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Intended Use:
The Selux AST System is intended to be used for the automated quantitative susceptibility testing for most clinically significant aerobic microorganisms. The Selux AST System does not provide organism identification.

Indications for Use:
The Selux Gram-Negative Panel is intended for use with the Selux AST System as an in vitro test to determine the susceptibility of isolated colonies of specific gram-negative bacilli to specific antimicrobial agents when used as instructed.

The Selux Gram-Negative Panel is a quantitative test for the following antimicrobial agents with the specific organisms identified below:

• Amikacin: Pseudomonas aeruginosa
• Amoxicillin-Clavulanate: Escherichia coli, Klebsiella species (including K. oxytoca, K. pneumoniae), Proteus mirabilis
• Ampicillin: Escherichia coli, Proteus mirabilis
• Ampicillin-Sulbactam: Acinetobacter baumannii complex, Escherichia species (including K. oxytoca, K. pneumoniae), Proteus mirabilis, Proteus vulgaris
• Aztreonam: Escherichia coli
• Cefazolin: Escherichia coli, Klebsiella pneumoniae
• Cefepime: Citrobacter freundii complex, Citrobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae, Morganii, Proteus mirabilis, Proteus vulgaris, Serratia marcescens
• Cefoxitin: Escherichia coli, Klebsiella species (including K. oxytoca, K. pneumoniae), Morganii
• Ceftazidime: Citrobacter species (including C. freundii complex, C. koseri), Enterobacter cloacae complex, Escherichia coli, Klebsiella species (including K. aerogenes, K. pneumoniae), Proteus mirabilis, Proteus vulgaris, Serratia marcescens
• Ceftazidime-Avibactam: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella pneumoniae, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Pseudomonas aeruginosa, Serratia marcescens
• Ceftriaxone: Citrobacter freundii complex, Citrobacter koseri, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae, Proteus mirabilis
• Ciprofloxacin: Citrobacter freundii complex, Citrobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae, Morganii, Proteus mirabilis, Proteus vulgaris, Pseudomonas aeruginosa
• Eravacycline: Citrobacter freundii complex, Enterobacter cloacae complex, Escherichia oxytoca
• Ertapenem: Citrobacter freundii complex, Citrobacter koseri, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Serratia marcescens
• Gentamicin: Citrobacter species (including C. freundii complex, C. koseri), Enterobacter cloacae complex, Escherichia coli, Klebsiella species (including K. aerogenes, K. oxytoca, K. pneumoniae), Proteus species (including P. mirabilis, P. vulgaris), Pseudomonas aeruginosa, Serratia marcescens
• Imipenem-Relebactam: Citrobacter freundii complex, Citrobacter koseri, Escherichia coli, Klebsiella oxytoca, Pseudomonas aeruginosa
• Levofloxacin: Citrobacter freundii complex, Citrobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae, Morganii, Proteus mirabilis, Proteus vulgaris, Serratia marcescens
• Meropenem: Citrohacter freundii complex. Citrobacter cloacae complex. Escherichia coli. Klebsiella oxvtoca, Klebsiella pneumoniae, Morganella morganii. Proteus mirabilis, Proteus vulgaris, Pseudomonas aeruginosa, Serratia marcescens
• Meropenem-Vaborbactam: Citrobacter freundii complex, Citrobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella pneumoniae, Morganella morganii, Serratia marcescens
• Minocycline: Escherichia coli, Klebsiella species (including K. aerogenes, K. oxytoca, K. pneumoniae)
• Piperacillin-Tazobactam: Citrobacter koseri, Escherichia coli, Klebsiella pneumoniae, Morganii, Proteus mirabilis, Proteus vulgaris
• Tobramycin: Pseudomonas aeruginosa
• Trimethoprim-Sulfamethoxazole: Enterobacter cloacae complex, Klebsiella species (including K. aerogenes, K. oxytoca, K. pneumoniae)

The Selux AST System for antimicrobial susceptibility testing (AST) consists of a Sample Prep Station, an Inoculator, an Analyzer, a computer workstation, and the reagents and consumables required to perform AST testing. The system is operated via software that guides users through the manual sample preparation process and operates the automated Inoculator and Analyzer. The software includes an algorithm that enables the system to determine the susceptibilities of an organism to the variety of antimicrobials under test.

