.

The BD Phoenix Automated Microbiology System (Phoenix System) is an automated system for the in vitro diagnostic 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 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 bacterial turbidity are used in the determination of MIC values. Each Phoenix 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 degrees C. The instrument monitors the growth in each well 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).

The provided text describes the performance of the BD Phoenix™ Automated Microbiology System when testing the antimicrobial agent Ceftazidime against gram-negative organisms.

Here's an analysis of the acceptance criteria and study details:

1. A table of acceptance criteria and the reported device performance:

The study refers to the FDA guidance document "Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA," February 5, 2003, for establishing the acceptance criteria. The performance is assessed using Essential Agreement (EA) and Category Agreement (CA).

Note: While the exact numerical acceptance criteria for EA and CA are not explicitly stated in the provided text, they are generally established to be high (e.g., above 90%) for substantial equivalence in AST device submissions according to FDA guidance documents. The document states that performance was "substantially equivalent as outlined in the FDA guidance document."

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

• Test Set Sample Size:
  • Clinical Isolates: The table shows n = 1706 for Ceftazidime, which likely represents the total number of clinical isolates tested.
  • Reproducibility Studies: "one lot of gram-negative Phoenix panels containing this antimicrobial agent and associated reagents" was tested across three different days for intra- and inter-site reproducibility. The exact number of isolates used in these reproducibility studies is not explicitly stated, but they involved "gram-negative isolates."
• Data Provenance: "Clinical, stock and challenge isolates were tested across multiple geographically diverse sites across the United States." This indicates prospective and retrospective data (clinical isolates, stock and challenge isolates) from multiple locations within the United States.

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

The text does not specify the "number of experts" or their "qualifications." The ground truth was established by the NCCLS reference broth microdilution method, which is a standardized laboratory procedure rather than an expert consensus based on individual human interpretation.

4. Adjudication method for the test set:

Not applicable. The ground truth was based on the NCCLS reference broth microdilution method, which is a quantitative laboratory test. There was no need for human expert adjudication in the context of interpreting the reference method results.

5. 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:

Not applicable. This device is an automated microbiology system and not an AI-assisted diagnostic tool that human readers would use. The comparison is between the automated system's performance and a standardized reference laboratory method, not human reader performance.

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

Yes, a standalone performance study was done. The entire study focuses on the performance of the BD Phoenix™ Automated Microbiology System (an automated device/algorithm) in determining antimicrobial susceptibility. Its results are compared directly to the NCCLS reference method without human interpretation being part of the Phoenix system's performance evaluation.

7. The type of ground truth used:

The ground truth used was the NCCLS reference broth microdilution method, which is a standardized, established laboratory test for antimicrobial susceptibility. This is a reference standard method rather than expert consensus, pathology, or outcomes data.

8. The sample size for the training set:

The document does not explicitly mention a "training set" or its size. This type of submission (510(k) for an AST system) typically focuses on the device's validation against a reference method rather than describing an AI model's training process. The system is likely based on established principles of bacterial growth and redox indicators, not a machine learning model that requires a discrete training set in the conventional sense.

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

Not applicable, as a distinct training set (in the machine learning sense) is not described or implied for this automated system. The device's underlying principles are based on known biological and chemical reactions for bacterial growth and metabolism.

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