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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 gram-positive aerobic and facultative anaerobic bacteria isolates from pure culture belonging to the genera Staphylococcus and Enterococcus.

This premarket notification is for the addition of the antimicrobial agent cefotetan at concentrations of 2-64 µg/mL to the gram-negative ID/AST or AST only Phoenix panels. Cefotetan 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.

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 study details for the BD Phoenix™ Automated Microbiology System - Cefotetan 2-64 µg/mL, based on the provided text:

1. Acceptance Criteria and Reported Device Performance

2. Sample Size and Data Provenance

• Sample Size for Test Set: The document mentions a "panel of gram-negative isolates" was used. The exact number of isolates is not explicitly stated.
• Data Provenance: Not explicitly stated, but given the context of a 510(k) submission to the FDA in the US, it's highly likely the studies were conducted in the US. The study involved "three sites," implying a prospective data collection directly for this validation.

3. Number of Experts and Qualifications for Ground Truth

• The document describes the NCCLS reference broth microdilution method as the comparative "ground truth." This is a standardized laboratory procedure, not an assessment by human experts in the traditional sense of image or clinical interpretation. Therefore, the concept of "experts" to establish ground truth in this context is not directly applicable. The method itself is the gold standard.

4. Adjudication Method

• None (as traditionally understood for human interpretation). The comparison is against a standardized laboratory reference method (NCCLS broth microdilution), which has established protocols for interpretation.

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

• No. This type of study is not applicable as the device is an automated microbiology system for determining antimicrobial susceptibility (MIC values and categories), not a diagnostic imaging aid for human readers.

6. Standalone (Algorithm Only) Performance

• Yes. The entire study described evaluates the standalone performance of the BD Phoenix™ system against the reference method. The system is designed to provide automated interpretations without human intervention in the susceptibility determination process.

7. Type of Ground Truth Used

• Standardized Reference Method: The ground truth was established using the NCCLS reference broth microdilution method (AST panels prepared according to NCCLS M7). This is a widely accepted laboratory standard for antimicrobial susceptibility testing.

8. Sample Size for Training Set

• The provided text does not explicitly state the sample size used for the training set. This document focuses on the validation of a specific antimicrobial agent (Cefotetan) for an existing system. The core system itself would have been developed and trained prior to this specific 510(k) submission.

9. How Ground Truth for Training Set Was Established

• The document does not describe how the ground truth for the training set was established. Similar to the above, the training would have occurred during the initial development of the BD Phoenix System, well before this specific submission for Cefotetan. However, it's safe to assume that a similar approach, involving comparison to established reference methods (like NCCLS broth microdilution), would have been used during the development and training phases of the broader system.

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