The system is designed so that only Gram stain information is required to initiate testing (to select the proper antimicrobial panel, gram-negative or gram-positive). While complete system testing can be performed without species-level identification (ID), this information is required for the system to report susceptibility results. Species ID can be performed by any appropriate method and this information can be either manually input to the Selux system or automatically downloaded from the laboratory information system (LIS) at any time, once the sample ID is entered into the system.

The system utilizes 384-well panels to provide parallel results for a large number of antimicrobials. Its average time-to-result is under 6 hours, as demonstrated in various studies.

Principle of Operation
The Selux platform performs AST similarly to the reference broth microdilution method by first incubating samples, then quantifying microbial growth in each well of an antimicrobial dilution series after a growth period, and finally determining the MIC by comparing growth data in each well. The Selux AST test requires that the Gram type (Classification) of the organism be known prior to testing as the information is necessary to select the proper AST panel to use. The organism identification (ID) need not be known for Selux AST processing to be performed. However, the organism ID is necessary for a result to be obtained because the MIC-determining algorithm is species-specific as is the interpretative Susceptible, Intermediate, or Resistant (SIR) determination. Any FDA-cleared method may be used to provide an ID including biochemical techniques, matrixassisted laser desorption/isotherm mass spectrometry, and multiplex genetic assays.

To ensure accurate results, the Selux method initiates antimicrobial susceptibility assays only after sufficient microorganism replication has occurred. Following determination of sufficient growth, two complementary metabolic assays are performed that quantify microbial growth, namely an indicator assay to estimate the number of bacteria present and a surface binding assay. These data are input to an MIC-determining algorithm that provides results when organism IDs are available. The sufficient growth assay ensures that the metabolic reagents used for the high-sensitivity organism quantification assays are not added until after sufficient microbial growth has occurred. To get an accurate reading of microbial replication, the sufficient growth assay monitors growth in dedicated AST panel wells that contain organisms and cation-adjusted Mueller-Hinton Broth but no antimicrobials or probes. Sufficient growth assay wells are monitored by fluorescence to those wells which the standard viability assay pair resazurin/methylene blue have been added and/or by optical absorbance.

Two probe-based assays, a viability assay and a surface area assay, commence across all wells in the panel after the sufficient growth threshold has been met. Both of these assays are performed in each AST panel well, providing two complementary datasets for each well.

Here's a summary of the acceptance criteria and study details for the Selux AST System, based on the provided FDA 510(k) summary:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for the Selux AST System are based on the comparison of its results with triplicate broth microdilution results from an independent reference laboratory. The specific performance metrics are "Essential Agreement" (EA) and "Category Agreement" (CA), along with an analysis of Very Major Errors (VMJ), Major Errors (MAJ), and Minor Errors (MIN). While the exact numerical acceptance criteria are not explicitly stated as "X% EA and Y% CA," the table below presents the reported performance, which implicitly met the FDA's requirements for substantial equivalence. The document states that the "Selux AST System meets performance criteria for each indication."

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size:
  • A total of 1401 clinical isolates (426 contemporary and 975 stock) and 222 challenge isolates were used.
  • This totals 1623 isolates across 12 Enterobacterales species, Acinetobacter baumannii complex, and Pseudomonas aeruginosa.
  • The number of data points for various antimicrobial-organism combinations ranged from 165 to 977, depending on the specific combination.
• Data Provenance: Clinical isolates were from "diverse geographic locations across the US." The study included both contemporary and frozen clinical isolates, as well as banked challenge isolates (selected for resistance profiles). This indicates a prospective and retrospective collection for clinical isolates and potentially retrospective for banked challenge isolates.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts

The document does not specify the number or qualifications of experts. However, it states that the ground truth was established by "triplicate broth microdilution results performed at an independent reference laboratory." This implies that the standard reference method for antimicrobial susceptibility testing was used, which is typically conducted by trained microbiologists.

