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

Device Description

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.

AI/ML Overview

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.

Antimicrobial	Organism Group	Total Tested	# in EA (Essential Agreement)	% EA	# in CA (Category Agreement)	% CA	# R (Resistant)	# VMJ (Very Major Errors)	# MAJ (Major Errors)	# MIN (Minor Errors)
Ampicillin	Enterococcus spp.	299	294	98.3	299	100	163	0	0	0
Clindamycin	Staphylococcus spp.	311	298	95.8	302	97.1	73	1	3	5
Ceftaroline	Staphylococcus spp.	138	136	98.6	136	98.6	1	0	1	1
Daptomycin	Enterococcus spp.	116	109	94	116	100	0	0	0	0
	Staphylococcus spp.	134	132	98.5	133	99.3	1	1	0	0
Delafloxacin	Enterococcus spp.	180	175	97.2	164	91.1	38	0	2	14
	Staphylococcus spp.	229	227	99.1	216	94.3	14	0	0	13
Eravacycline	Enterococcus spp.¹	287	248	86.4	280	97.6	6	2	5	0
	Staphylococcus spp.	118	118	100	118	100	2	0	0	0
Erythromycin	Staphylococcus spp.	220	204	92.7	208	94.5	123	0	5	7
Linezolid	Enterococcus spp.	299	287	96	294	98.3	1	0	3	2
	Staphylococcus spp.	228	223	97.8	227	99.6	3	0	1	0
Levofloxacin	Enterococcus spp.	281	272	96.8	272	96.8	129	2	2	5
	Staphylococcus spp.	135	132	97.8	130	96.3	43	0	1	4
Minocycline	Staphylococcus spp.	217	210	96.8	214	98.6	2	1	0	2
Oxacillin	Staphylococcus aureus¹	122	104	85.2	121	99.2	49	1	0	0
	Staphylococcus lugdunensis¹	39	35	89.7	37	94.9	3	0	2	0
Penicillin	Enterococcus spp.	238	223	93.7	234	98.3	105	0	4	0
	Staphylococcus spp.¹	204	172	84.3	200	98	163	4	0	0
Trimethoprim	Staphylococcus spp.	215	196	91.2	211	98.1	33	2	2	0
Vancomycin	Enterococcus spp.	199	187	94	195	98	64	0	2	2
	Staphylococcus aureus	238	236	99.2	236	99.2	0	0	1	1
	Coagulase-negative Staphylococci	111	109	98.2	111	100	0	0	0	0
Cefoxitin Screen	Staphylococcus aureus, Staphylococcus lugdunensis	175	172	98.3	N/A	N/A	81	1	2	N/A

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.

Summary

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Image /page/0/Picture/0 description: The image contains the logo of the U.S. Food and Drug Administration (FDA). On the left is the Department of Health & Human Services logo. To the right of that is the FDA logo, which is a blue square with the letters "FDA" in white. To the right of the blue square is the text "U.S. FOOD & DRUG ADMINISTRATION" in blue.

January 18, 2023

Selux Diagnostics, Inc. % Patricia Shrader Regulatory Consultant PBO Consulting 2212 East Pratt Street Baltimore, Maryland 21231

Re: K211759

Trade/Device Name: Selux AST System; Model AST Gen 1.0 Regulation Number: 21 CFR 866.1645 Regulation Name: Fully Automated Short-Term Incubation Cycle Antimicrobial Susceptibility System Regulatory Class: Class II Product Code: LON, LTT, LTW Dated: June 4, 2021 Received: June 7, 2021

Dear Patricia Shrader:

We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. Although this letter refers to your product as a device, please be aware that some cleared products may instead be combination products. The 510(k) Premarket Notification Database located at https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm identifies combination product submissions. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.

If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.

Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's

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requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801 and Part 809); medical device reporting of medical device-related adverse events) (21 CFR 803) for devices or postmarketing safety reporting (21 CFR 4, Subpart B) for combination products (see https://www.fda.gov/combination-products/guidance-regulatory-information/postmarketing-safety-reportingcombination-products); good manufacturing practice requirements as set forth in the quality systems (OS) regulation (21 CFR Part 820) for devices or current good manufacturing practices (21 CFR 4, Subpart A) for combination products; and, if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.

Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to https://www.fda.gov/medical-device-safety/medical-device-reportingmdr-how-report-medical-device-problems.

For comprehensive regulatory information about mediation-emitting products, including information about labeling regulations, please see Device Advice (https://www.fda.gov/medicaldevices/device-advice-comprehensive-regulatory-assistance) and CDRH Learn (https://www.fda.gov/training-and-continuing-education/cdrh-learn). Additionally, you may contact the Division of Industry and Consumer Education (DICE) to ask a question about a specific regulatory topic. See the DICE website (https://www.fda.gov/medical-device-advice-comprehensive-regulatoryassistance/contact-us-division-industry-and-consumer-education-dice) for more information or contact DICE by email (DICE@fda.hhs.gov) or phone (1-800-638-2041 or 301-796-7100).

Sincerely,

Ribhi Shawar -S

Ribhi Shawar, Ph.D. (ABMM) Branch Chief, General Bacteriology and Antimicrobial Susceptibility Branch Division of Microbiology Devices OHT7: Office of In Vitro Diagnostics Office of Product Evaluation and Quality Center for Devices and Radiological Health

Enclosure

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Indications for Use

510(k) Number (if known) K211759

Device Name Selux AST System

Indications for Use (Describe)

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
Type of Use (Select one or both, as applicable)

X Prescription Use (Part 21 CFR 801 Subpart D)

Over-The-Counter Use (21 CFR 801 Subpart C)

CONTINUE ON A SEPARATE PAGE IF NEEDED.

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510(k) Summary for the Selux AST System, Antimicrobial Susceptibility Test System

Date prepared: December 10, 2022

Submitter:

Selux Diagnostics, Inc. 56 Roland St Suite 106 Charlestown, MA 02129 Tel. 617-945-9383

Contact:

Eric Stern, Ph.D. Tel. 617-945-9383

Subject Device

Trade Name:	Selux AST System
Common Name:	Antimicrobial Susceptibility Test System
Regulation Number:	21 CFR 866.1645
Regulation Name:	Fully automated short-term incubation cycle antimicrobial susceptibility system
Regulatory Class:	Class II
Product Code:	LON, LTT, LTW
Classification Panel:	83 (Microbiology)

Primary Predicate Device(s)

Trade Name:	BD Phoenix Automated Microbiology System- Vancomycin 0.5-32 µg/mL
Manufacturer:	Becton, Dickinson and Company
510(k) Reference:	K131331
Common Name:	Antimicrobial Susceptibility Test System
Regulation Number:	21 CFR 866.1645
Regulation Name:	Fully automated short-term incubation cycle antimicrobial susceptibility system
Regulatory Class:	Class II
Product Code:	LON
Classification Panel:	83 (Microbiology)

Device Description

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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 bv 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.

Intended Use and Indications for Use

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

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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 and Enterococcus 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 O
Clindamycin: Staphylococcus aureus, Staphylococcus epidermidis O
Ceftaroline: Staphylococcus aureus o
Daptomycin: Staphylococcus aureus, Enterococcus faecalis O
Delafloxacin: Staphylococcus aureus, Staphylococcus haemolyticus, Enterococcus o faecalis
Eravacycline: Staphylococcus aureus, Enterococcus faecalis O
Erythromycin: Staphylococcus aureus O
Linezolid: Staphylococcus aureus, Staphylococcus epidermidis, Staphvlococcus o haemolyticus, Enterococcus faecium, Enterococcus faecalis
Levofloxacin: Enterococcus faecium, Enterococcus faecalis, methicillin-susceptible o Staphylococcus aureus
Minocycline: Staphylococcus aureus O
Oxacillin: Staphylococcus aureus, Staphylococcus lugdunensis O
Penicillin: Enterococcus faecium. Enterococcus faecalis. Staphylococcus aureus o
Trimethoprim: Staphylococcus aureus, Coagulase-Negative Staphylococci (CoNS) O (including S. capitis, S. haemolyticus, S. saprophyticus, S. simulans)
Vancomycin: Staphylococcus aureus, Coagulase-Negative Staphylococci (CoNS) O (including S. capitis, S. cohnii. S. epidermidis, S. hamolyticus, S. intermedius 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, o Staphylococcus lugdunensis

