ASTar BC G- Kit

K253573 · Q-Linea AB · SAN · Apr 15, 2026 · Microbiology

Device Facts

• Record ID: K253573
• Device Name: ASTar BC G- Kit
• Applicant: Q-Linea AB
• Product Code: SAN · Microbiology
• Decision Date: Apr 15, 2026
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 866.1650
• Device Class: Class 2
• Attributes: PCCP

Indications for Use

The ASTar System is intended to be used for the automated quantitative susceptibility testing for most clinically significant microorganisms. The ASTar System does not provide organism identification. The ASTar System, comprised of the ASTar Instrument with the ASTar BC G– Kit (ASTar BC G– Consumable kit, ASTar BC G– Frozen Insert, and ASTar BC G– Kit software), utilizes high-speed, time-lapse microscopy imaging of bacteria for the in vitro, quantitative determination of antimicrobial susceptibility of on-panel gram-negative bacteria. The test is performed directly on positive blood culture samples signaled as positive by a continuous monitoring blood culture system and confirmed to contain Gram-negative bacilli by Gram stain. Organism identification is required for AST result interpretation and reporting. Test results from the ASTar BC G– Kit should be interpreted in conjunction with other clinical and laboratory findings. Standard laboratory protocols for processing positive blood cultures should be followed to ensure availability of isolates for supplemental testing. Sub-culturing is necessary to support further testing for: bacteria and antimicrobials not on the ASTar BC G– panel, where inconclusive results are obtained, epidemiologic testing, recovery of organisms present in microbial samples, and susceptibility testing of bacteria in polymicrobial samples.

Device Story

ASTar System performs automated, quantitative antimicrobial susceptibility testing (AST) on positive blood culture samples containing Gram-negative bacteria. Input: ~1 mL positive blood culture sample. Process: Instrument purifies/quantifies bacteria, adjusts inoculum concentration, and transfers to ASTar Disc; utilizes high-speed, time-lapse microscopy imaging to monitor bacterial growth response to various antimicrobial concentrations. Output: Minimum Inhibitory Concentration (MIC) and qualitative susceptibility results (S, I, SDD, R). Used in clinical laboratories; operated by laboratory personnel. Results interpreted alongside clinical findings to guide antibiotic therapy. Benefits: Rapid AST results (approx. 6 hours) directly from blood culture, enabling faster targeted treatment.

Clinical Evidence

Clinical study evaluated 630 samples (167 fresh, 221 clinical stock, 242 challenge isolates) across three sites. Performance compared to frozen broth microdilution (BMD) per CLSI M07. Metrics included Essential Agreement (EA), Category Agreement (CA), and discrepancy rates (VMJ, MAJ, MIN). Overall performance met acceptance criteria for most antimicrobial/organism combinations. Limitations identified for specific combinations due to insufficient resistant isolates or performance deviations, addressed via labeling restrictions or concentration-specific limitations.

Technological Characteristics

Fully automated cellular analysis system using high-speed, time-lapse microscopy imaging. Consumables: ASTar Cartridge (sample prep) and ASTar Disc (incubation/imaging). Connectivity: Standalone instrument. Software: Version 2, rule-based and image analysis algorithms for MIC determination. Sterilization: Not specified.

Indications for Use

Indicated for quantitative antimicrobial susceptibility testing of Gram-negative bacteria (Acinetobacter spp., Enterobacterales, Pseudomonas aeruginosa) from positive blood culture samples confirmed by Gram stain. Requires organism identification for interpretation. Prescription use only.

Regulatory Classification

Identification

A cellular analysis system for multiplexed antimicrobial susceptibility testing is a multiplex qualitative and/or quantitative in vitro diagnostic device intended for the identification and determination of the antimicrobial susceptibility results of organisms detected in samples from patients with suspected microbial infections. This device is intended to aid in the determination of antimicrobial susceptibility or resistance when used in conjunction with other laboratory findings.

Special Controls

*Classification.* Class II (special controls). The special controls for this device are:(1) Design verification and validation must include: (i) Detailed device description documentation, including the device components, ancillary reagents required but not provided, a detailed explanation of the methodology, including primer/probe sequence, design, rationale for sequence selection, and details of the antimicrobial agents, as applicable. (ii) Detailed documentation from the following analytical and clinical performance studies: limit of detection, inclusivity, precision, reproducibility, interference, cross-reactivity, carryover, and cross-contamination, quality control and additional studies, as applicable to specimen type and assay intended use. (iii) Detailed documentation from an appropriate clinical study. The study, performed on a study population consistent with the intended use population, must compare the device performance to results obtained from well-accepted reference methods. (iv) Detailed documentation for device software, including software applications and hardware-based devices that incorporate software. (2) The labeling required under § 809.10(b) of this chapter must include: (i) Limitations and protocols regarding the need for correlation of results by standard laboratory procedures, as applicable. (ii) A detailed explanation of the interpretation of results and acceptance criteria. (iii) A detailed explanation of the principles of operation and procedures for assay performance and troubleshooting.

Predicate Devices

• ASTar BC G- Kit with ASTar Instrument (K221688)

Submission Summary (Full Text)

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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

K253573

B Applicant

Q-linea AB

C Proprietary and Established Names

ASTar BC G- Kit

D Regulatory Information

| Product Code(s) | Classification | Regulation Section | Panel |
| --- | --- | --- | --- |
| SAN | Class II | 21 CFR 866.1650 - A Cellular Analysis System For Multiplexed Antimicrobial Susceptibility | MI - Microbiology |
| LON | Class II | 21 CFR 866.1645 - Fully automated short-term incubation cycle antimicrobial susceptibility system | MI - Microbiology |

# II Submission/Device Overview:

# A Purpose for Submission:

To obtain a substantial equivalence determination for the ASTar BC G- Kit, previously cleared for use with the ASTar Instrument in K221688, to:

1. Expand the Indications for Use to include testing with cefotaxime, cefoxitin, ceftolozane-tazobactam, ceftriaxone, and ertapenem
2. Expand the Indications for Use to include testing of additional species with FDA STIC-recognized breakpoints for previously claimed drugs
3. Remove performance limitations for aztreonam, cefepime, piperacillin-tazobactam, and tobramycin

Food and Drug Administration

10903 New Hampshire Avenue

Silver Spring, MD 20993-0002

www.fda.gov

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4. Reanalyze data to establish performance with updated FDA STIC-recognized breakpoints for amikacin, cefepime, gentamicin, and tobramycin

5. Establish a Predetermined 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:**

| Antimicrobial | ASTar Reporting Range (μg/mL) | | |
| --- | --- | --- | --- |
| | Acinetobacter spp. | Enterobacterales | P. aeruginosa |
| Amikacin | ≤2 to ≥256 | ≤2 to ≥256 | - |
| Ampicillin-sulbactam | ≤1 to ≥128 | ≤1 to ≥128 | - |
| Aztreonam | - | ≤0.5 to ≥128 | ≤0.5 to ≥128 |
| Cefazolin | - | ≤0.25 to ≥32 | - |
| Cefepime | - | ≤0.25 to ≥128 | ≤0.25 to ≥128 |
| Cefotaxime | - | ≤0.25 to ≥16 | - |
| Cefoxitin | - | ≤1 to >128 | - |
| Ceftazidime | ≤0.5 to ≥128 | ≤0.5 to ≥128 | - |
| Ceftazidime-avibactam | - | ≤1 to ≥64 | ≤0.125 to ≥64 |
| Ceftolozane-tazobactam | - | ≤0.25 to ≥64 | ≤0.25 to ≥64 |
| Ceftriaxone | - | ≤0.25 to ≥16 | - |
| Cefuroxime | - | ≤1 to >128 | - |
| Ciprofloxacin | - | ≤0.125 to ≥16 | ≤0.125 to ≥16 |
| Ertapenem | - | ≤0.06 to ≥16 | - |
| Gentamicin | - | ≤0.25 to ≥64 | - |
| Levofloxacin | - | ≤0.125 to ≥32 | ≤0.125 to ≥32 |
| Meropenem | ≤0.06 to ≥128 | ≤0.125 to ≥64 | ≤0.06 to ≥128 |
| Meropenem-vaborbactam | - | ≤0.5 to ≥64 | - |
| Piperacillin-tazobactam | ≤1 to ≥512 | ≤1 to ≥512 | - |
| Tobramycin | - | ≤0.125 to ≥64 | ≤0.125 to ≥64 |
| Trimethoprim/sulfamethoxazole | - | ≤0.25 to ≥16 | - |

Please refer to K221688 Decision Summary for more information of previously cleared antimicrobials.

