← Product Code [JTN](/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JTN) · K253105

# HardyDisk AST Cefiderocol 30µg (FDC30) (K253105)

_Hardy Diagnostics · JTN · Nov 20, 2025 · Microbiology · SESE_

**Canonical URL:** https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JTN/K253105

## Device Facts

- **Applicant:** Hardy Diagnostics
- **Product Code:** [JTN](/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JTN.md)
- **Decision Date:** Nov 20, 2025
- **Decision:** SESE
- **Submission Type:** Traditional
- **Regulation:** 21 CFR 866.1620
- **Device Class:** Class 2
- **Review Panel:** Microbiology
- **Attributes:** PCCP

## Indications for Use

HardyDisk AST disks are used for semi-quantitative in vitro susceptibility testing by the agar diffusion test procedure (Kirby-Bauer) of rapidly growing and certain fastidious bacterial pathogens. Standardized methods for agar diffusion testing have been described for Enterobacterales, Staphylococcus spp., Pseudomonas spp., Acinetobacter spp., Listeria monocytogenes, Enterococcus spp., and by modified procedures, Candida spp., Haemophilus spp., Neisseria gonorrhoeae, Neisseria meningitidis and Streptococcus spp., including Streptococcus pneumoniae. Use of HardyDisk AST Cefiderocol 30μg (FDC30) for in vitro agar diffusion susceptibility testing is indicated when there is the need to determine the susceptibility of Enterobacterales, Pseudomonas aeruginosa, Acinetobacter baumannii complex and Stenotrophomonas maltophilia to cefiderocol, as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC). HardyDisk AST Cefiderocol at concentration 30μg demonstrated acceptable performance to determine the zone diameter (mm) of cefiderocol against the following microorganisms: Enterobacterales (Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Providencia rettgeri, and Serratia marcescens), Pseudomonas aeruginosa, Acinetobacter baumannii complex, Stenotrophomonas maltophilia.

## Device Story

HardyDisk AST Cefiderocol 30μg is a 6mm filter paper disk impregnated with 30μg of cefiderocol; used for semi-quantitative in vitro antimicrobial susceptibility testing via Kirby-Bauer agar diffusion. Clinical laboratory personnel prepare bacterial inoculum from pure cultures to 0.5 McFarland turbidity; streak onto Mueller Hinton agar; apply disks using a dispenser. After 16-18 hours incubation at 35°C, users measure zones of inhibition (mm) and compare against FDA-recognized STIC interpretive criteria to determine susceptibility. Results assist clinicians in selecting appropriate antimicrobial therapy. Includes a Pre-Determined Change Control Plan (PCCP) for updating labeling based on future FDA STIC breakpoint revisions.

## Clinical Evidence

No clinical trials were performed. Evidence relies on analytical performance data including stability, quality control, and disk-to-MIC correlation studies, as well as reference to NDA 209445. Performance was evaluated against FDA-recognized STIC breakpoints.

## Technological Characteristics

Antimicrobial susceptibility test disk; 30µg cefiderocol concentration; paper-based disk for agar diffusion (Kirby-Bauer) testing.

## Regulatory Identification

An antimicrobial susceptibility test disc is a device that consists of antimicrobic-impregnated paper discs used to measure by a disc-agar diffusion technique or a disc-broth elution technique the in vitro susceptibility of most clinically important bacterial pathogens to antimicrobial agents. In the disc-agar diffusion technique, bacterial susceptibility is ascertained by directly measuring the magnitude of a zone of bacterial inhibition around the disc on an agar surface. The disc-broth elution technique is associated with an automated rapid susceptibility test system and employs a fluid medium in which susceptibility is ascertained by photometrically measuring changes in bacterial growth resulting when antimicrobial material is eluted from the disc into the fluid medium. Test results are used to determine the antimicrobial agent of choice in the treatment of bacterial diseases.

## Submission Summary (Full Text)

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>
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FDA U.S. FOOD & DRUG ADMINISTRATION

# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY

ASSAY ONLY

## I Background Information:

A 510(k) Number
K253105

B Applicant
Hardy Diagnostics

C Proprietary and Established Names
HardyDisk AST Cefiderocol 30μg (FDC30)

D Regulatory Information

|  Product Code(s) | Classification | Regulation Section | Panel  |
| --- | --- | --- | --- |
|  JTN | Class II | 21 CFR 866.1620 - Antimicrobial Susceptibility Test Disc | MI - Microbiology  |

## II Submission/Device Overview:

### A Purpose for Submission:

In this Traditional 510(k) submission, Hardy Diagnostics seeks the following:

1. To obtain a substantial equivalence determination for cefiderocol antimicrobial susceptibility test disk for testing with an additional organism (Stenotrophomonas maltophilia).
2. To establish a Pre-Determined Change Control Plan (PCCP) to address future revisions to device labeling in response to breakpoint changes that are recognized on the FDA STIC webpage.

