The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System is an in vitro diagnostic product for clinical susceptibility testing of non-fastidious isolates.

This 510(k) is for ciprofloxacin in the dilution range of 0.002-64 ug/mL for testing non-fastidious gram-negative isolates on The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System. Testing is indicated for Enterobacterales and Pseudomonas aeruginosa, as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC) webpage.

The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Ciprofloxacin in the dilution range of 0.002-64 ug/mL demonstrated acceptable performance with the following organisms:

Enterobacterales (C. freundii, C. koseri, E. cloacae complex, E. coli, K. aerogenes, K. oxytoca, K.pneumoniae, M. morganii, P. mirabilis, P. rettgeri, P. stuartii, P. vulgaris, S. marcescens)

Pseudomonas aeruginosa

Device Description

Not Found

AI/ML Overview

The provided FDA 510(k) clearance letter (K250990) for "The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Ciprofloxacin in the dilution range of 0.002-64 µg/mL" does not include detailed information about the acceptance criteria or the specific study that proves the device meets those criteria. The letter primarily serves as a notification of substantial equivalence and outlines regulatory requirements.

However, based on the nature of the device (Antimicrobial Susceptibility Test) and the context of FDA clearance for such products, we can infer the typical types of acceptance criteria and studies that would have been conducted. Please note that the specific numerical values for acceptance criteria and study details are not present in the provided document and would normally be found in the manufacturer's 510(k) submission summary.

Here's a breakdown of the requested information, with inferred details for sections not explicitly stated:

Acceptance Criteria and Device Performance

Note: The specific acceptance criteria (e.g., % Essential Agreement, % Category Agreement) and the reported device performance for the Sensititre system with Ciprofloxacin are not provided in the FDA clearance letter. For an AST device, these usually revolve around agreement with a reference method.

Inferred Acceptance Criteria and Hypothetical/Typical Reported Performance for AST Devices:

Metric	Acceptance Criteria (Typical for AST Devices)	Reported Device Performance (Hypothetical/Inferred)
Essential Agreement (EA)	≥ 90.0% for each organism/antibiotic combination	≥ 95.0%
Category Agreement (CA)	≥ 90.0% for each organism/antibiotic combination	≥ 95.0%
Minor Errors (mE)	≤ 7%	≤ 5%
Major Errors (ME)	≤ 3%	≤ 1.5%
Very Major Errors (VME)	≤ 1.5%	≤ 0.5%

Explanation of Terms (for AST devices):

Essential Agreement (EA): The Minimum Inhibitory Concentration (MIC) result of the test device is within ±1 doubling dilution of the reference method's MIC result.
Category Agreement (CA): The interpretive category (Susceptible, Intermediate, Resistant) assigned by the test device matches the interpretive category assigned by the reference method.
Minor Errors (mE): One method (test or reference) interprets as Intermediate, and the other interprets as Susceptible or Resistant.
Major Errors (ME): The test device interprets as Susceptible, but the reference method interprets as Resistant. This is a critical error as it could lead to ineffective treatment.
Very Major Errors (VME): The test device interprets as Resistant, but the reference method interprets as Susceptible. This is also a critical error as it could lead to unnecessary use of broader-spectrum antibiotics.

Study Details (Inferred/Typical for AST Devices)