# **C Type of Test:**

Quantitative antimicrobial susceptibility test (AST) system that utilizes high-speed, time-lapse microscopy imaging of organisms in positive blood culture samples to determine the minimum inhibitory concentration (MIC) of specific antimicrobial-organism combinations.

# **III Intended Use/Indications for Use:**

# **A Intended Use(s):**

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The ASTar System is intended to be used for the automated quantitative susceptibility testing for most clinically significant microorganisms. The ASTar System does not provide organism identification.

## **B Indication(s) for Use:**

The ASTar System, comprised of the ASTar Instrument with the ASTar BC G– Kit (ASTar BC G– Consumable kit, ASTar BC G– Frozen Insert, and ASTar BC G– Kit software), utilizes high-speed, time-lapse microscopy imaging of bacteria for the in vitro, quantitative determination of antimicrobial susceptibility of on-panel gram-negative bacteria. The test is performed directly on positive blood culture samples signaled as positive by a continuous monitoring blood culture system and confirmed to contain Gram-negative bacilli by Gram stain. Organism identification is required for AST result interpretation and reporting.

Test results from the ASTar BC G– Kit should be interpreted in conjunction with other clinical and laboratory findings. Standard laboratory protocols for processing positive blood cultures should be followed to ensure availability of isolates for supplemental testing. Sub-culturing is necessary to support further testing for: bacteria and antimicrobials not on the ASTar BC G– panel, where inconclusive results are obtained, epidemiologic testing, recovery of organisms present in microbial samples, and susceptibility testing of bacteria in polymicrobial samples.

Testing is indicated for *Acinetobacter* spp. Enterobacterales, and *Pseudomonas aeruginosa*, as recognized by the FDA Susceptibility Test Interpretive Criteria (STIC). The ASTar BC G- Kit with ASTar system has demonstrated acceptable performance with the following organisms:

**Amikacin:** *Acinetobacter* spp. (*Acinetobacter baumannii* complex), Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Morganella morganii*, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*)

**Ampicillin:** Enterobacterales (*Escherichia coli*, *Proteus mirabilis*)

**Ampicillin-sulbactam:** *Acinetobacter* spp. (*Acinetobacter baumannii* complex), Enterobacterales (*Citrobacter koseri*, *Escherichia coli*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Morganella morganii*, *Proteus mirabilis*, *Proteus vulgaris*)

**Aztreonam:** Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Morganella morganii*, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*) and *Pseudomonas aeruginosa*

**Cefazolin:** Enterobacterales (*Citrobacter koseri*, *Escherichia coli*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Proteus mirabilis*)

**Cefepime:** Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*) and *Pseudomonas aeruginosa*

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**Cefotaxime:** Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*)

**Cefoxitin:** Enterobacterales (*Citrobacter koseri*, *Escherichia coli*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Proteus mirabilis*)

**Ceftazidime:** *Acinetobacter* spp. (*Acinetobacter baumannii* complex), Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Morganella morganii*, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*)

**Ceftazidime-avibactam:** Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Morganella morganii*, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*) and *Pseudomonas aeruginosa*

**Ceftolozane-tazobactam:** Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*) and *Pseudomonas aeruginosa*

**Ceftriaxone:** Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*)

**Cefuroxime:** Enterobacterales (*Citrobacter koseri*, *Escherichia coli*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Proteus mirabilis*)

**Ciprofloxacin:** Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Morganella morganii*, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*) and *Pseudomonas aeruginosa*

**Ertapenem:** Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*)

**Gentamicin:** Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Morganella morganii*, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*)

**Levofloxacin:** Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Morganella morganii*, *Proteus mirabilis*, *Proteus vulgaris*, *Serratia marcescens*) and *Pseudomonas aeruginosa*

**Meropenem:** *Acinetobacter* spp. (*Acinetobacter baumannii* complex), Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Enterobacter cloacae* complex, *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella oxytoca*, *Klebsiella pneumoniae* group, *Morganella*

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morganii, Proteus mirabilis, Proteus vulgaris, Serratia marcescens), and Pseudomonas aeruginosa

**Meropenem-vaborbactam:** Enterobacterales (Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae group, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Serratia marcescens)

**Piperacillin-tazobactam:** Acinetobacter spp. (Acinetobacter baumannii complex) and Enterobacterales (Citrobacter freundii complex, Citrobacter koseri, Escherichia coli, Klebsiella aerogenes, Klebsiella pneumoniae group, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Serratia marcescens)

**Tigecycline:** Enterobacterales (Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae group, Serratia marcescens)

**Tobramycin:** Enterobacterales (Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae group, Proteus mirabilis, Proteus vulgaris) and Pseudomonas aeruginosa

**Trimethoprim-sulfamethoxazole:** Enterobacterales (Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae group, Morganella morganii, Proteus vulgaris)

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

Rx - For Prescription Use Only

#### General Limitations

- The ASTar BC G- kit can only be used with the ASTar Instrument.
- The ASTar BC G- kit has not been evaluated for specimens other than positive blood culture.
- The performance of the ASTar BC G- kit has only been evaluated using the following blood culture bottles:

- bioMérieux BACT/ALERT FA Plus Aerobic
- bioMérieux BACT/ALERT FN Plus Anaerobic
- bioMérieux BACT/ALERT PF Plus
- bioMérieux BACT/ALERT SN Standard Anaerobic
- bioMérieux BACT/ALERT SA Standard Aerobic
- BD BACTEC Peds Plus
- BD BACTEC Lytic Anaerobic
- BD BACTEC Plus Anaerobic
- BD BACTEC Plus Aerobic
- BD BACTEC Standard Aerobic
- BD BACTEC Standard Anaerobic

- The ASTar BC G– Kit should not be used with blood culture bottles containing charcoal.
- Positive blood cultures should be tested immediately after a positive flag, where possible. A

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16-hour sample stability claim is included in case of instrument errors or if re-testing is needed.

- Failure to observe proper procedures for sample collection, preparation, storage, handling and/or transportation may cause incorrect results.
- AST results should not be reported if two or more species are identified in a patient sample.
- If an AST result is not provided by the ASTar BC G- Kit, susceptibility testing must be performed using an alternate method.
- Subculturing of positive blood culture is necessary for organisms not claimed by the ASTar BC G- Kit and for antimicrobial agents not included on the ASTar panel.