### B Measurand:

Cefiderocol 30μg

### C Type of Test:

Antimicrobial Susceptibility Test Disks

Food and Drug Administration
10903 New Hampshire Avenue
Silver Spring, MD 20993-0002
www.fda.gov

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K253105 - Page 2 of 8

# III Intended Use/Indications for Use:

## A Intended Use(s):

See Indications for Use below.

## B Indication(s) for Use:

HardyDisk AST disks are used for semi-quantitative *in vitro* susceptibility testing by the agar diffusion test procedure (Kirby-Bauer) of rapidly growing and certain fastidious bacterial pathogens. Standardized methods for agar diffusion testing have been described for Enterobacterales, *Staphylococcus* spp., *Pseudomonas* spp., *Acinetobacter* spp., *Listeria monocytogenes*, *Enterococcus* spp., and by modified procedures, *Candida* spp., *Haemophilus* spp., *Neisseria gonorrhoeae*, *Neisseria meningitidis* and *Streptococcus* spp., including *Streptococcus pneumoniae*.

Use of HardyDisk AST Cefiderocol 30μg (FDC30) for *in vitro* agar diffusion susceptibility testing is indicated when there is the need to determine the susceptibility of Enterobacterales, *Pseudomonas aeruginosa*, *Acinetobacter baumannii* complex and *Stenotrophomonas maltophilia* to cefiderocol, as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC).

HardyDisk AST Cefiderocol at concentration 30μg demonstrated acceptable performance to determine the zone diameter (mm) of cefiderocol against the following microorganisms:

- Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella oxytoca*, *Klebsiella pneumoniae*, *Morganella morganii*, *Proteus mirabilis*, *Proteus vulgaris*, *Providencia rettgeri*, and *Serratia marcescens*)
- *Pseudomonas aeruginosa*
- *Acinetobacter baumannii* complex
- *Stenotrophomonas maltophilia*

## C Special Conditions for Use Statement(s):

Rx - For Prescription Use Only

Due to the lack of an interpretive category other than susceptible for cefiderocol with *Stenotrophomonas maltophilia*, the following limitation was included in the device labeling:

The current absence of resistant isolates for *Stenotrophomonas maltophilia* precludes defining any results other than “Susceptible”. Isolates yielding results other than “Susceptible” should be submitted to a reference laboratory for further testing.

## D Special Instrument Requirements:

Not applicable.

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K253105 - Page 3 of 8

# IV Device/System Characteristics:

# A Device Description:

HardyDisk AST Cefiderocol  $30\mu \mathrm{g}$  (FDC30) is a high quality 6 mm diameter white filter paper disk that is impregnated with  $30\mu \mathrm{g}$  cefiderocol. The disks are clearly marked on both sides with FDC30, designating the agent and the drug content. The disks are supplied in plastic cartridges containing 50 disks each. HardyDisk AST Cefiderocol  $30\mu \mathrm{g}$  (FDC30) is intended to be used for in vitro agar diffusion susceptibility testing.

# B Principle of Operation:

The HardyDisk AST Disk is based on the agar diffusion (Kirby-Bauer) methodology. It utilizes dried filter paper disks impregnated with a known concentration of an antimicrobial agent that are placed onto the test medium surface. Three to five similar colonies are transferred to  $4 - 5\mathrm{mL}$  of a suitable broth medium. The broth is incubated at  $35^{\circ}\mathrm{C}$  for 2-6 hours to develop a turbidity that exceeds or is equivalent to a  $0.5\mathrm{McFarland}$  standard. Alternatively, a direct broth or saline suspension of colonies may be prepared from an overnight culture. The final inoculum density should be equivalent to a  $0.5\mathrm{McFarland}$  turbidity standard. The inoculum density may also be standardized photometrically.

