HardyDisk Aztreonam/Avibactam 30/20µg (AZA50)

K250454 · Hardy Diagnostics · JTN · May 15, 2025 · Microbiology

Device Facts

• Record ID: K250454
• Device Name: HardyDisk Aztreonam/Avibactam 30/20µg (AZA50)
• Applicant: Hardy Diagnostics
• Product Code: JTN · Microbiology
• Decision Date: May 15, 2025
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 866.1620
• Device Class: Class 2
• 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 Aztreonam/Avibactam 30/20μg (AZA50) for in vitro agar diffusion susceptibility testing is indicated when there is the need to determine the susceptibility of Enterobacterales to Aztreonam/Avibactam, as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC). HardyDisk AST Aztreonam/Avibactam at concentration 30/20μg demonstrated acceptable performance to determine the zone diameter (mm) of Aztreonam/Avibactam against the following microorganisms: Enterobacterales (Citrobacter freundii complex, Escherichia coli, Enterobacter cloacae complex, Klebsiella pneumoniae, Klebsiella oxytoca, Serratia marcescens, Citrobacter koseri, Enterobacter spp., Klebsiella aerogenes, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Providencia rettgeri, Providencia stuartii, Raoultella ornithinolytica, and Serratia spp.)

Device Story

HardyDisk AST Disks are antimicrobial susceptibility test discs used in clinical microbiology laboratories; they facilitate the Kirby-Bauer agar diffusion method. The device consists of paper discs impregnated with a specific concentration of the antimicrobial agent Aztreonam/Avibactam (30/20µg). When placed on inoculated agar plates, the antibiotic diffuses into the medium, inhibiting bacterial growth. The resulting zone of inhibition diameter (measured in mm) is used by clinicians to determine the susceptibility of specific Enterobacterales pathogens to the antibiotic, guiding therapeutic decisions. The device provides a standardized, semi-quantitative assessment of bacterial susceptibility.

Clinical Evidence

No clinical data. Performance supported by analytical data including quality control, disk-to-MIC correlation, and reproducibility studies conducted in accordance with CDER guidance for antimicrobial susceptibility test devices.

Technological Characteristics

Antimicrobial susceptibility test disc; paper disc impregnated with 30/20µg Aztreonam/Avibactam; utilizes agar diffusion (Kirby-Bauer) principle; in vitro diagnostic use.

Indications for Use

Indicated for semi-quantitative in vitro susceptibility testing of Enterobacterales (specific species listed) to Aztreonam/Avibactam using the Kirby-Bauer agar diffusion method. For prescription use only.

Regulatory Classification

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)

{0}

FDA

U.S. FOOD & DRUG

ADMINISTRATION

# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY

ASSAY ONLY

## I Background Information:

A 510(k) Number

K250454

B Applicant

Hardy Diagnostics

C Proprietary and Established Names

HardyDisk Aztreonam/Avibactam 30/20μg (AZA50)

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. Obtain a substantial equivalence determination for aztreonam/avibactam antimicrobial susceptibility test disk.
2. 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:

Aztreonam/Avibactam 30/20μg

### C Type of Test:

Antimicrobial Susceptibility Test Disks

Food and Drug Administration

10903 New Hampshire Avenue

Silver Spring, MD 20993-0002

www.fda.gov

{1}

K250454 - Page 2 of 7

## III Intended Use/Indications for Use:

### A Intended Use(s):

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*.

### 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 Aztreonam/Avibactam 30/20μg (AZA50) for *in vitro* agar diffusion susceptibility testing is indicated when there is the need to determine the susceptibility of Enterobacterales to Aztreonam/Avibactam, as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC).

HardyDisk AST Aztreonam/Avibactam at concentration 30/20μg demonstrated acceptable performance to determine the zone diameter (mm) of Aztreonam/Avibactam against the following microorganisms:

Enterobacterales (*Citrobacter freundii* complex, *Escherichia coli*, *Enterobacter cloacae* complex, *Klebsiella pneumoniae*, *Klebsiella oxytoca*, *Serratia marcescens*, *Citrobacter koseri*, *Enterobacter* spp., *Klebsiella aerogenes*, *Morganella morganii*, *Proteus mirabilis*, *Proteus vulgaris*, *Providencia rettgeri*, *Providencia stuartii*, *Raoultella ornithinolytica*, *Serratia* spp.)