### Antimicrobial Susceptibility Testing (AST) Limitations

The following limitations were added to the device labeling based on performance demonstrated in the current submission:

- Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Cefepime: Morganella morganii
- Cefotaxime: Acinetobacter baumannii complex, Escherichia coli when the ASTar MIC is 1 μg/mL due to one very major discrepancy, Klebsiella aerogenes, Morganella morganii
- Cefoxitin: Klebsiella oxytoca when the ASTar MIC is 4 μg/mL due to one very major discrepancy, Morganella morganii, Proteus vulgaris
- Ceftazidime: Morganella morganii when the ASTar MIC is 64 μg/mL due to one major discrepancy, Pseudomonas aeruginosa
- Ceftolozane-tazobactam: Klebsiella aerogenes, Morganella morganii
- Ceftriaxone: Proteus vulgaris when the ASTar MIC is 4 μg/mL due to one very major discrepancy, Morganella morganii
- Cefuroxime: Enterobacter cloacae complex, Klebsiella aerogenes
- Ertapenem: Klebsiella aerogenes, Klebsiella pneumoniae group when the ASTar MIC is 0.5 μg/mL due to one very major discrepancy, Morganella morganii
- Gentamicin: Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella pneumoniae group when the ASTar MIC is 2 μg/mL due to one very major discrepancy
- Meropenem: Escherichia coli when the ASTar MIC is either 0.5 or 1 μg/mL due to three very major discrepancies, Enterobacter cloacae complex when the ASTar MIC is 0.5 μg/mL or 1 μg/mL due to two very major discrepancies
- Piperacillin-tazobactam: Enterobacter cloacae complex, Klebsiella oxytoca, Pseudomonas aeruginosa
- Tobramycin: Enterobacter cloacae complex when the ASTar MIC is 8 μg/mL due to one major discrepancy, Klebsiella oxytoca when the ASTar MIC is 32 μg/mL due to one major discrepancy, Morganella morganii, Serratia marcescens
- Trimethoprim-sulfamethoxazole: Proteus mirabilis, Serratia marcescens

- Perform an alternate method of testing prior to reporting results when a resistant result is obtained for the following organisms, if critical to patient care:

- Trimethoprim-sulfamethoxazole: Klebsiella pneumoniae group

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• The ability of the ASTar system to detect resistance in the following antimicrobial/organism combinations is unknown because of an insufficient number of resistant isolates were available during the clinical study:

○ Amikacin: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Klebsiella aerogenes, Klebsiella oxytoca, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Serratia marcescens

○ Ampicillin-sulbactam: Citrobacter koseri, Klebsiella oxytoca, Proteus mirabilis, Proteus vulgaris

○ Aztreonam: Citrobacter freundii complex, Citrobacter koseri, Klebsiella aerogenes, Klebsiella oxytoca, Proteus mirabilis, Proteus vulgaris, Serratia marcescens

○ Cefepime: Citrobacter freundii complex, Klebsiella aerogenes, Klebsiella oxytoca, Proteus mirabilis, Proteus vulgaris, Serratia marcescens

○ Cefotaxime: Citrobacter freundii complex, Proteus vulgaris

○ Ceftazidime: Citrobacter freundii complex, Klebsiella oxytoca, Proteus mirabilis, Proteus vulgaris, Serratia marcescens

○ Ceftazidime-avibactam: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Klebsiella aerogenes, Klebsiella oxytoca, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Pseudomonas aeruginosa, Serratia marcescens

○ Ceftolozane-tazobactam: Citrobacter freundii complex, Proteus vulgaris, Serratia marcescens

○ Ceftriaxone: Citrobacter freundii complex, Proteus vulgaris

○ Cefuroxime: Klebsiella oxytoca, Proteus mirabilis

○ Ciprofloxacin: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Klebsiella aerogenes, Klebsiella oxytoca, Proteus vulgaris, Pseudomonas aeruginosa, Serratia marcescens

○ Ertapenem: Citrobacter freundii complex, Proteus mirabilis, Proteus vulgaris

○ Gentamicin: Citrobacter freundii complex, Citrobacter koseri, Klebsiella oxytoca, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Serratia marcescens

○ Levofloxacin: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Klebsiella aerogenes, Klebsiella oxytoca, Proteus mirabilis, Proteus vulgaris, Pseudomonas aeruginosa, Serratia marcescens

○ Meropenem: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Pseudomonas aeruginosa, Serratia marcescens

○ Meropenem-vaborbactam: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae group, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Serratia marcescens

○ Piperacillin-tazobactam: Citrobacter freundii complex, Citrobacter koseri, Proteus mirabilis, Proteus vulgaris, Serratia marcescens

○ Tigecycline: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae group, Serratia marcescens

○ Tobramycin: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Klebsiella aerogenes, Proteus mirabilis, Proteus vulgaris

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○ Trimethoprim-sulfamethoxazole: Citrobacter freundii complex, Citrobacter koseri, Klebsiella aerogenes, Klebsiella oxytoca, Proteus vulgaris, Serratia marcescens

# D Special Instrument Requirements:

Test with the following software or later version:

ASTar BC G- Kit Software version 2.1

ASTar Application Computer Image version 1.6

ASTar Instrument Computer Image version 1.8

# IV Device/System Characteristics:

# A Device Description:

ASTar System is a fully automated system for antimicrobial susceptibility testing (AST). It consists of the ASTar Instrument in combination with dedicated application kits. The ASTar BC G- Kit contains the ASTar BC G- Consumable kit (discs and cartridges), ASTar BC G- Frozen insert, and ASTar BC G- Kit software which must be installed on the instrument to process the kit. The frozen insert is a single-use plastic container with frozen reagents and is added to the cartridge prior to sample run. The system prepares an inoculum for AST and utilizes high-speed, time-lapse microscopy imaging of pathogens in broth microdilution to determine minimum inhibitory concentration (MIC) and qualitative susceptibility results for samples. Organism identification by an alternate method is required to be entered into the ASTar Instrument for AST results to be reported.

The ASTar instrument is designed to carry out sample preparation of up to six samples in parallel using a dedicated ASTar Cartridge consumable for each sample. In the subsequent AST culturing step, the instrument transfers the prepared sample into a second dedicated consumable, referred to as the ASTar Disc. Up to 12 discs can be incubated simultaneously in the system with samples at different stages of the processing procedure. New samples can be loaded in a random-access manner when there are available slots. The operator interacts with the instrument via the touchscreen display to run test samples.

ASTar BC G- Kit is used for in vitro determination of AST results for commonly isolated bacteria derived from positive blood culture samples confirmed by Gram stain to be Gramnegative bacteria. To start an analysis, approximately 1 mL of a positive blood culture is pipetted into the ASTar Cartridge by the operator and loaded into the system. The instrument purifies and quantifies the bacteria, and the bacterial concentration is adjusted to the appropriate inoculum concentration. The bacterial suspensions are transferred automatically to the ASTar Disc and antimicrobial susceptibility testing is performed based on a defined protocol. The system generates an MIC and further qualitative susceptibility results (i.e., S, I, R) for the tested antimicrobials, where applicable. The ASTar System with the ASTar BC G- Kit can determine the MIC of various antimicrobials when tested against specific organisms with FDA Susceptibility Testing Interpretive Criteria (STIC) breakpoints.

# B Principle of Operation:

The ASTar BC G- kit, along with the ASTar Instrument, constitute a fully automated system for the in vitro determination of antimicrobial susceptibility of Gram-negative bacilli present in

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positive blood culture bottles (BCBs). The instrument provides inoculum preparation for AST and utilizes high-speed, time-lapse microscopy imaging of pathogens in broth microdilution to determine minimum inhibitory concentration (MIC) and qualitative susceptibility results.

The consumable kit consists of a preparation cartridge and a disk with dried antimicrobials in 1:2 dilution series. Approximately 1 mL of a positive blood culture, confirmed Gram-negative by Gram stain, is pipetted into the ASTar Cartridge by the operator and loaded into the system. All other procedures are automated. Briefly, the ASTar purifies and quantifies the bacteria from the BCB. Resin particles are removed by filtration and human-derived cells are lysed by adding lysis buffer to the sample. Bacteria are separated from the lysate by filtering and captured on a filter membrane. The pathogens present in the aliquot are resuspended in culture medium. Bacterial concentration is determined by mixing an aliquot of bacterial suspension with staining medium (fluorescent dye). The stained aliquot is added to the disc and the concentration is determined by fluorescent imaging at one wavelength. Based on the concentration, the instrument creates aliquots at a pre-defined inoculum concentration (typically $5 \times 10^5$ CFU/mL). The disc is placed in an incubator carousel and each well is imaged at specified time intervals using a high-speed optical microscopy system. Bacterial growth and response to relevant concentrations of different antimicrobial drugs are measured throughout the incubation period using the optical detection system in combination with image analysis algorithms. Next, the images are analyzed for bacterial content over time, and the system generates the MIC and qualitative susceptibility results (i.e., S, I, R) for the tested antimicrobials, where applicable. The qualitative results are determined based on established breakpoints. The system allows culturing and analysis to start in the absence of bacterial ID, which is only needed for final interpretation and reporting. Results are available within approximately 6 hours.