Comparison of Technological Characteristics with the Predicate Device

The technological characteristics of the Selux AST System are substantially equivalent to the predicate, the BD Phoenix Automated Microbiology System- Vancomycin 0.5-32 ug/mL (K131331) in terms of intended use, application, user population, basic design, performance, and labeling.

Specification	Selux AST System	K131331
Device Trade Name	Selux AST System	BD Phoenix AutomatedMicrobiology System-Vancomycin 0.5-32 µg/mL
Specification	Selux AST System	K131331
Indication for Use	The Selux AST System is intended to be used for the automated quantitative or qualitative susceptibility testing for most clinically significant aerobic microorganisms. The Selux AST System does not provide organism identification.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 and Enterococcus species to specific antimicrobial agents when used as instructed.	The BD Phoenix Automated Microbiology System is intended for the in vitro rapid identification (ID) of gram positive bacteria from pure culture belonging to the genera Staphylococcus , Enterococcus , other gram positive cocci and gram positive bacilli. The BD Phoenix Automated Microbiology System is also intended for the quantitative determination of antimicrobial susceptibility by minimal inhibitory concentration (MIC) of most gram positive bacteria isolates from pure culture belonging to the genera Staphylococcus and Enterococcus .
Sources of Microorganisms	Bacterial colonies isolated from culture	Same
Technology	Automated growth-based detection	Same
Methodology	Determinations of MIC using serial two-fold dilution format	Same
Read Method	Automated	Same
Inoculation Method	Automated	Same
Result Reported	Report results as minimum inhibitory concentration (MIC) and categorical interpretation (S, I, R, NS)	Report results as minimum inhibitory concentration (MIC) and categorical interpretation (S, I, R)
General Device Characteristic Differences
Antimicrobial Agent andReporting Range	Ampicillin - ≤0.25 to ≥128 µg/mLClindamycin - ≤0.03 to ≥16 µg/mLCeftaroline - ≤0.06 to ≥32 µg/mLDaptomycin - ≤0.06 to ≥32 µg/mLDelafloxacin - ≤0.008 to ≥8 µg/mLEravacycline - ≤0.002 to ≥0.5 µg/mLErythromycin - ≤0.06 to ≥32 µg/mLLevofloxacin - ≤0.06 to ≥32 µg/mLLinezolid - ≤0.25 to ≥32 µg/mLMinocycline - ≤0.12 to ≥64 µg/mLOxacillin - ≤0.03 to ≥32 µg/mLPenicillin - ≤0.03 to ≥64 µg/mLTrimethoprim – ≤0.25 to ≥64 µg/mLVancomycin - ≤0.12 to ≥128 µg/mL	Vancomycin ≤0.5 to ≥64 µg/mL
IVD Functions	AST	ID and AST
Instrument	Selux AST System	BD Phoenix Automated Microbiology System

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Despite the differences between the Selux AST System and the predicate, the overall risk and safety of system use is not affected.

