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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 antinicrobial 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 tobramycin at concentrations of 0.5-16 ug/mL to Gram Positive ID/AST or AST only Phoenix panels. tobramycin 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 (including penicillin-resistant strains)

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. 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).

This submission describes the BD Phoenix™ Automated Microbiology System for the identification and antimicrobial susceptibility testing of isolates. The summary focuses on the addition of Tobramycin (0.5-16 µg/mL) to the Gram Positive ID/AST or AST only Phoenix panels.

Here's an analysis of the provided information, structured around your requested points:

Acceptance Criteria and Device Performance

The acceptance criteria for the BD Phoenix™ Automated Microbiology System, when compared to the NCCLS reference broth microdilution method, are typically defined by Essential Agreement (EA) and Category Agreement (CA). While specific numerical thresholds for "acceptance" are not explicitly stated as bullet points with percentages, the study's conclusion is that the device demonstrated "substantially equivalent performance" and "overall intra-site reproducibility of greater than 90% and an overall inter-site reproducibility greater than 95%." This implies that the observed EA and CA values, along with reproducibility, met the internal or FDA-specified thresholds for substantial equivalence.

Table 1: Acceptance Criteria and Reported Device Performance

Note: The actual numerical values for EA and CA for Tobramycin are missing from the provided "Table 1" in the extract. The "conclusion" section indicates that the data collected from the studies "demonstrate that testing on the BD Phoenix™ Automated Microbiology System with this antimicrobial agent is substantially equivalent."

Study Details

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

   • Test Set Sample Size: Not explicitly stated in terms of a total number of isolates for the clinical studies. It mentions "a panel of Gram-positive isolates" for reproducibility and "clinical, stock and challenge isolates" for the performance study.
   • Data Provenance: The studies were conducted "across multiple geographically diverse sites across the United States." This indicates the data is from the United States and is likely prospective for the clinical isolates, as they were tested against a reference method. The "challenge set isolates" would also be tested prospectively.

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

   • This information is not provided in the document. The ground truth for AST is typically established by laboratory methods, not expert consensus in the same way an image interpretation might be.

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

   • This concept of "adjudication method" is typically used for subjective interpretations (e.g., grading medical images by multiple readers). For Antimicrobial Susceptibility Testing (AST), the "ground truth" is determined by a chemical/biological reference method, not by human expert agreement. Therefore, none is applicable in the traditional sense. The comparison is against a well-defined reference standard.

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 is for an automated system's performance against a reference method, not for assessing human reader improvement with AI assistance. The BD Phoenix System is an automated device, not an AI assistant for human readers.

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

   • Yes, a standalone study was done. The entire study evaluates the performance of the "BD Phoenix™ Automated Microbiology System" itself (the algorithm and instrument) against the NCCLS reference broth microdilution method. There is no human interaction with the interpretation of the Phoenix system's results for the purpose of the comparison.

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

   • The ground truth used was the NCCLS reference broth microdilution method. This is a laboratory-based, standardized, quantitative microbiological method for determining minimum inhibitory concentrations (MICs). For the "challenge set isolates," the ground truth was "expected results," which would also be derived from established microbiological methods.

7. The sample size for the training set:

   • The document does not provide information about a specific "training set" sample size. The BD Phoenix system is based on established biochemical and susceptibility testing principles, not a machine learning model that requires a distinct training set in the modern AI sense. The development of such systems involves extensive internal validation and optimization, but the concept of a "training set" as defined for contemporary AI models isn't directly applicable or described here.

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

   • As there is no explicit mention of a "training set" in the context of typical machine learning, this information is not provided. The "ground truth" for the development and optimization of the system would have inherently been established through biochemical and microbiological principles and comparison to established reference methods during the device's development phase.

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