## V Substantial Equivalence Information:

### A Predicate Device Name(s):

ASTar BC G- Kit and ASTar Instrument

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

K221688

### C Comparison with Predicate(s):

| Device & Predicate Device(s): | K253573 (Device) | K221688 (Predicate) |
| --- | --- | --- |
| Device Trade Name | ASTar BC G- Kit | ASTar BC G- Kit and ASTar Instrument |
| **General Device Characteristic Similarities** | | |
| Intended Use | The ASTar System is intended to be used for the automated quantitative susceptibility testing for most clinically significant microorganisms. The ASTar System | Same |

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| Device & Predicate Device(s): | K253573 (Device) | K221688 (Predicate) |
| --- | --- | --- |
| | does not provide organism identification. The ASTAar System, comprised of the ASTar Instrument with the ASTar BC G– Kit (ASTar BC G– Consumable kit, ASTar BC G– Frozen Insert, and ASTar BC G– Kit software), utilizes high-speed, time-lapse microscopy imaging of bacteria for the *in vitro*, quantitative determination of antimicrobial susceptibility of on-panel gram-negative bacteria. The test is performed directly on positive blood culture samples signaled as positive by a continuous monitoring blood culture system and confirmed to contain gram- negative bacilli by Gram stain. Organism identification is required for AST result interpretation and reporting. Test results from the ASTar BC G– Kit should be interpreted in conjunction with other clinical and laboratory findings. Standard laboratory protocols for processing positive blood cultures should be followed to ensure availability of isolates for supplemental testing. Sub-culturing is necessary to support further testing for: bacteria and antimicrobials not on the ASTar BC G– panel, where inconclusive results are obtained, epidemiologic testing, recovery of organisms present in microbial samples, and susceptibility testing of bacteria in polymicrobial samples. | |
| Blood Culture Bottle Types | BD BACTEC: Standard Aerobic, Anaerobic; Lytic Anaerobic; Peds Plus, Plus Aerobic, Anaerobic BioMeriuex BacT/ALERT: Standard Aerobic, Anaerobic; Plus Aerobic, | Same |

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| **Device & Predicate Device(s):** | **K253573 (Device)** | **K221688 (Predicate)** |
| --- | --- | --- |
| | Anaerobic; PF Plus | |
| Technology | High-speed, time-lapse microscopy imaging | Same |
| Sample Type | Positive blood culture | Same |
| Sample Prep | Direct from sample. No manual McFarland preparation required | Same |
| Inoculation Method | Automated | Same |
| Read Method | Automated | Same |
| IVD Function | Provides AST results only. ID is required but provided by alternative method | Same |
| Instrument Platform | ASTar Instrument | Same |
| **General Device Characteristic Differences** | | |
| Antimicrobial Panel | Amikacin Ampicillin Ampicillin-sulbactam Aztreonam Cefazolin Cefepime Cefotaxime Cefoxitin Ceftazidime Ceftazidime-avibactam Ceftolozane-tazobactam Ceftriaxone Cefuroxime Ciprofloxacin Ertapenem Gentamicin Levofloxacin Meropenem Meropenem-vaborbactam Piperacillin-tazobactam Tigecycline Tobramycin Trimethoprim-sulfamethoxazole | Amikacin Ampicillin Ampicillin-sulbactam Aztreonam Cefazolin Cefepime Ceftazidime Ceftazidime-avibactam Cefuroxime Ciprofloxacin Gentamicin Levofloxacin Meropenem Meropenem-vaborbactam Piperacillin-tazobactam Tigecycline Tobramycin Trimethoprim-sulfamethoxazole |
| Tested Organisms | *Acinetobacter* spp. (*Acinetobacter baumannii* complex) Enterobacterales (*Citrobacter freundii* complex, *Citrobacter koseri*, *Escherichia coli*, *Enterobacter cloacae* complex, *Klebsiella aerogenes*, *Klebsiella oxytoca*, | *Acinetobacter baumannii* *Citrobacter freundii*, *Citrobacter koseri*, *Escherichia coli*, *Enterobacter cloacae* complex, *Klebsiella aerogenes*, *Klebsiella* |

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| Device & Predicate Device(s): | K253573 (Device) | K221688 (Predicate) |
| --- | --- | --- |
| | Klebsiella pneumoniae group, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Serratia marcescens) Pseudomonas aeruginosa | oxytoca, Klebsiella pneumoniae, Proteus mirabilis, Proteus vulgaris, Serratia marcescens Pseudomonas aeruginosa |

### 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 breakpoint change protocol that was reviewed and accepted by FDA. This protocol 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 protocol outlined the specific procedures and acceptance criteria that Q-linea AB intends to use to evaluate the ASTar system with the ASTar BC G- Kit when revised breakpoints for indicated drugs are published on the FDA STIC webpage. The breakpoint change protocol included with the submission indicated that if specific criteria are met, Q-linea AB will update the ASTar BC GN- Kit label to include (1) the new breakpoints, (2) an updated performance section after re-evaluation of data in this premarket notification with the new breakpoints, and (3) any new limitations as determined by their evaluation.

### VI Standards/Guidance Documents Referenced:

- FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA (Issued August 28, 2009)
- CLSI M07, 12th Ed., 2024 Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically
- CLSI M100, 36th Ed., 2026 Performance Standards for Antimicrobial Susceptibility Testing
- AAMI TIR57:2016 (R2023) Principles for medical device security- Risk management
- CLSI AUTO11-A2, 2nd Ed., 2024 Information Technology Security of In Vitro Diagnostic Instruments and Software Systems
- CLSI EP07, 33rd Ed., 2021 Performance Standards for Antimicrobial Susceptibility Testing, R2022 Interference Testing in Clinical Chemistry
- CLSI EP25-A (Replaces EP25-P), 2023 Evaluation of Stability of In Vitro Diagnostic Reagents
- IEC 62304 Edition 1.1 2015-06 Consolidated Version, Medical device software - Software life cycle processes
- IEC 62366-1 Edition 1.1 2020-06 Consolidated Version, Medical devices - Part 1: Application of usability engineering to medical devices
- IEC 81001-5-1 Edition 1.0 2021-12 Health software and health IT systems safety, effectiveness and security - Part 5-1: Security - Activities in the product life cycle
- ISO 14971 Third Edition 2019-12 Medical devices - Application of risk management to medical devices
- ISO 15223-1 Fourth edition 2021-07 Medical devices - Symbols to be used with information to be supplied by the manufacturer - Part 1: General requirements

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- ISO 20417 First edition 2021-04 Corrected version 2021-12 Medical devices- Information to be supplied by the manufacturer

## VII Performance Characteristics (if/when applicable):

### A Analytical Performance:

#### 1. Precision/Reproducibility:

A reproducibility study with the ASTar System (ASTar BC G– Kit run on ASTar Instrument) was conducted using contrived positive blood culture bottles prepared with 27 bacterial strains from *Acinetobacter* spp. Enterobacterales, and *Pseudomonas aeruginosa*. Triplicate samples from each contrived blood culture were tested at three sites on at least two days. Reproducibility was determined from the total number (and percent) of results that were within one dilution (+/- one doubling dilution) of the modal MIC result divided by the total number of results. All samples were tested within 16 hours of bottle positivity. Both best-case (assumes that off-scale results are within one dilution of the mode) and worst-case (assumes that off-scale results are more than one dilution of the mode) performance was determined for each antimicrobial. Antimicrobials with an inter-site worst-case reproducibility of <89% or where an insufficient number of results were generated in the initial study were further evaluated in supplemental studies in which testing was conducted at one internal site with three individual instruments to increase the number of on-scale valid results. In general, testing was performed similar to the reproducibility study protocol used to support the original clearance of the ASTar System, as described in K221688. Overall, inter-site and intra-site reproducibility were >95% and determined to be acceptable. Reproducibility results for antimicrobials added to the ASTar BC G- Kit in the current submission are listed in **Table 1**.