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Reproducibility

Intra-site reproducibility was evaluated at a single site that participated in the inter-site reproducibility testing and the clinical study. A minimum of 5 isolates for each antimicrobial were tested in triplicate from three separate inoculums on three separate days for a total of 45 results per antimicrobial. Best-case intra-site reproducibility was ≥95% and worst-case intra-site reproducibility was ≥89% (see following table). Please note the best-case intra-site reproducibility for erythromycin is 93.6%, which is <95%; however, reproducibility testing at two other sites were 100%.

Selux AST System Intra-site Reproducibility
	All organisms (combined)		Indicated organisms only
Antimicrobial	Best-case (%)	Worst case (%)	Best-case (%)	Worst case (%)
Ampicillin	45/45 (100%)	45/45 (100%)	45/45 (100%)	45/45 (100%)
Cefoxitin screen	47/47 (100%)	47/47 (100%)	47/47 (100%)	47/47 (100%)
Ceftaroline	48/49 (98.0%)	48/49 (98.0%)	48/49 (98.0%)	48/49 (98.0%)
Clindamycin	54/54 (100%)	54/54 (100%)	36/36 (100%)	36/36 (100%)
Daptomycin	74/74 (100%)	74/74 (100%)	65/65 (100%)	65/65 (100%)
Eravacycline	103/103 (100%)	99/103 (96.1%)	103/103 (100%)	99/103 (96.1%)
Erythromycin	44/47 (93.6%)	42/47 (89.4%)	44/47 (93.6%)	42/47 (89.4%)
Linezolid	62/63 (98.4%)	62/63 (98.4%)	53/54 (98.1%)	53/54 (98.1%)
Oxacillin	62/65 (95.4%)	62/65 (95.4%)	62/65 (95.4%)	62/65 (95.4%)
Vancomycin	83/83 (100%)	79/83 (95.2%)	83/83 (100%)	79/83 (95.2%)

Inter-site reproducibility was evaluated by testing a minimum of 25 isolates for each of the 14 antimicrobials plus one screening test at each of three test sites that participated in the clinical study. Each isolate was tested once at each site for a total of three results per isolate (minimum 75 results per antimicrobial). Best-case inter-site reproducibility was ≥95% and worst-case inter-site reproducibility was ≥89% (see following table).

Selux AST System Inter-site Reproducibility
	All organisms (combined)		Indicated organisms only
Antimicrobial	Best-case (%)	Worst case (%)	Best-case (%)	Worst case (%)
Ampicillin	72/75 (96%)	72/75 (96%)	68/69 (98.6%)	68/69 (98.6%)
Cefoxitin screen	74/75 (98.7%)	74/75 (98.7%)	74/75 (98.7%)	74/75 (98.7%)
Ceftaroline	74/75 (98.7%)	74/75 (98.7%)	74/75 (98.7%)	74/75 (98.7%)
Clindamycin	78/81 (96.3%)	78/81 (96.3%)	63/66 (95.5%)	63/66 (95.5%)
Daptomycin	77/78 (98.7%)	77/78 (98.7%)	77/78 (98.6%)	77/78 (98.6%)
Delafloxacin	144/144 (100%)	144/144 (100%)	144/144 (100%)	144/144 (100%)
Eravacycline	78/78 (100%)	78/78 (100%)	78/78 (100%)	78/78 (100%)
Erythromycin	141/144 (97.9%)	136/144 (94.4%)	141/144 (97.9%)	136/144 (94.4%)
Levotloxacin	76/78 (97.4%)	76/78 (97.4%)	76/78 (97.4%)	76/78 (97.4%)
Linezolid	77/78 (98.7%)	77/78 (98.7%)	56/57 (98.2%)	56/57 (98.2%)
Minocycline	73/75 (97.3%)	73/75 (97.3%)	64/66 (97.0%)	64/66 (97.0%)
Oxacillin	76/78 (97.4%)	75/78 (96.2%)	76/78 (97.4%)	75/78 (96.2%)
Penicillin	74/78 (94.9%)	70/78 (89.7%)	74/78 (94.9%)	70/78 (89.7%)
Trimethoprim	77/81 (95.1%)	74/81 (91.4%)	77/81 (95.1%)	74/81 (91.4%)
Vancomycin	79/80 (98.8%)	75/80 (93.8%)	79/80 (98.8%)	75/80 (93.8%)

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Clinical Studies

The following table gives the antimicrobial-organism combinations tested and includes the
reporting range and breakpoints of each combination.

