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The BD Phoenix™ Automated Microbiology System is intended for in vitro quantitative determination of antinicrobial susceptibility by minimal inhibitory concentration (MIC) of most Gram-negative aerobic and anultative an ourobic bacteria isolates from pure culture for Enterobacieriaceae 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 the addition of the antimicrobial agent nitrofurantoin at the concentration of 4 - 128 ug/mL to Gram-Positive ID/AST or AST only BD Phoenix panels. Nitrofirantoin 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:

Staphylococcus aureus Enterococci (e.g., Enterococcus faecalis)

Active In Vitro

Coagulase-negative staphylococci (including Staphylococcus epidermidis and Staphylococcus saprophyticus)

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 or 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. Phoenix panels are inoculated with a specified organism density and placed into the instrument.

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℃. 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. R or N (susceptible, intermediate, resistant or not susceptible).

Here's a breakdown of the acceptance criteria and study details for the BD Phoenix™ Automated Microbiology System - Nitrofurantoin, based on the provided 510(k) summary:

1. Table of Acceptance Criteria and Reported Device Performance

Note: While specific numerical acceptance criteria for EA and CA are not explicitly listed in this document, the FDA guidance for AST systems typically expects high agreement (e.g., >90%). The presented data demonstrates performance exceeding these general expectations.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size for Test Set: 979 isolates were tested for Essential Agreement (EA) and Category Agreement (CA) for Nitrofurantoin.
• Data Provenance: The isolates included "Clinical, stock and challenge isolates" tested across "multiple geographically diverse sites across the United States." The study design indicates a prospective approach for collecting clinical isolates for comparison, and a retrospective or curated approach for stock and challenge isolates.

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

The document does not explicitly state the number or qualifications of experts used to establish the ground truth. However, the ground truth was established by a "CLSI reference broth microdilution method" which implies adherence to standardized laboratory procedures, performed by trained laboratory personnel, rather than expert interpretation of images or observations.

4. Adjudication Method for the Test Set

The document does not mention an adjudication method in the traditional sense, as the comparison is against an objective reference method (CLSI broth microdilution) rather than subjective expert interpretations that would require adjudication.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No, an MRMC comparative effectiveness study was not performed. This study focuses on the performance of an automated diagnostic system compared to a reference method, not on human reader performance with or without AI assistance.

6. Standalone (Algorithm Only) Performance Study

Yes, a standalone performance study was done. The BD Phoenix™ Automated Microbiology System operates as an automated device ("algorithm only") to determine antimicrobial susceptibility. The study compared the results generated by this automated system directly against the CLSI reference broth microdilution method without human intervention in the interpretation process of the Phoenix system's output.

7. Type of Ground Truth Used

The type of ground truth used was the CLSI reference broth microdilution method. This is a laboratory-based, gold-standard method for determining antimicrobial susceptibility, providing a highly objective and quantitative measure (Minimum Inhibitory Concentration - MIC).

• For Clinical Isolates: Phoenix System results were compared to the results obtained from the CLSI reference broth microdilution method.
• For Challenge Isolates: Phoenix System results were compared to "expected results," which would also be derived from the CLSI reference method or other validated methods.

8. Sample Size for the Training Set

The document does not explicitly state the sample size used for the training set. It describes the evaluation of the performance of the device, not the development or training of its underlying algorithms.

9. How the Ground Truth for the Training Set Was Established

Since the document does not mention a training set or algorithm development (it's focused on performance evaluation against a reference), it does not describe how ground truth for a training set was established. The "ground truth" referenced throughout the performance evaluation is the CLSI reference broth microdilution method.

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