**Table 1. Reproducibility of Antimicrobials Added to the ASTar BC G- Kit**

| Drug | Overall Best-case | Overall Worst-case |
| --- | --- | --- |
| Cefotaxime | 143/144 (99.3%) | 136/144 (94.4%) |
| Cefoxitin | 213/215 (99.1%) | 206/215 (95.8%) |
| Ceftolozane-tazobactam | 144/144 (100%) | 143/144 (99.3%) |
| Ceftriaxone | 125/125 (100%) | 116/125 (92.8%) |
| Ertapenem | 160/160 (100%) | 158/160 (98.8%) |

#### 2. Linearity:

Not Applicable

#### 3. Analytical Specificity/Interference:

##### Analytical Specificity

Not Applicable

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# Interference Studies

The potential impact of interfering substances on the results of the ASTar BC G- Kit with the ASTar system was previously assessed in K221688. Interference studies for the five new antimicrobials (cefotaxime, cefoxitin, ceftolozane-tazobactam, ceftriaxone, and ertapenem) added to the ASTar BC G- Kit in this submission were also performed following the study design described in the K221688 Decision Summary with the same interfering substances. Overall, the presence of high concentrations of the tested interferents in blood cultures does not interfere with the results of the new antimicrobials added to the ASTar BC G- Kit with the ASTar System.

# 4. Detection Limit and Assay Reportable Range:

Not Applicable

# 5. Traceability, Stability, Expected Values (Controls, Calibrators, or Methods):

Quality Control Testing. Quality control samples were run each day that testing was conducted. CLSI recommended QC strains for each antimicrobial were tested a sufficient number of times (i.e., at least 20 times/site) at each testing site using the ASTar System, including the reference site using the broth microdilution reference method. QC organisms were tested on a rotating basis. QC expected ranges and results for the ASTar System are summarized in Table 2. For all antimicrobials, greater than 95% of results were within the expected range, which is acceptable.

Table 2. QC Expected Ranges and Results for the Quantitative ASTar System

| Antimicrobial | ASTar QC Reportable Range (μg/mL) | QC Organism | CLSI Expected Range (μg/mL) | Number in Range (%) | |
| --- | --- | --- | --- | --- | --- |
| | | | | ASTar | Reference |
| Amikacin | ≤0.125 to ≥256 | E. coli ATCC 25922 | 0.5-4 | 63/63 (100%) | 46/46 (100%) |
| Ampicillin-sulbactam | ≤1 to ≥128 | E. coli ATCC 25922 | 2/1-8/4 | 61/63 (96.8%) | 41/41 (100%) |
| | | K. pneumoniae ATCC 700603 | 8/4-32/16 | 60/60 (100%) | 41/41 (100%) |
| Aztreonam | ≤0.125 to ≥128 | P. aeruginosa ATCC 27853 | 2-8 | 60/61 (98.4%) | 41/41 (100%) |
| Cefazolin | ≤0.125 to ≥32 | E. coli ATCC 25922 | 1-4 | 63/63 (100%) | 46/46 (100%) |
| Cefepime | ≤0.125 to ≥128 | P. aeruginosa ATCC 27853 | 0.5-4 | 61/61 (100%) | 41/41 (100%) |
| Cefotaxime | ≤0.008 to ≥256 | E. coli ATCC 25922 | 0.03-0.12 | 61/63 (96.8%) | 47/47 (100%) |
| Cefoxitin | ≤0.5 to ≥128 | E. coli ATCC 25922 | 2-8 | 63/63 (100%) | 46/46 (100%) |
| Ceftazidime | ≤0.25 to ≥128 | K. pneumoniae ATCC 700603^{a} | 16-64 | 60/60 (100%) | 46/47 (97.9%) |
| | ≤0.125 to ≥128 | P. aeruginosa ATCC 27853 | 1-4 | 60/61 (98.4%) | 45/47 (95.7%) |
| Ceftazidime-avibactam | ≤0.06 to ≥64 | K. pneumoniae ATCC 700603 | 0.25/4-2/4 | 60/60 (100%) | 46/47 (97.9%) |

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| Antimicrobial | ASTar QC Reportable Range (μg/mL) | QC Organism | CLSI Expected Range (μg/mL) | Number in Range (%) | |
| --- | --- | --- | --- | --- | --- |
| | | | | ASTar | Reference |
| | | *P. aeruginosa* ATCC 27853 | 0.5/4–4/4 | 60/60 (100%) | 47/47 (100%) |
| **Ceftolozane-tazobactam** | ≤0.06 to ≥64 | *K. pneumoniae* ATCC 700603 | 0.5/4–2/4 | 60/60 (100%) | 46/47 (97.9%) |
| | | *P. aeruginosa* ATCC 27853 | 0.25/4–1/4 | 60/61 (98.4%) | 47/47 (100%) |
| **Ceftriaxone** | ≤0.008 to ≥256 | *E. coli* ATCC 25922 | 0.03-0.12 | 61/63 (96.8%) | 44/47 (93.6%) |
| **Cefuroxime** | ≤0.5 to ≥128 | *E. coli* ATCC 25922 | 2-8 | 62/63 (98.4%) | 47/47 (100%) |
| **Ciprofloxacin** | ≤0.06 to ≥16 | *P. aeruginosa* ATCC 27853 | 0.12-1 | 61/61 (100%) | 46/46 (100%) |
| **Ertapenem** | ≤0.03 to ≥32 | *P. aeruginosa* ATCC 27853 | 2-8 | 60/60 (100%) | 42/46 (91.3%) |
| **Gentamicin** | ≤0.25 to ≥64 | *P. aeruginosa* ATCC 27853 | 0.5-2 | 61/61 (100%) | 46/46 (100%) |
| **Levofloxacin** | ≤0.125 to ≥32 | *P. aeruginosa* ATCC 27853 | 0.5-4 | 61/61 (100%) | 46/47 (97.9%) |
| **Meropenem** | ≤0.03 to ≥128 | *P. aeruginosa* ATCC 27853 | 0.12-1 | 61/61 (100%) | 40/40 (100%) |
| **Meropenem-vaborbactam** | ≤0.06 to ≥64 | *K. pneumoniae* ATCC BAA-2814 | 0.12/8–0.5/8 | 60/60 (100%) | 40/41 (97.6%) |
| | | *P. aeruginosa* ATCC 27853 | 0.12/8–1/8 | 60/61 (98.4%) | 41/41 (100%) |
| **Piperacillin-tazobactam** | ≤0.25 to ≥512 | *K. pneumoniae* ATCC 700603 | 8/4–32/4 | 60/60 (100%) | 46/47 (97.9) |
| | ≤0.125 to ≥512 | *P. aeruginosa* ATCC 27853 | 1/4–8/4 | 61/61 (100%) | 46/47 (97.9) |
| **Tobramycin** | ≤0.06 to ≥64 | *E. coli* ATCC 25922 | 0.25-1 | 63/63 (100%) | 46/46 (100%) |
| **Trimethoprim-sulfamethoxazole** | ≤0.03 to ≥16 | *E. coli* ATCC 25922 | ≤0.5/9.5 | 61/61 (100%) | 47/47 (100%) |

**Purity Check.** A purity check was performed on each positive blood culture sample to verify that only monomicrobial samples were included in the studies.