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

Rx - For Prescription Use Only

### D Special Instrument Requirements:

Not applicable.

## IV Device/System Characteristics:

### A Device Description:

{2}

HardyDisk Aztreonam/Avibactam 30/20μg (AZA50) is a high quality 6 mm diameter white filter paper disk that is impregnated with 30μg aztreonam and 20μg avibactam. The disks are clearly marked on both sides with AZA50, designating the agent and the drug content. The disks are supplied in plastic cartridges containing 50 disks each. HardyDisk AST Aztreonam/Avibactam 30/20μg (AZA50) 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 mL of a suitable broth medium. The broth is incubated at 35°C for 2-6 hours to develop a turbidity that exceeds or is equivalent to a 0.5 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 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 make contact with the agar surface. Agar plates are incubated in an ambient air incubator at 35±2°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 qualitatively in accordance with the recognized zone size interpretive criteria for the antimicrobial agent being tested.

## V Substantial Equivalence Information:

### A Predicate Device Name(s):

HardyDisk AST Cefiderocol 30μg (FDC30)

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

K241060

### C Comparison with Predicate(s):

Table 1: Predicate Comparison

| Device & Predicate Device(s): | Device K250454 | Predicate K241060 |
| --- | --- | --- |
| Device Trade Name | HardyDisk AST Aztreonam/Avibactam 30/20μg (AZA50) | HardyDisk AST Cefiderocol 30μg (FDC30) |
| General Device Characteristic Similarities | | |
| Intended Use | Semi-quantitative in | Same |

K250454 - Page 3 of 7

{3}

K250454 - Page 4 of 7
| Device & Predicate Device(s): | Device K250454 | Predicate K241060 |
| --- | --- | --- |
| | vitro 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 | Same |

{4}

| Device & Predicate Device(s): | Device K250454 | Predicate K241060 |
| --- | --- | --- |
| | criteria for the drug. | |
| General Device Characteristic Differences | | |
| Antimicrobial Agent | Aztreonam/Avibactam | Cefiderocol |
| Concentration | 30/20μg | 30μg |

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).

VII Performance Characteristics (if/when applicable):

The premarket submission for HardyDisk AST Aztreonam/Avibactam 30/20μg (AZA50) included a letter dated October 30, 2024, indicating the right of reference to NDA 217906. Descriptive characteristics were sufficient for the HardyDisk AST Aztreonam/Avibactam 30/20μg (AZA50) 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 aztreonam/avibactam.

Data obtained from 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 Enterobacterales 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 Aztreonam/Avibactam 30/20μg (AZA50) 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.

A Analytical Performance:

K250454 - Page 5 of 7

{5}

1. Precision/Reproducibility:
Not applicable

2. Linearity:
Not applicable

3. Analytical Specificity/Interference:
Not applicable

4. Assay Reportable Range:
Not applicable

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

6. Detection Limit:
Not applicable

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

## D Clinical Cut-Off:

Not applicable

K250454 - Page 6 of 7

{6}

# E Expected Values/Reference Range:

The FDA-identified susceptibility interpretive criteria for aztreonam/avibactam are listed below in Table 2.

Table 2. FDA-Identified Disk Diffusion Interpretive Criteria (zone diameter in mm) for Aztreonam/Avibactam

| Organisms | Interpretive Criteria (mm)a | | |
| --- | --- | --- | --- |
| | Susceptible (S) | Intermediate (I) | Resistant (R) |
| Enterobacterales | ≥21 | 18 – 20 | ≤17 |

a FDA STIC Webpage

# 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.

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 Aztreonam/Avibactam $30 / 20\mu \mathrm{g}$ (AZA50) when revised breakpoints for aztreonam/avibactam 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 Aztreonam/Avibactam $30 / 20\mu \mathrm{g}$ (AZA50) device label to include the new breakpoints.

K250454 - Page 7 of 7