Within 15 minutes of inoculum preparation, the Mueller Hinton agar plate is streaked with an inoculated swab to obtain an even inoculation of organism. Disks are aseptically placed onto the agar surface with a disk dispenser and the disks are pressed down with a sterile needle or forceps to contact the agar surface. Agar plates are incubated in an ambient air incubator at  $35 \pm 2^{\circ} \mathrm{C}$  for 16-18 hours.

After incubation, the agar medium is examined for a zone of inhibition around the disks. The zones of inhibition are measured to the nearest millimeter and interpreted by comparison to recognized zone size interpretive criteria for the antimicrobial agent being tested.

# V Substantial Equivalence Information:

# A Predicate Device Name(s):

HardyDisk AST Gepotidacin  $10\mu \mathrm{g}$  (GEP10)

# B Predicate 510(k) Number(s):

K241060

# C Comparison with Predicate(s):

|  Device & Predicate Device(s): | Device K253105 | Predicate K241060  |
| --- | --- | --- |
|  Device Trade Name | HardyDisk AST Cefiderocol 30μg (FDC30) | HardyDisk AST Cefiderocol 30μg (FDC30)  |
|  General Device Characteristic Similarities  |   |   |
|  Intended Use | Semi-quantitative in vitro | Same  |

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K253105 - Page 4 of 8
|  Device & Predicate Device(s): | Device K253105 | Predicate K241060  |
| --- | --- | --- |
|   | susceptibility testing by the agar diffusion test procedure (Kirby-Bauer) of rapidly growing and certain fastidious bacterial pathogens. |   |
|  Test Method | Antimicrobial susceptibility testing using paper disks impregnated with an antimicrobial agent | Same  |
|  Methodology | Kirby-Bauer Disk Diffusion Susceptibility Test Protocol requires the user to determine categorical interpretations (S/I/R) using the measured zone diameters. | Same  |
|  Inoculum | Prepared from pure isolated colonies to match the turbidity equivalent of a 0.5 McFarland in Tryptic Soy Broth. | Same  |
|  Inoculum Method | Dip a sterile swab into the prepared inoculum and streak an appropriate agar plate’s surface three times. Add the disks impregnated with the antimicrobial agent to the surface of the plate. The temperature, atmospheric conditions and duration of incubation is dependent on the organism tested. | Same  |
|  Reading Method | The user will interpret the zone diameters according to the established interpretive criteria for the drug. | Same  |
|  Antimicrobial Agent | Cefiderocol | Same  |
|  Concentration | 30μg | Same  |
|  General Device Characteristic Differences  |   |   |
|  Test Organisms | Enterobacterales (Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella | Gram-negative bacteria: Escherichia coli Enterobacter cloacae complex  |

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|  Device & Predicate Device(s): | Device K253105 | Predicate K241060  |
| --- | --- | --- |
|   | pneumoniae, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Providencia rettgeri, and Serratia marcescens) | Klebsiella pneumoniae
Proteus mirabilis
Pseudomonas aeruginosa
Acinetobacter baumannii complex
Serratia marcescens
Citrobacter freundii complex
Citrobacter koseri
Klebsiella aerogenes
Klebsiella oxytoca
Morganella morganii
Proteus vulgaris
Providencia rettgeri  |
|   | Pseudomonas aeruginosa
Acinetobacter baumannii complex
Stenotrophomonas maltophilia |   |

Predetermined Change Control Plan (PCCP):

To support the implementation of changes to FDA-recognized susceptibility test interpretive criteria (i.e., breakpoints), this submission included a predetermined change control plan (PCCP) that was reviewed and accepted by FDA. This PCCP addresses future revisions to device labeling in response to breakpoint changes that are recognized on the FDA STIC webpage (https://www.fda.gov/Drugs/DevelopmentApprovalProcess/DevelopmentResources/ucm410971.htm). The PCCP outlined the specific procedures and acceptance criteria that Hardy Diagnostics intends to use to evaluate the HardyDisk AST Cefiderocol 30μg (FDC30) when revised breakpoints for cefiderocol are published on the FDA STIC webpage. The PCCP included with the submission indicated that if specific criteria are met, Hardy Diagnostics will update the HardyDisk AST Cefiderocol 30μg (FDC30) device label to include the new breakpoints.

VI Standards/Guidance Documents Referenced:

- CLSI M02-14th ed. Performance Standards for Antimicrobial Disk Susceptibility Tests (March 2024).
- CLSI M100-35th ed. Performance Standards for Antimicrobial Susceptibility Testing (January 2025).