**Growth Failure Rate.** The growth failure rate for clinical samples with the ASTar system during the study was 4.1%.

### Microbial Suspension Accuracy Study

The microbial suspension accuracy of the ASTar System was previously assessed in K221688. Refer to the K221688 Decision Summary for additional details.

### Sample Stability Study

The sample stability of the ASTar BC G- Kit with the ASTar system was previously assessed in K221688. Sample stability studies for the five new antimicrobials (cefotaxime, cefoxitin, ceftolozane-tazobactam, ceftriaxone, and ertapenem) added to the ASTar BC G- Kit in this

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submission were also performed following the study design described in the K221688 Decision Summary. Overall, results for the new antimicrobials were acceptable for stability up to 16 hours (stored at both room temperature (RT) and at 35°C), consistent with the previous stability claims in K221688.

As noted in the instructions for use, all blood culture bottle samples should be tested immediately after a positive flag on a continuous monitoring system. In the case of unavoidable delays or if the need for re-testing arises, positive blood culture bottles may be tested up to 16 hours post ring.

6. Assay Cut-Off:

Not Applicable

7. Carry-Over:

The Carry-Over studies of the ASTar System was previously assessed in K221688. Refer to the K221688 Decision Summary for additional details.

# **B Comparison Studies:**

1. Method Comparison with Predicate Device:

Clinical performance testing with the ASTar System was performed at two external sites and one internal site. The broth microdilution reference method testing was performed at a single reference site. Performance was evaluated using fresh (prospective) positive blood cultures, as well as positive blood culture samples seeded with clinical stock isolates and challenge isolates. Organism identification was obtained from an FDA cleared molecular bacterial identification method and/or FDA cleared MALDI TOF method for input into the ASTar system. The species identification provided by the clinical site was confirmed at the reference site using an FDA-cleared MALDI identification method. For any samples with a species identification at the reference site not matching the expected ID or found to be polymicrobial, the sample was excluded from the final performance data according to the exclusion criteria.

Performance testing of the ASTar system included five (5) new antimicrobials added to the ASTar BC G- Kit (cefotaxime, cefoxitin, ceftolozane-tazobactam, ceftriaxone, and ertapenem), as well as additional organisms tested with antimicrobials cleared in K221688. A total of 598 positive blood cultures (167 fresh (prospective), 221 seeded with clinical stock organisms, and 210 seeded with challenge organisms) with new antimicrobials were tested to evaluate the ASTar System performance. A total of 630 positive blood culture bottles (167 fresh (prospective), 221 seeded with clinical stock organisms, and 242 seeded with challenge organisms) with cleared antimicrobials were tested to evaluate the ASTar system performance. Additionally, clinical data for some antimicrobials cleared in K221688 were reanalyzed to evaluate performance of the ASTar system and ASTar BC G- Kit with updated FDA STIC breakpoints.

ASTar system results were compared to results obtained with the CLSI broth microdilution (BMD) reference method. Reference BMD panels were run in triplicate for each isolate and an MIC mode was determined for comparison with the ASTar BC G- Kit MIC result. If an

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MIC mode could not be established from the first three BMD results, a second set of BMD assays was run in triplicate and the MIC mode across all six tests was determined. If a mode still could not be established, the median MIC was used for comparison with the ASTar BC G- Kit MIC result.

Performance was determined generally based on criteria outlined in the Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems including essential agreement (EA), category agreement (CA), and categorical errors (minor, major and very major errors). EA was calculated as the percentage of ASTar MIC results that were within ± 1 serial two-fold dilution of the reference result. CA was calculated as the percentage of ASTar interpretive results (S/I/SDD/R) that were identical to the interpretive results of the reference result. EA of evaluable results (on-scale ASTar and reference results or results in which an off-scale result was at least two doubling dilutions from the on-scale result) were also calculated. Performance was considered acceptable if the EA and CA were ≥89.9%, major error rate was ≤3%, and very major error rate was ≤2%. For antimicrobials that lack an intermediate interpretive result, further analysis of the category errors was performed, and adjustments were made by considering the MIC values that were one doubling dilution from the reference MIC value. For antimicrobial/organism group combinations in this submission where the susceptible-dose dependent category is recognized in place of the intermediate category (S/I/SDD/R), any errors that were observed with this category were designated as minor errors.

A summary of the performance of the ASTar System is described below for each antimicrobial/organism combinations as follows, and the data is summarized in the corresponding indicted tables:

A. ASTar Performance with New Antimicrobials (Table 3).
B. Acceptable ASTar Performance of Additional Organisms with Previously Cleared Antimicrobials (Table 4) and Unacceptable ASTar Performance of Additional Organisms with Previously Cleared Antimicrobials (Table 5).
C. Additional Testing to Remove Performance Limitations with Cleared Antimicrobials (Table 6).
D. ASTar Performance of Antimicrobials with Updated Breakpoints (Table 7).

### A. ASTar Performance with New Antimicrobials

Data for several of the antimicrobials included in this submission was previously submitted and reviewed in K221688. Claims were not granted due to unacceptable performance; refer to K221688 Decision Summary. In this submission, additional testing was performed to support the addition of these antimicrobials to the ASTar BC G- Kit. The performance data for these antimicrobial/organism combinations is provided in Table 3.

Cefotaxime/Enterobacterales. A total of 478 Enterobacterales (19 C. freundii complex, 22 C. koseri, 25. E. cloacae complex, 131 E. coli, 19 K. aerogenes, 54 K. oxytoca, 99 K. pneumoniae group, 26 M. morganii, 37 P. mirabilis, 15 P. vulgaris, and 31 S. marcescens) were evaluated. The combined results from the clinical and challenge testing demonstrated an EA of 95.6% and CA of 96.7%. There were eight (8) minor errors, seven (7) major errors

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(7/321 = 2.1%), and one (1) very major error (1/150 = 0.7%). Overall performance is acceptable.

When evaluating by individual species, E. coli had one (1) very major error (1/34 = 2.9%), which is not acceptable. A limitation is included in the device labeling to address the unacceptable very major error rate by restricting reporting at an ASTar MIC of 1 μg/mL. K. aerogenes demonstrated an EA of 84.2%, which is not acceptable. Due to the unacceptable EA, this antimicrobial/organism combination is not indicated for use with the ASTar system. M. morganii demonstrated an EA of 69.2% and a CA of 73.1%, which is not acceptable. There were two (2) minor errors, five (5) major errors (5/18 = 27.8%), and no very major errors. Due to the unacceptable EA, CA, and major error rate of M. morganii, this antimicrobial/organism combination is not indicated for use with the ASTar system. The following limitation is included in the device labeling to address the very major error rate of E. coli, the unacceptable EA performance of K. aerogenes, and the unacceptable EA, CA, and major error rate of M. morganii:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Cefotaxime: Escherichia coli when the ASTar MIC is 1 μg/mL due to one very major discrepancy, Klebsiella aerogenes, Morganella morganii

A limitation statement is included in the device labeling to address the lack of testing with resistant Citrobacter freundii complex and Proteus vulgaris isolates.

Based on the performance described above, the following limitation was removed from device labeling:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Cefotaxime: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae group, Proteus mirabilis, Proteus vulgaris, Serratia marcescens

Cefoxitin/Enterobacterales. A total of 375 Enterobacterales (22 C. koseri, 131 E. coli, 42 K. oxytoca, 99 K. pneumoniae group, 27 M. morganii, 37 P. mirabilis, and 17 P. vulgaris) were evaluated. The combined results from the clinical and challenge testing demonstrated an EA of 96.8% and CA of 89.1%. The <90% CA was considered acceptable since the majority of the categorical errors were minor and the EA of evaluable results was high. There were 38 minor errors, one (1) major error (1/248 = 0.4%), and two (2) very major errors (2/83 = 2.4%).