Sample size used for the test set and the data provenance:
- Sample Size (Test Set): Not specified in the clearance letter. For AST devices, test sets typically involve hundreds to thousands of unique isolates for each organism-antibiotic combination to ensure statistical significance across various resistance mechanisms and phenotypes. This would include both common and challenging strains.
- Data Provenance: Not specified. For FDA submissions, the data provenance is usually a mix of prospective and retrospective clinical isolates, often collected from diverse geographical regions (e.g., multiple centers across the United States) to represent a broad range of clinically relevant strains. The clearance letter mentions testing for "Enterobacterales" and "Pseudomonas aeruginosa," indicating a focus on these specific bacterial groups.
Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
- Number of Experts: Not specified. For AST devices, ground truth is typically established by reference laboratory personnel highly experienced in microbiology, particularly in performing and interpreting reference AST methods (e.g., broth microdilution or agar dilution as per CLSI guidelines). These are not usually "experts" in the sense of clinicians reading images, but rather highly skilled microbiologists.
- Qualifications of Experts: Clinical microbiologists, medical technologists, or laboratory scientists with extensive experience (e.g., 5-10+ years) in a clinical microbiology reference laboratory, proficient in CLSI (Clinical and Laboratory Standards Institute) methodologies for antimicrobial susceptibility testing.
Adjudication method (e.g. 2+1, 3+1, none) for the test set:
- Adjudication Method: Not applicable in the traditional sense for AST devices when comparing to a recognized reference method. The "ground truth" (reference method results) is considered definitive. If initial discrepancies occur between the test device and the reference method, these are typically re-tested by the reference method for confirmation rather than adjudicated by human readers. The reference method (e.g., CLSI broth microdilution) is itself the gold standard.
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:
- MRMC Study: Not applicable. This type of study (MRMC) is relevant for diagnostic imaging devices where human readers interpret images, sometimes with AI assistance. The Sensititre system is an in vitro diagnostic device for antimicrobial susceptibility testing, which directly measures bacterial growth inhibition at various antibiotic concentrations (MICs). It does not involve human "readers" interpreting output in the same way as an imaging device, nor does it typically involve AI assistance in its core mechanism for determining MICs.
If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
- Standalone Performance: Yes, the core evaluation of an AST device like Sensititre is a standalone performance study. The device, when operated according to its instructions for use, generates MIC results and interpretive categories. These results are then compared directly to the reference method. There isn't typically a "human-in-the-loop" for the determination of the MIC or category by the device itself, although human laboratory personnel perform the setup and interpretation of the result in the clinical workflow. The performance data presented in the 510(k) submission would reflect this intrinsic performance of the device.
The type of ground truth used (expert consensus, pathology, outcomes data, etc.):
- Type of Ground Truth: For AST devices, the ground truth is established by a recognized reference method, typically the CLSI (Clinical and Laboratory Standards Institute) reference broth microdilution method or agar dilution method. This is considered the "gold standard" for determining MICs and susceptibility categories. It is a highly standardized and reproducible laboratory procedure.
The sample size for the training set:
- Sample Size (Training Set): Not applicable in the same way as for AI/machine learning algorithms. The Sensititre system is a phenotypic AST system, not an AI-based diagnostic algorithm that requires a "training set" of data. Its "training" is inherent in its design and manufacturing, based on established microbiological principles for detecting bacterial growth and inhibition. Any "development" data would be internal to the manufacturer for optimizing plate format, reagent concentrations, and reading algorithms, but not a "training set" in the context of deep learning.
How the ground truth for the training set was established:
- Ground Truth for Training Set: Not applicable for this type of device. As explained above, the device does not use a "training set" with established ground truth in the AI sense. Its underlying principles are based on microbiological standards and reference methods.

Summary of Information from the FDA Letter:

Device Name: The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Ciprofloxacin in the dilution range of 0.002-64 µg/mL
Intended Use: In vitro diagnostic product for clinical susceptibility testing of non-fastidious isolates, specifically for Ciprofloxacin in the stated dilution range against Enterobacterales (C. freundii, C. koseri, E. cloacae complex, E. coli, K. aerogenes, K. oxytoca, K.pneumoniae, M. morganii, P. mirabilis, P. rettgeri, P. stuartii, P. vulgaris, S. marcescens) and Pseudomonas aeruginosa.
Performance: "demonstrated acceptable performance" (no specific metrics or values provided in the clearance letter).

To obtain the detailed acceptance criteria and study specifics, one would need to review the manufacturer's 510(k) summary, which is typically a public document available through the FDA's 510(k) database.

Summary

FDA 510(k) Clearance Letter - K250990

Page 1

U.S. Food & Drug Administration
10903 New Hampshire Avenue
Silver Spring, MD 20993
www.fda.gov

Doc ID # 04017.07.05

June 30, 2025

Thermo Fisher Scientific
Dylan Staats
Supervisor, R&D, AST and Pharma
1 Thermo Fisher Way
Oakwood Village, Ohio 44146

Re: K250990
Trade/Device Name: The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Ciprofloxacin in the dilution range of 0.002-64 µg/mL
Regulation Number: 21 CFR 866.1640
Regulation Name: Antimicrobial Susceptibility Test Powder
Regulatory Class: Class II
Product Code: JWY, LRG, LTT
Dated: March 31, 2025
Received: April 8, 2025

Dear Dylan Staats:

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 (the 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 available 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.

U.S. Food & Drug Administration
10903 New Hampshire Avenue
Silver Spring, MD 20993
www.fda.gov

June 30, 2025

Thermo Fisher Scientific
Dylan Staats
Supervisor, R&D, AST and Pharma
1 Thermo Fisher Way
Oakwood Village, Ohio 44146

Dear Dylan Staats:

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K250990 - Dylan Staats Page 2

FDA's substantial equivalence determination also included the review and clearance of your Predetermined Change Control Plan (PCCP). Under section 515C(b)(1) of the Act, a new premarket notification is not required for a change to a device cleared under section 510(k) of the Act, if such change is consistent with an established PCCP granted pursuant to section 515C(b)(2) of the Act. Under 21 CFR 807.81(a)(3), a new premarket notification is required if there is a major change or modification in the intended use of a device, or if there is a change or modification in a device that could significantly affect the safety or effectiveness of the device, e.g., a significant change or modification in design, material, chemical composition, energy source, or manufacturing process. Accordingly, if deviations from the established PCCP result in a major change or modification in the intended use of the device, or result in a change or modification in the device that could significantly affect the safety or effectiveness of the device, then a new premarket notification would be required consistent with section 515C(b)(1) of the Act and 21 CFR 807.81(a)(3). Failure to submit such a premarket submission would constitute adulteration and misbranding under sections 501(f)(1)(B) and 502(o) of the Act, respectively.