4. Adjudication Method for the Test Set

The document does not explicitly describe an adjudication method for discrepancies between the device and the reference method. The comparison methodology is directly stated as: "Selux AST System performance was determined by comparing Selux AST System results with triplicate broth microdilution results performed at an independent reference laboratory." This suggests a direct comparison rather than an adjudication process by additional experts for discordant results.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No, an MRMC comparative effectiveness study involving human readers with and without AI assistance was not done. This device is an automated antimicrobial susceptibility testing system, not an imaging or diagnostic device that typically involves human interpretation of outputs aided by AI. Its performance is compared directly to a reference laboratory method for accuracy.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

Yes, the study described is a standalone performance evaluation of the Selux AST System. The system "determines the susceptibilities of an organism to the variety of antimicrobials under test" using its integrated software and algorithm. While human input is required for initial sample preparation and entry of organism identification (which can be manual or LIS-automated), the core susceptibility determination by the system is automated ("algorithm only"). The results are then compared to the reference method (broth microdilution).

7. The Type of Ground Truth Used

The ground truth used was broth microdilution results, specifically "triplicate broth microdilution results performed at an independent reference laboratory." Broth microdilution is considered a gold standard reference method for antimicrobial susceptibility testing.

8. The Sample Size for the Training Set

The document does not explicitly state the sample size for the training set. The provided details focus on the validation/test set used for clinical performance evaluation.

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

Since the training set size and details are not provided, information on how its ground truth was established is also not available in this document.

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Intended Use:
The Selux AST System is intended to be used for the automated quantitative susceptibility testing for most clinically significant aerobic microorganisms. The Selux AST System does not provide organism identification.

Indications for Use:
The Selux Gram-Positive Panel is intended for use with the Selux AST System as an in vitro test to determine the susceptibility of isolated colonies of specific Staphylococcus species to species to specific antimicrobial agents when used as instructed.

The Selux Gram-Positive Panel is a quantitative test for the following antimicrobial agents with the specific organisms identified below:

• Ampicillin: Enterococcus faecium, Enterococcus faecalis
• Clindamycin: Staphylococcus aureus, Staphylococcus epidermidis
• Ceftaroline: Staphylococcus aureus
• Daptomycin: Staphylococcus aureus, Enterococcus faecalis
• Delafloxacin: Staphylococcus aureus, Staphylococcus haemolyticus, Enterococcus faecalis
• Eravacycline: Staphylococcus aureus, Enterococcus faecalis
• Erythromycin: Staphylococcus aureus
• Linezolid: Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Enterococcus faecium, Enterococcus faecalis
• Levofloxacin: Enterococcus faccium, Enterococcus faecalis, methicillin-susceptible Staphylococcus aureus
• Minocycline: Staphylococcus aureus
• Oxacillin: Staphylococcus aureus, Staphylococcus lugdunensis
• Penicillin: Enterococcus faecium, Enterococcus faecalis, Staphylococcus aureus
• Trimethoprim: Staphylococcus aureus, Coagulase-Negative Staphylococci (including S. capitus, S. haemolyticus, S. saprophyticus, S. simulans)
• Vancomycin: Staphylococcus aureus, Coagulase-Negative Staphylococci (CoNS) (including S. capitus, S. cohnii, S. epidermidis, S. haemolyticus, S. internedius group, S. lugdunensis, S. saprophyticus, S. schleiferi, S. simulans) Enterococcus faecium, Enterococcus faecalis

