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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 norfloxacin at concentrations of 0.25 - 16 µg/mL to Gram Positive ID/AST or AST only Phoenix panels. norfloxacin 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 Staphylococcus epidermidis 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. For each isolation 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).

Acceptance Criteria and Study Details for BD Phoenix™ Automated Microbiology System - Norfloxacin

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for the BD Phoenix™ Automated Microbiology System with Norfloxacin are primarily based on Essential Agreement (EA) and Category Agreement (CA) with the NCCLS reference broth microdilution method.

Note: The document explicitly states that the device demonstrated "substantially equivalent performance when compared with the NCCLS reference broth microdilution method" and was evaluated as defined in the FDA Draft guidance document, "Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices", March 8, 2000. The specific numerical acceptance thresholds were not explicitly stated in this document but are inferred based on typical criteria for such devices and the reported acceptable performance.

2. Sample Size and Data Provenance for the Test Set

• Sample Size for Test Set: 1252 isolates (combined clinical, stock, and challenge isolates, as indicated by 'n' in the performance table).
• Data Provenance:
  • Country of Origin: United States (across multiple geographically diverse sites).
  • Retrospective or Prospective: Not explicitly stated, but the description of testing "clinical, stock and challenge isolates" at "geographically diverse sites" for comparison against a reference method suggests a combination of prospective collection of clinical isolates and possibly retrospective use of stock/challenge isolates.

3. Number of Experts and Qualifications for Ground Truth (Test Set)

• Number of Experts: Not specified.
• Qualifications of Experts: Not specified. The "expected results" for challenge isolates and "reference results" for clinical isolates were used as ground truth, but the method of establishing these specific "expected" or "reference" results (e.g., through expert consensus or a specific laboratory standard) is not detailed. However, it implicitly relies on the established and validated NCCLS reference broth microdilution method.

4. Adjudication Method (Test Set)

• Adjudication Method: Not explicitly stated. The comparison was made against the "NCCLS reference broth microdilution method" or "expected results" for challenge isolates. This suggests a direct comparison to a gold standard, rather than a separate adjudication process among multiple readers/experts for the device's output.

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

• MRMC Study: No, a multi-reader multi-case (MRMC) comparative effectiveness study was not performed. This study focuses on the standalone performance of the automated system compared to a reference method, not on human reader performance with or without AI assistance.

6. Standalone (Algorithm Only) Performance Study

• Standalone Study: Yes, a standalone performance study was conducted. The entire study describes the performance of the "BD Phoenix™ Automated Microbiology System" (the device/algorithm) in determining antimicrobial susceptibility without direct human intervention in the result interpretation process beyond initial setup. The results (EA and CA) are for the system itself.

7. Type of Ground Truth Used (Test Set)

• Type of Ground Truth: The ground truth for the test set was established using the NCCLS reference broth microdilution method for clinical isolates and "expected results" for challenge isolates. The NCCLS method is considered the gold standard for antimicrobial susceptibility testing.

8. Sample Size for the Training Set

• Sample Size for Training Set: Not explicitly stated in the provided text. The document describes the "Clinical Studies" and "Site Reproducibility" which relate to the test and validation of the device, not its initial training. The device is described as having "software," but the nature of that software (e.g., if it uses machine learning requiring a distinct training set) and its specific training data are not detailed.

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

• Ground Truth for Training Set: Not specified. As the document does not detail a distinct training set or machine learning approach, the method for establishing its ground truth (if applicable) is not provided. The system likely relies on programmed algorithms based on established microbiological principles rather than a machine learning model trained on a large dataset with associated ground truth for initial development.

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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 Norfloxacin at concentrations of 0.25-16 ug/mL to Gram Negative ID/AST or AST only Phoenix panels. Norfloxacin 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 freundii Enterobacter aerogenes Enterobacter cloacae Escherichia coli
Klebsiella pneumoniae ssp. pneumoniae Proteus mirabilis Proteus vulgaris Pseudomonas aeruginosa

Active In Vitro Against:
Citrobacter koseri (formerly Citrobacter diversus) Edwardsiella tarda Klebsiella oxytoca Morganella morganii Pantoea agglomerans
Providencia alcalifaciens Providencia rettgeri Providencia stuartii
Pseudomonas fluorescens Pseudomonas stutzeri

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 information for the BD Phoenix Automated Microbiology System with Norfloxacin, based on the provided text:

Acceptance Criteria and Device Performance

The core of the acceptance criteria for this medical device (An Antimicrobial Susceptibility Test System) is its performance compared to a recognized reference method. The primary metrics are Essential Agreement (EA) and Category Agreement (CA).

Note on Acceptance Criteria: The provided document states that the system "demonstrated substantially equivalent performance when compared with the NCCLS reference broth microdilution method" and "has been evaluated as defined in the FDA Draft guidance document, 'Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices', March 8, 2000." This indicates that the acceptance criteria are implicitly those outlined in the referenced FDA guidance document for substantial equivalence, which typically involves achieving certain thresholds for EA and CA. Specific numerical targets for EA and CA for Norfloxacin are not explicitly stated in the summary table but would have been part of the full submission and detailed in the performance data (Table 1, not fully transcribed).

Study Information

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

• Test Set Description: Clinical, stock, and challenge isolates.
• Sample Size: Not explicitly stated as a single number. Table 1, which summarizes the performance, would likely contain the number of isolates tested for Norfloxacin against various gram-negative organisms, but this table is incomplete in the provided text.
• Data Provenance: Multiple geographically diverse sites across the United States (prospective clinical isolates) and challenge/stock isolates (origin not specified but typically from strain collections). The study is prospective in terms of the clinical isolates.

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

• Not applicable. The ground truth for this type of device is established by a reference laboratory method (NCCLS reference broth microdilution method), not by expert consensus in the same way an image interpretation device might use radiologists.

4. Adjudication method for the test set:

• Not applicable. The reference method (NCCLS broth microdilution) provides the definitive result, not a human interpretation requiring adjudication.

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?

• No, this is not an MRMC study and does not involve human readers for interpretation in the same way an AI-powered diagnostic imaging device would. The device provides automated results (MIC values and categorical interpretations), and its performance is compared directly to a reference method, not to human readers.

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

• Yes, this is a standalone performance study. The BD Phoenix System's (algorithm only, as it's an automated system) results are directly compared to the NCCLS reference broth microdilution method without human intervention in the interpretation of the Phoenix results for the purpose of the comparison.

7. The type of ground truth used:

• Reference Method: NCCLS reference broth microdilution method (AST panels prepared according to NCCLS M7). This is a well-established, standardized laboratory method considered the "gold standard" for antimicrobial susceptibility testing.
• Expected Results: For challenge set isolates, the Phoenix System results were compared to "expected results," which would be previously determined and validated values for those specific strains.

8. The sample size for the training set:

• Not specified. The document describes a "test set" and emphasizes the comparison to a reference method, but it does not detail the size or composition of any specific training set used for the development of the Phoenix System's algorithms. As this device was cleared in 2002, the development methodologies might predate explicit "training set" and "test set" distinctions as commonly described in modern AI/ML development.

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

• Not specified as there is no explicit mention of a training set in the provided summary. However, implicitly, the development of the Phoenix System's algorithms would have involved extensive testing against known reference methods to establish the parameters for accurate MIC determination and categorical interpretation.

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