When evaluating by individual species, E. coli demonstrated an EA of 97.0% and a CA of 87.0%. There were 17 minor errors, no major errors, and no very major errors. The <90% CA was considered acceptable since all of the categorical errors were minor and the EA of evaluable results was high. K. oxytoca had one (1) very major error (1/14 = 7.1%), which is not acceptable. A limitation is included in the device labeling to address the unacceptable very major error rate by restricting reporting at an ASTar MIC of 4 μg/mL. M. morganii demonstrated an EA of 96.3% and a CA of 63.0%, which is not acceptable. There were 10

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minor errors, no major errors, and no very major errors. Due to the unacceptable CA of M. morganii, this antimicrobial/organism combination is not indicated for use with the ASTar System. P. mirabilis had one very major error (1/5 = 20%). This very major error is considered a random error due to the limited number of resistant isolates tested, and the performance is acceptable. P. vulgaris demonstrated an EA of 88.2% and a CA of 76.5%, which is not acceptable. There were three (3) minor errors, one (1) major error (1/13 = 7.7%), and no very major errors. Due to the unacceptable EA, CA, and major error rate of P. vulgaris, this antimicrobial/organism combination is not indicated for use with the ASTar System. The following limitation is included in the device labeling to address the very major error rate of K. oxytoca and the unacceptable EA, CA and major error rate of P. vulgaris:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Cefoxitin: Klebsiella oxytoca when the ASTar MIC is 4 μg/mL due to one very major discrepancy, Morganella morganii, Proteus vulgaris

Ceftolozane-tazobactam/Enterobacterales. A total of 473 Enterobacterales (19 C. freundii complex, 22 C. koseri, 25 E. cloacae complex, 131 E. coli, 21 K. aerogenes, 43 K. oxytoca, 98 K. pneumoniae group, 27 M. morganii, 37 P. mirabilis, 17 P. vulgaris, and 33 S. marcescens) were evaluated. The combined results from the clinical and challenge testing demonstrated an EA of 96.8% and CA of 97.3%. There were 11 minor errors, one (1) major error (1/390 = 0.3%), and one (1) very major error (1/78 = 1.3%). Overall performance is acceptable.

When evaluating by individual species, K. aerogenes demonstrated an EA of 90.5% and a CA of 81.0%, which is not acceptable. There were three (3) minor errors, no major errors, and one (1) very major error (1/3 = 33.3%). Due to the unacceptable CA and very major error rate of K. aerogenes, this antimicrobial/organism combination is not indicated for use with the ASTar System. M. morganii had one (1) major error (1/24 = 4.2%), which is not acceptable. Due to the unacceptable major error rate of M. morganii, this antimicrobial/organism combination is not indicated for use with the ASTar System. The following limitation is included in the device labeling to address the unacceptable CA and very major error rate of K. aerogenes and the unacceptable major error rate of M. morganii:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Ceftolozane-tazobactam: Klebsiella aerogenes, Morganella morganii

A limitation statement is included in the device labeling to address the lack of testing with resistant Citrobacter freundii complex, Proteus vulgaris, and Serratia marcescens isolates.

Ceftolozane-tazobactam/P. aeruginosa. A total of 60 P. aeruginosa were evaluated. The combined results from the clinical and challenge testing demonstrated an EA of 93.3% and CA of 93.3%. There were four (4) minor errors, no major error, and no very major errors. Overall performance is acceptable.

Based on the performance described for both Enterobacterales and P. aeruginosa above, the following limitation was removed from device labeling:

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Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Ceftolozane-tazobactam: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae group, Proteus mirabilis, Proteus vulgaris, Serratia marcescens, Pseudomonas aeruginosa

Ceftriaxone/Enterobacterales. A total of 480 Enterobacterales (19 C. freundii complex, 22 C. koseri, 24 E. cloacae complex, 131 E. coli, 20 K. aerogenes, 54 K. oxytoca, 98 K. pneumoniae group, 26 M. morganii, 37 P. mirabilis, 16 P. vulgaris, and 33 S. marcescens) were evaluated. The combined results from the clinical and challenge testing demonstrated an EA of 97.1% and CA of 98.3%. There were five (5) minor errors, three (3) major error (3/326 = 0.9%), and no very major errors. Overall performance is acceptable.

When evaluating by individual species, M. morganii demonstrated an EA of 80.8% a CA of 84.6%, which is not acceptable. There were three (3) minor errors, one (1) major error (1/18 = 5.6%), and no very major errors. Due to the unacceptable EA, CA, and major error rate of M. morganii, this antimicrobial/organism combination is not indicated for use with the ASTar System. P. vulgaris had one (1) major error (1/15 = 6.7%), which is not acceptable. A limitation is included in the device labeling to address the unacceptable very major error rate by restricting reporting at an ASTar MIC of 4 μg/mL. The following limitation is included in the device labeling to address the unacceptable EA, CA and major error rate of M. morganii and the unacceptable major error rate of P. vulgaris:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Ceftriaxone: Proteus vulgaris when the ASTar MIC is 4 μg/mL due to one very major discrepancy, Morganella morganii

Based on the performance described above, the following limitation was removed from device labeling:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Ceftriaxone: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumoniae group, Proteus mirabilis, Serratia marcescens

A limitation statement is included in the device labeling to address the lack of testing with resistant Citrobacter freundii complex and Proteus vulgaris isolates.

Ertapenem/Enterobacterales. A total of 477 Enterobacterales (19 C. freundii complex, 22 C. koseri, 25 E. cloacae complex, 131 E. coli, 21 K. aerogenes, 43 K. oxytoca, 99 K. pneumoniae group, 27 M. morganii, 40 P. mirabilis, 17 P. vulgaris, and 33 S. marcescens) were evaluated. The combined results from the clinical and challenge testing demonstrated an EA of 95.2% and CA of 97.9%. There were six (6) minor errors, two (2) major error (2/393 = 0.5%), and two (2) very major errors (2/6 = 33.3%).

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When evaluating by individual species, K. aerogenes demonstrated an EA of 81.0%, a CA of 81%, which is not acceptable. There were four (4) minor errors, no major errors, and no major errors. Due to the unacceptable EA and CA of K. aerogenes, this antimicrobial/organism combination is not indicated for use with the ASTar System. K. pneumoniae group had one (1) very major error (1/36 = 2.8%), which is not acceptable. A limitation is included in the device labeling to address the unacceptable very major error rate by restricting reporting at an ASTar MIC of 0.5 μg/mL. M. morganii demonstrated an EA of 88.9% and had one (1) major error (1/25 = 4.0%), which is not acceptable. Due to do the unacceptable EA and major error rate of M. morganii, this antimicrobial/organism combination is not indicated for use with the ASTar System. P. mirabilis had one (1) very major error (1/1 = 100%). This very major error is considered a random error due to the limited number of resistant isolates tested, and the performance is acceptable. The following limitation is included in the device labeling to address the unacceptable EA and CA of K. aerogenes, the very major error rate of K. pneumoniae group, the unacceptable EA and major error rate of M. morganii:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Ertapenem: Klebsiella aerogenes, Klebsiella pneumoniae group when the ASTar MIC is 0.5 μg/mL due to one very major discrepancy, Morganella morganii

A limitation statement is included in the device labeling to address the lack of testing with resistant Citrobacter freundii complex, Proteus mirabilis, Proteus vulgaris, and Proteus vulgaris isolates.

