(56 days)
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 antimicrobial agent linezolid at concentrations of 0.25 - 32 ug/mL to Gram Positive ID/AST or AST only Phoenix panels. Linezolid 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:
Enterococcus faecium (vancomycin resistant strains)
Staphylococcus aureus (including methicillin resistant strains)
Active In Vitro Against:
Enterococcus faecalis (including vancomycin resistant strains)
Enterococcus faecium (vancomycin susceptible strains)
Staphylococcus epidermidis (including methicillin resistant strains)
Staphylococcus haemolvticus
The BD Phocnix 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 Phocnix instrument and software.
- BD Phocnix 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 3.5℃. The instrument takes readings of the panels every 20 minutes. The readings are merpreted 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).
The performed study is a standalone study, implying that the algorithm’s performance was evaluated independently without human intervention.
The ground truth for the study was established using a reference method, specifically the NCCLS reference broth microdilution method (AST panels prepared according to NCCLS M7).
The data provenance for the clinical studies includes clinical, stock, and challenge isolates tested across multiple geographically diverse sites across the United States. While the exact numerical sample size for the clinical isolates is not provided, the challenge set isolates were compared to expected results, and clinical isolates were compared to the NCCLS reference method.
The sample size for the training set is not explicitly mentioned in the provided text.
Adjudication Method: The text does not explicitly describe an adjudication method for the test set.
Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study: The document does not mention a multi-reader multi-case (MRMC) comparative effectiveness study, nor does it provide an effect size for human readers improving with AI vs. without AI assistance.
Here is a table summarizing the acceptance criteria and the reported device performance:
Acceptance Criteria and Device Performance
| Metric | Acceptance Criteria (Implicit from FDA Guidance) | Reported Device Performance |
|---|---|---|
| Overall Intra-site Reproducibility (Linezolid) | >90% | >90% |
| Overall Inter-site Reproducibility (Linezolid) | >95% | >95% |
| Clinical Performance (Linezolid) | ||
| Essential Agreement (EA) for Gram-Positive Organisms | Not explicitly stated but expected to be high for regulatory approval (typically >90%) | Not explicitly enumerated with a specific percentage for Linezolid in the provided table. The table is malformed. |
| Category Agreement (CA) for Gram-Positive Organisms | Not explicitly stated but expected to be high for regulatory approval (typically >90%) | Not explicitly enumerated with a specific percentage for Linezolid in the provided table. The table is malformed. |
Study Details
| Feature | Description |
|---|---|
| Sample Sizes | Test Set (Clinical Studies): The exact number of clinical isolates is not specified. However, the study included clinical, stock, and challenge isolates. For reproducibility, a panel of Gram-positive isolates was tested in triplicate on three different days using one lot of panels. |
| Training Set: Not explicitly stated in the provided text. | |
| Data Provenance | Clinical, stock, and challenge isolates were tested across multiple geographically diverse sites across the United States. The text does not explicitly state whether the data was retrospective or prospective, but the description of "clinical studies" and "challenge isolates" suggests a prospective or a mix of prospective and curated retrospective data. |
| Number of Experts / Qualifications for Ground Truth - Test Set | Not applicable; the ground truth was established by a reference laboratory method rather than human experts. |
| Adjudication Method - Test Set | Not applicable. The ground truth was established by the NCCLS reference broth microdilution method, not by expert consensus requiring adjudication. |
| MRMC Comparative Effectiveness Study | Not performed. The study evaluates the standalone performance of the BD Phoenix System against a reference method. |
| Standalone Performance | Yes, a standalone (algorithm only) performance study was conducted. The BD Phoenix™ Automated Microbiology System's performance was compared directly to the NCCLS reference broth microdilution method. |
| Type of Ground Truth | Reference method ground truth: The NCCLS reference broth microdilution method (AST panels prepared according to NCCLS M7) was used as the ground truth for clinical isolates. For challenge set isolates, their performance was compared to "expected results," which would also be based on established reference methods or expert consensus on known strains. |
| How Ground Truth for Training Set was Established | Not explicitly stated due to the absence of specific details on the training set. However, it is highly probable that if a training set were used, its ground truth would be established similarly to the test set, using a gold standard reference method for antimicrobial susceptibility testing. |
§ 866.1645 Fully automated short-term incubation cycle antimicrobial susceptibility system.
(a)
Identification. A fully automated short-term incubation cycle antimicrobial susceptibility system is a device that incorporates concentrations of antimicrobial agents into a system for the purpose of determining in vitro susceptibility of bacterial pathogens isolated from clinical specimens. Test results obtained from short-term (less than 16 hours) incubation are used to determine the antimicrobial agent of choice to treat bacterial diseases.(b)
Classification. Class II (special controls). The special control for this device is FDA's guidance document entitled “Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA.”