K253105 - Page 5 of 8

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K253105 - Page 6 of 8

# VII Performance Characteristics (if/when applicable):

The premarket submission for HardyDisk Cefiderocol 30µg (FDC30) included a letter dated December 14, 2023, indicating the right of reference to NDA 209445. Descriptive characteristics were sufficient for the HardyDisk Cefiderocol 30µg (FDC30) disk based on data from microbiology disk studies evaluated by CDER which were used to generate the breakpoints identified by FDA on the susceptibility test interpretive criteria (STIC) webpage. In addition, CDER concurred with the disk QC ranges that were established by CLSI. The disk data used to support this submission included data from testing organisms shown to be active in vitro and/or in clinical infections within the spectrum of activity of cefiderocol.

Data obtained from stability, quality control, disk to MIC correlation, and reproducibility (from disk content optimization) studies were generated in accordance with the CDER Clinical/Antimicrobial guidance, Microbiology Data for Systemic Antibacterial Drugs-Development, Analysis, and Presentation to ensure precise, accurate, and reproducible results.

For this review, the interpretive criteria are applied to Stenotrophomonas maltophilia according to the FDA STIC website. As required under 511A(2)(2)(B) of the Federal Food, Drug and Cosmetic Act, the following statement is included in the Precautions section of the HardyDisk AST Cefiderocol 30µg package insert:

Per the FDA-Recognized Susceptibility Test Interpretive Criteria website, the safety and efficacy of antimicrobial drugs, for which antimicrobial susceptibility is tested by this AST device, may or may not have been established in adequate and well-controlled clinical trials for treating clinical infections due to microorganisms outside of those found in the indications and usage in the drug label. The clinical significance of susceptibility information in those instances is unknown. The approved labeling for specific antimicrobial drugs provides the uses for which the antimicrobial drug is approved.

# Non-susceptible Isolates Tested:

Due to the lack of an interpretive category other than susceptible for cefiderocol with Stenotrophomonas maltophilia, the following limitation was included in the device labeling:

The current absence of resistant isolates for Stenotrophomonas maltophilia precludes defining any results other than "Susceptible". Isolates yielding results other than "Susceptible" should be submitted to a reference laboratory for further testing.

# A Analytical Performance:

1. Precision/Reproducibility:
Not applicable.

2. Linearity:
Not applicable.

3. Analytical Specificity/Interference:
Not applicable.

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4. Detection Limit and Assay Reportable Range:
Not applicable.

5. Traceability, Stability, Expected Values (Controls, Calibrators, or Methods):
Not applicable.

6. Assay Cut-Off:
Not applicable.

## B Comparison Studies:

1. Method Comparison with Predicate Device:
Not applicable.

2. Matrix Comparison:
Not applicable.

## C Clinical Studies:

1. Clinical Sensitivity:
Not applicable.

2. Clinical Specificity:
Not applicable.

3. Clinical Cut-Off:
Not applicable.

4. Other Clinical Supportive Data (When 1. and 2. Are Not Applicable):
Not applicable.

## D Expected Values/Reference Range:

Not applicable.

## E Expected Values/Reference Range:

The FDA-recognized susceptibility interpretive criteria for cefiderocol are listed below in Table 1.

K253105 - Page 7 of 8

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Table 1. FDA-Recognized Disk Diffusion Interpretive Criteria (zone diameter in mm) for Cefiderocol

|  Organisms | Interpretive Criteria (mm)a  |   |   |
| --- | --- | --- | --- |
|   |  Susceptible (S) | Intermediate (I) | Resistant I  |
|  Enterobacterales | ≥16 | 9–15 | ≤8  |
|  Pseudomonas aeruginosa | ≥22 | 13–21 | ≤12  |
|  Acinetobacter baumannii complex | ≥19 | 12–18 | ≤11  |
|  Stenotrophomonas maltophilia | ≥17 | - | -  |

a According to the FDA STIC Webpage, https://www.fda.gov/drugs/development-resources/fda-recognized-antimicrobial-susceptibility-test-interpretive-criteria

## VIII Proposed Labeling:

The labeling supports the finding of substantial equivalence for this device.

## IX Conclusion:

The submitted information in this premarket notification is complete and supports a substantial equivalence decision.

K253105 - Page 8 of 8

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**Source:** [https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JTN/K253105](https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JTN/K253105)

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