Antimicrobial	Abbreviation	Targeted Organism	Reporting Range	Breakpoints
Ampicillin	AMP	Enterococcus faeciumEnterococcus faecalis	≤0.25 to ≥128µg/mL	≤8 / ≥16
Clindamycin	CLI	Staphylococcus aureusStaphylococcusepidermidis	≤0.03 to ≥16µg/mL	≤0.5 / 1-2 / ≥4
Ceftaroline	CPT	Staphylococcus aureus	≤0.06 to ≥32µg/mL	≤1 / 2 / ≥4
Daptomycin	DAP	Enterococcus faecalisStaphylococcus aureus	≤0.06 to ≥32µg/mL	E. faecalis:≤2 / 4 / ≥8S. aureus: ≤1 (≥2 NS)
Delafloxacin	DFX	Enterococcus faecalisStaphylococcus aureusStaphylococcushaemolyticus	≤0.008 to ≥8µg/mL	Enterococcus spp.:≤0.12 / 0.25 / ≥0.5Staphylococcus spp.:≤0.25 / 0.5 / ≥1
Eravacycline	ERV	Enterococcus faecalisStaphylococcus aureus	≤0.002 to ≥0.5µg/mL	≤0.06 / ≥0.12
Erythromycin	ERY	Staphylococcus aureus	≤0.06 to ≥32µg/mL	≤0.5 / 1-4 / ≥8
Levofloxacin	LVX	Enterococcus faeciumEnterococcus faecalisMethicillin-susceptibleStaphylococcus aureus	≤0.06 to ≥32µg/mL	≤2 / 4 / ≥8
Linezolid	LNZ	Enterococcus faeciumEnterococcus faecalisStaphylococcus aureusStaphylococcusepidermidisStaphylococcushaemolyticus	≤0.25 to ≥32µg/mL	Enterococcus spp.:≤2 / 4 / ≥8Staphylococcus spp.:≤4 / ≥8
Minocycline	MIN	Staphylococcus aureus	≤0.12 to ≥64µg/mL	≤4 / 8 / ≥16
Oxacillin	OXA	Staphylococcus aureusStaphylococcuslugdunensis	≤0.03 to ≥32µg/mL	≤2 / ≥4
Penicillin	PEN	Enterococcus faeciumEnterococcus faecalisStaphylococcus aureus	≤0.03 to ≥64µg/mL	Enterococcus spp.:≤8 / ≥16S. aureus:≤0.12 / ≥0.25
Antimicrobial	Abbreviation	Targeted Organism	Reporting Range	Breakpoints
Trimethoprim	TMP	Staphylococcus aureusCoagulase-NegativeStaphylococci(CoNS) (including S.capitis, S.haemolyticus, S.saprophyticus, S.simulans)	≤0.25 to ≥64μg/mL	≤8 / ≥16
Vancomycin	VAN	Enterococcus faeciumEnterococcus faecalisStaphylococcus aureusCoagulase-NegativeStaphylococci(CoNS) (including S.capitis, S. cohnii, S.epidermidis, S.haemolyticus, S.hominis, S.intermedius group, S.lugdunensis, S.saprophyticus, S.schleiferi, S. simulans)	≤0.12 to ≥128μg/mL	Enterococcus spp.:≤4 / 8-16 / ≥32S. aureus:≤2 / 4-8 / ≥16CoNS:≤4 / 8-16 / ≥32
CefoxitinScreen topredict mecA-mediatedoxacillinresistance	FOX SCN	Staphylococcus aureusStaphylococcuslugdunensis	SN or SP	N/A