Additional information about changes that may require a new premarket notification are provided in the FDA guidance documents entitled "Deciding When to Submit a 510(k) for a Change to an Existing Device" (https://www.fda.gov/media/99812/download) and "Deciding When to Submit a 510(k) for a Software Change to an Existing Device" (https://www.fda.gov/media/99785/download).

Your device is also subject to, among other requirements, the Quality System (QS) regulation (21 CFR Part 820), which includes, but is not limited to, 21 CFR 820.30, Design controls; 21 CFR 820.90, Nonconforming product; and 21 CFR 820.100, Corrective and preventive action. Please note that regardless of whether a change requires premarket review, the QS regulation requires device manufacturers to review and approve changes to device design and production (21 CFR 820.30 and 21 CFR 820.70) and document changes and approvals in the device master record (21 CFR 820.181).

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

All medical devices, including Class I and unclassified devices and combination product device constituent parts are required to be in compliance with the final Unique Device Identification System rule ("UDI Rule"). The UDI Rule requires, among other things, that a device bear a unique device identifier (UDI) on its label and package (21 CFR 801.20(a)) unless an exception or alternative applies (21 CFR 801.20(b)) and that the dates on the device label be formatted in accordance with 21 CFR 801.18. The UDI Rule (21 CFR 830.300(a) and 830.320(b)) also requires that certain information be submitted to the Global Unique Device Identification Database (GUDID) (21 CFR Part 830 Subpart E). For additional information on these

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K250990 - Dylan Staats Page 3

requirements, please see the UDI System webpage at https://www.fda.gov/medical-devices/device-advice-comprehensive-regulatory-assistance/unique-device-identification-system-udi-system.

Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR 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-devices/medical-device-safety/medical-device-reporting-mdr-how-report-medical-device-problems.

For comprehensive regulatory information about medical devices and radiation-emitting products, including information about labeling regulations, please see Device Advice (https://www.fda.gov/medical-devices/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-devices/device-advice-comprehensive-regulatory-assistance/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

Page 4

FORM FDA 3881 (6/20) Page 1 of 1 PSC Publishing Services (301) 443-6740 EF

DEPARTMENT OF HEALTH AND HUMAN SERVICES
Food and Drug Administration

Indications for Use

Form Approved: OMB No. 0910-0120
Expiration Date: 06/30/2023
See PRA Statement below.

510(k) Number (if known): K250990

Device Name: The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Ciprofloxacin in the dilution range of 0.002-64 µg/mL

Indications for Use (Describe):

The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System is an in vitro diagnostic product for clinical susceptibility testing of non-fastidious isolates.

This 510(k) is for ciprofloxacin in the dilution range of 0.002-64 µg/mL for testing non-fastidious gram-negative isolates on The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System. Testing is indicated for Enterobacterales and Pseudomonas aeruginosa, as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC) webpage.

The Sensititre 18-24 hour MIC or Breakpoint Susceptibility System with Ciprofloxacin in the dilution range of 0.002-64 µg/mL demonstrated acceptable performance with the following organisms:

Enterobacterales (C. freundii, C. koseri, E. cloacae complex, E. coli, K. aerogenes, K. oxytoca, K.pneumoniae, M. morganii, P. mirabilis, P. rettgeri, P. stuartii, P. vulgaris, S. marcescens)

Pseudomonas aeruginosa

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

☑ Prescription Use (Part 21 CFR 801 Subpart D) ☐ Over-The-Counter Use (21 CFR 801 Subpart C)

CONTINUE ON A SEPARATE PAGE IF NEEDED.

This section applies only to requirements of the Paperwork Reduction Act of 1995.

DO NOT SEND YOUR COMPLETED FORM TO THE PRA STAFF EMAIL ADDRESS BELOW.

The burden time for this collection of information is estimated to average 79 hours per response, including the time to review instructions, search existing data sources, gather and maintain the data needed and complete and review the collection of information. Send comments regarding this burden estimate or any other aspect of this information collection, including suggestions for reducing this burden, to:

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"An agency may not conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a currently valid OMB number."

FORM FDA 3881 (6/20) Page 1 of 1 PSC Publishing Services (301) 443-6740 EF

Regulation Number and Section

§ 866.1640 Antimicrobial susceptibility test powder.

(a)
Identification. An antimicrobial susceptibility test powder is a device that consists of an antimicrobial drug powder packaged in vials in specified amounts and intended for use in clinical laboratories for determining in vitro susceptibility of bacterial pathogens to these therapeutic agents. Test results are used to determine the antimicrobial agent of choice in the treatment of bacterial diseases.(b)
Classification. Class II (performance standards).