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The BD Phoenix™ Automated Microbiology System is intended for the in vitro rapid identification (ID) and quantitative determination of antimicrobial susceptibility by minimal inhibitory concentration (MIC) of Gram Negative aerobic and facultative anaerobic bacteria belonging to the family Enterobacteriaceae and non-Enterobacteriaceae.

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. Enterococcus and Streptococcus.

This premarket notification is for the antimicrobial agent meropenem at concentrations of 0.125-32 us/mL to Gram-negative ID/AST or AST only Phoenix panels. Meropenem has been shown to be active in vitro against most strains of microorganisms listed below, as described in the FDAapproved package inserts for this antimicrobial agent.

Active In Vitro and in Clinical Infections Against:
Escherichia coli
Klebsiella pneumoniae
Pseudomonas aeruginosa

Active In Vitro
Citrobacter koseri (formerly diversus)
Citrobacter freundii
Enterobacter cloacae
Klebsiella oxytoca
Morganella morganii
Proteus vulgaris
Serratia marcescens

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 o 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. Inoculum for use with the Phoenix system may be prepared either manually or may be automated using the BD Phoenix™ AP System.

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° ± 1°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, R or N (susceptible, intermediate, resistant or not susceptible).

Here's a breakdown of the acceptance criteria and study details for the K132674 submission, based on the provided text:

Acceptance Criteria and Device Performance

Note: The document states that the system "demonstrated substantially equivalent performance when compared to the CLSI reference broth microdilution method" and "the data collected from the substantial equivalence studies demonstrate that testing on the BD Phoenix™ Automated Microbiology System with this antimicrobial agent is substantially equivalent as outlined in the FDA draft guidance document, 'Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA', August 28, 2009." This implies that the acceptance criteria are based on meeting the performance thresholds outlined in that FDA guidance, which typically requires high percentages for EA and CA.

Study Details

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

   • Test Set Sample Size: 1202 isolates (combined Clinical and Challenge isolates for Meropenem, as indicated by 'n=1202' for EA and CA).
   • Data Provenance: The study used "Clinical, stock and challenge isolates across multiple geographically diverse sites across the United States." This indicates a prospective and/or retrospective collection of isolates from clinical settings and possibly curated stock/challenge collections within the US.

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

   • The document does not specify the number or qualifications of experts used to establish ground truth.
   • Ground truth for clinical isolates was "compared to the results obtained from the CLSI reference broth microdilution method." The CLSI method itself is a standardized laboratory procedure, not typically an expert consensus per se, though it is executed by trained laboratory personnel.
   • Ground truth for challenge isolates was compared to "expected results," which would be internally validated results for those specific strains.

3. Adjudication method for the test set:

   • The document does not explicitly state an adjudication method (like 2+1, 3+1). The comparison is directly between the BD Phoenix results and the CLSI reference method or "expected results" for challenge strains. This suggests a direct comparison rather than a multi-expert adjudication process for each case.

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, a multi-reader multi-case (MRMC) comparative effectiveness study was not explicitly mentioned or performed. This device is an automated system for antimicrobial susceptibility testing, which essentially replaces manual interpretation of susceptibility, rather than assisting human readers in an interpretive task like image analysis. The "comparison" is to an established reference method (CLSI broth microdilution), not to human readers.

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

   • Yes, this was a standalone performance evaluation. The BD Phoenix System is an automated device designed to produce MIC values and categorical interpretations (S, I, R) without human intervention in the interpretation process once the panel is loaded. The "Phoenix System results" were directly compared to the reference method.

6. The type of ground truth used:

   • For clinical isolates: The ground truth was established by the CLSI reference broth microdilution method. This is a laboratory-based, standardized, quantitative method considered the gold standard for antimicrobial susceptibility testing.
   • For challenge isolates: The ground truth was "expected results," implying predefined, validated results for these specific strains.

7. The sample size for the training set:

   • The document does not specify the sample size for any training set. It focuses on the performance evaluation against the reference method using clinical and challenge isolates. For an AST system, the "training" (if it even applies in the traditional sense) would likely refer to the development and optimization of the algorithms within the system using various bacterial strains and antimicrobial combinations, but this information is not provided for this specific submission.

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

   • This information is not provided in the document as no specific "training set" and its ground truth establishment are detailed.

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