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Clinical performance testing on the Selux AST System was performed at three test sites. Contemporary and frozen clinical isolates from diverse geographic locations across the US were evaluated for performance as well as stock (frozen/banked) challenge isolates, which were selected for their rare resistance profiles. A total of 706 clinical (193 contemporary and 513 stock) and 159 challenge samples from 11 Staphylococci and 2 Enterococci species were tested to evaluate the Selux AST System performance for 14 antimicrobials and one screening test, the Cefoxitin Screen. Depending on the spectrum of activity, breakpoints and the claimed organisms (species/group) for each antimicrobial on the panel, the number of datapoints for the various antimicrobial-organisms tested varied and ranged from 39 (e.g. S. lugdunensis/Oxacillin) to 311 (e.g. Staphylococcus/Clindamycin).

Selux AST System performance was determined by comparing Selux AST System results with triplicate broth microdilution results performed at an independent reference laboratory. The Selux AST System meets performance criteria for each indication and is given in the following table summarized by reporting group. Additionally, QC testing was performed every day testing was performed at each site and met the 95% performance criteria for all antimicrobials.

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		Total
Antimicrobial	Organism Group	Tested	# in EA	% EA	# in CA	% CA	# R	# VMJ	# MAJ	# MIN
Ampicillin	Enterococcus spp.	299	294	98.3	299	100	163	0	0	0
Clindamycin	Staphylococcus spp.	311	298	95.8	302	97.1	73	1	3	5
Ceftaroline	Staphylococcus spp.	138	136	98.6	136	98.6	1	0	1	1
Daptomycin	Enterococcus spp.	116	109	94	116	100	0	0	0	0
	Staphylococcus spp.	134	132	98.5	133	99.3	1	1	0	0
Delafloxacin	Enterococcus spp.	180	175	97.2	164	91.1	38	0	2	14
	Staphylococcus spp.	229	227	99.1	216	94.3	14	0	0	13
Eravacycline	Enterococcus spp.¹	287	248	86.4	280	97.6	6	2	5	0
	Staphylococcus spp.	118	118	100	118	100	2	0	0	0
Erythromycin	Staphylococcus spp.	220	204	92.7	208	94.5	123	0	5	7
Linezolid	Enterococcus spp.	299	287	96	294	98.3	1	0	3	2
	Staphylococcus spp.	228	223	97.8	227	99.6	3	0	1	0
Levofloxacin	Enterococcus spp.	281	272	96.8	272	96.8	129	2	2	5
	Staphylococcus spp.	135	132	97.8	130	96.3	43	0	1	4
Minocycline	Staphylococcus spp.	217	210	96.8	214	98.6	2	1	0	2
Oxacillin	Staphylococcus aureus¹	122	104	85.2	121	99.2	49	1	0	0
	Staphylococcus lugdunensis¹	39	35	89.7	37	94.9	3	0	2	0
Penicillin	Enterococcus spp.	238	223	93.7	234	98.3	105	0	4	0
	Staphylococcus spp.¹	204	172	84.3	200	98	163	4	0	0
Trimethoprim	Staphylococcus spp.	215	196	91.2	211	98.1	33	2	2	0
Vancomycin	Enterococcus spp.	199	187	94	195	98	64	0	2	2
	Staphylcoccus aureus	238	236	99.2	236	99.2	0	0	1	1
	Coagulase-negativeStaphylococci	111	109	98.2	111	100	0	0	0	0

Screening Test	Organism Group	TotalTested	#Agree	%Agree	# R	# VMJ	# MAJ
Cefoxitin Screen	Staphylococcus aureus ,Staphylococcus lugdunensis	175	172	98.3	81	1	2

Conclusion

Based on our studies and testing, the Selux AST System was determined to be substantially equivalent to the predicate device (K131331).

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

Regulation Number and Section

§ 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.”