The Selux Gram-Positive Panel is a qualitative test for the following antimicrobial agents with the specific target organisms identified below:

• Cefoxitin Screen to predict mecA-mediated oxacillin resistance: Staphylococcus aureus, Staphylococcus lugdunensis

The Selux AST System for antimicrobial susceptibility testing (AST) consists of a Sample Prep Station, an Inoculator, an Analyzer, a computer workstation, and the reagents and consumables required to perform AST testing. The system is operated via software that guides users through the manual sample preparation process and operates the automated Inoculator and Analyzer. The software includes an algorithm that enables the system to determine the susceptibilities of an organism to the variety of antimicrobials under test.

The system is designed so that only Gram stain information is required to initiate testing (to select the proper antimicrobial panel, gram-negative or gram-positive). While complete system testing can be performed without species-level identification (ID), this information is required for the system to report susceptibility results. Species ID can be performed by any appropriate method and this information can be either manually input to the Selux system or automatically downloaded from the laboratory information system (LIS) at any time, once the sample ID is entered into the LIS.

The system utilizes 384-well panels to provide parallel results for a large number of antimicrobials. Its average time-to-result is under 6 hours, as demonstrated in various studies.

Here's a breakdown of the acceptance criteria and study information for the Selux AST System, based on the provided FDA 510(k) summary:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for each antimicrobial-organism combination are not explicitly stated as numerical targets (e.g., "EA must be >90%"). Instead, the document presents the observed performance and notes where EA (Essential Agreement) falls below 90%, implying that 90% is a general benchmark for acceptable performance, with specific justifications or labeling changes for values below this. The table below summarizes the reported performance.

¹ EA performance (<90%) is addressed in limitation statements in the device labeling.

2. Sample Size Used for the Test Set and Data Provenance

• Test Set Sample Size:
  • Clinical Isolates: 706 (193 contemporary and 513 stock/frozen)
  • Challenge Isolates: 159
  • Total Samples Tested: 865
  • The number of data points for various antimicrobial-organism combinations ranged from 39 to 311.
• Data Provenance: The document states "Contemporary and frozen clinical isolates from diverse geographic locations across the US were evaluated for performance as well as stock (frozen/banked) challenge isolates." This indicates a mix of retrospective (stock/frozen) and potentially prospective (contemporary) data collected from multiple sites across the US.

3. Number of Experts Used to Establish Ground Truth for the Test Set and Their Qualifications

The document does not explicitly state the number of experts or their specific qualifications for establishing the ground truth. It mentions that the Selux AST System results were compared with "triplicate broth microdilution results performed at an independent reference laboratory."

4. Adjudication Method for the Test Set

The ground truth was established by "triplicate broth microdilution results performed at an independent reference laboratory." This implies that the accepted standard for antimicrobial susceptibility testing (broth microdilution) was performed independently, and the "triplicate" nature suggests internal verification or averaging, rather than a formal adjudication process involving multiple human readers for discrepancies.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, and Effect Size

No, an MRMC comparative effectiveness study involving human readers with and without AI assistance was not conducted. The study evaluated the standalone performance of the Selux AST System against a reference method (broth microdilution), which is a device-to-device comparison, not a human reader study.

6. If a Standalone Study Was Done

Yes, a standalone study was done. The entire "Clinical Studies" section describes the performance of the Selux AST System (the algorithm/device only) in determining antimicrobial susceptibility, comparing its results directly to a reference method (broth microdilution). Human involvement was in operating the system and performing the reference method, not in interpreting the results from the Selux system.

7. The Type of Ground Truth Used

The ground truth used was reference standard testing, specifically triplicate broth microdilution results performed at an independent reference laboratory.

8. The Sample Size for the Training Set

The document does not explicitly state the sample size for the training set. The "Clinical Studies" section describes the test set used for performance evaluation.

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

Since the training set size and details are not provided, information on how its ground truth was established is also not available in the document.

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