Based on the performance described above, the following limitation was removed from device labeling:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Ertapenem: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae complex, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae group, Proteus mirabilis, Proteus vulgaris, Serratia marcescens

Table 3. ASTar Performance with New Antimicrobials

| | Tot | No. EA | EA % | Eval EA Tot | No. Eval EA | Eval EA % | No. CA | CA % | No. R | No. S | min | maj | vmj |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| **Cefotaxime: Enterobacterales [≤1 (S), 2 (I), ≥4 (R)]** | | | | | | | | | | | | | |
| Challenge | 157 | 152 | 96.8 | 14 | 9 | 64.3 | 154 | 98.1 | 39 | 116 | 3 | 0 | 0 |
| Fresh | 153 | 148 | 96.7 | 8 | 3 | 37.5 | 150 | 98.0 | 36 | 117 | 0 | 2 | 1 |
| Seeded Clinical | 168 | 157 | 93.5 | 30 | 19 | 63.3 | 158 | 94.1 | 75 | 88 | 5 | 5 | 0 |
| Combined | 478 | 457 | 95.6 | 52 | 31 | 59.6 | 462 | 96.7 | 150 | 321 | 8 | 7 | 1 |
| **Cefoxitin: Enterobacterales [≤4 (S), 8 (I), ≥16 (R)]** | | | | | | | | | | | | | |
| Challenge | 87 | 87 | 100 | 64 | 64 | 100 | 84 | 96.6 | 27 | 56 | 3 | 0 | 0 |
| Fresh | 141 | 133 | 94.3 | 126 | 118 | 93.7 | 120 | 85.1 | 11 | 122 | 20 | 1 | 0 |

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| | Tot | No. EA | EA % | Eval EA Tot | No. Eval EA | Eval EA % | No. CA | CA % | No. R | No. S | min | maj | vmj |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Seeded Clinical | 147 | 143 | 97.3 | 118 | 114 | 96.6 | 130 | 88.4 | 45 | 70 | 15 | 0 | 2 |
| Combined | 375 | 363 | 96.8 | 308 | 296 | 96.1 | 334 | 89.1 | 83 | 248 | 38 | 1 | 2 |
| **Ceftolozane-tazobactam: Enterobacterales [≤2/4 (S), 4/4 (I), ≥8/4 (R)]** | | | | | | | | | | | | | |
| Challenge | 149 | 147 | 98.7 | 33 | 31 | 93.9 | 145 | 97.3 | 31 | 116 | 1 | 0 | 0 |
| Fresh | 153 | 149 | 97.4 | 19 | 15 | 79.0 | 151 | 98.7 | 5 | 147 | 1 | 0 | 1 |
| Seeded Clinical | 171 | 162 | 97.4 | 61 | 52 | 85.3 | 164 | 95.9 | 42 | 127 | 6 | 1 | 0 |
| Combined | 473 | 458 | 96.8 | 113 | 98 | 86.7 | 460 | 97.3 | 78 | 390 | 11 | 1 | 1 |
| **Ceftolozane-tazobactam: Pseudomonas aeruginosa [≤4/4 (S), 8/4 (I), ≥16/4 (R)]** | | | | | | | | | | | | | |
| Challenge | 24 | 23 | 95.8 | 20 | 19 | 95.0 | 24 | 100 | 3 | 21 | 0 | 0 | 0 |
| Fresh | 12 | 12 | 100 | 12 | 12 | 100 | 12 | 100 | 0 | 12 | 0 | 0 | 0 |
| Seeded Clinical | 24 | 21 | 87.5 | 24 | 21 | 87.5 | 20 | 83.3 | 1 | 19 | 4 | 0 | 0 |
| Combined | 60 | 56 | 93.3 | 56 | 52 | 92.9 | 56 | 93.3 | 4 | 52 | 4 | 0 | 0 |
| **Ceftriaxone: Enterobacterales [≤1 (S), 2 (I), ≥4 (R)]** | | | | | | | | | | | | | |
| Challenge | 158 | 156 | 98.7 | 10 | 8 | 80.0 | 157 | 99.4 | 40 | 118 | 1 | 0 | 0 |
| Fresh | 152 | 148 | 97.4 | 8 | 4 | 50.0 | 150 | 98.7 | 34 | 117 | 1 | 1 | 0 |
| Seeded Clinical | 170 | 162 | 95.3 | 22 | 14 | 63.6 | 165 | 97.1 | 71 | 91 | 3 | 2 | 0 |
| Combined | 480 | 466 | 97.1 | 40 | 26 | 65.0 | 472 | 98.3 | 145 | 326 | 5 | 3 | 0 |
| **Ertapenem: Enterobacterales [≤0.5 (S), 1 (I), ≥2 (R)]** | | | | | | | | | | | | | |
| Challenge | 152 | 146 | 96.1 | 20 | 14 | 70.0 | 148 | 97.4 | 31 | 116 | 4 | 0 | 0 |
| Fresh | 153 | 149 | 97.4 | 10 | 6 | 60.0 | 151 | 98.7 | 4 | 147 | 2 | 0 | 0 |
| Seeded Clinical | 172 | 159 | 92.4 | 32 | 19 | 59.4 | 168 | 97.7 | 38 | 133 | 0 | 2 | 2 |
| Combined | 477 | 454 | 95.2 | 62 | 39 | 62.9 | 467 | 97.9 | 73 | 396 | 6 | 2 | 2 |

EA – Essential Agreement
CA – Category Agreement
R – Resistant
S – Susceptible

Eval – Evaluable MIC Results
min – Minor Discrepancies
maj – Major Discrepancies
vmj – Very Major Discrepancies

Essential Agreement (EA) occurs when there is agreement between the reference method and ASTar MIC results within plus or minus one serial two-fold dilution of the antibiotic. Evaluable results are those that are on-scale for both the ASTar and the reference method or those in which an off-scale result is at least two doubling dilutions from the on-scale result. Category Agreement (CA) occurs when the interpretation of the reference method and ASTar result are in exact agreement.

### B. Acceptable ASTar Performance of Additional Organisms with Previously Cleared Antimicrobials

For some antimicrobials originally cleared in K221688, performance of additional organisms was evaluated. Antimicrobial/organism combinations for which performance was acceptable are provided in Table 4 and antimicrobial/organism combinations for which performance was unacceptable are provided in Table 5.

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# Amikacin

A total of 50 A. baumannii complex were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 96.0% and CA of 98.0%. There was one (1) minor error, no major errors, and no very major errors. Performance is acceptable.

A total of 22 C. koseri were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 95.5% and CA of 95.5%. There was one (1) minor error and no major or very major errors. Performance is acceptable.

A total of 131 E. coli were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 98.5% and CA of 99.2%. There was one (1) minor error and no major or very major errors. Performance is acceptable.

A total of 27 M. morganii were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 96.3% and CA of 96.3%. There was one (1) minor error and no major or very major errors. Performance is acceptable.

A total of 16 P. vulgaris were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 100%. There were no minor errors, no major errors, and very major errors. Performance is acceptable.

A limitation statement is included in the device labeling to address the lack of testing with resistant Citrobcter koseri, Morganella morganii, and Proteus vulgaris isolates.

Based on the performance described above, the following limitation was removed from device labeling:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Amikacin: Acinetobacter baumannii complex, Escherichia coli, Proteus vulgaris

# Ampicillin-sulbactam

A total of 50 A. baumannii complex were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 96.0% and CA of 90.0%. There were five (5) minor errors, no major errors, and no very major errors. Performance is acceptable

A total of 22 C. koseri were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 27 M. morganii were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 96.3% and CA of 85.2%. There were four (4) minor errors, no major errors, and no very major errors. The <90% CA was considered acceptable since all of the categorical errors were minor and the EA of evaluable results was high. Performance is acceptable.

Based on the performance described above, the following limitation was removed from device labeling:

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Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Ampicillin-sulbactam: Acinetobacter baumannii complex

### Aztreonam

A total of 19 C. freundii complex were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 26 M. morganii were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 96.2% and CA of 96.2%. There was one (1) minor error, no major errors, and no very major errors. Performance is acceptable.

A total of 83 P. aeruginosa were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 91.7% and CA of 81.9%. There were fifteen (15) minor errors, no major errors, and no very major errors. The <90% CA was considered acceptable since all of the categorical errors were minor and the EA of evaluable results was high. Performance is acceptable.

A limitation statement is included in the device labeling to address the lack of testing with resistant Citrobcter freundii complex isolates.

Based on the performance described above, the following limitation was removed from device labeling:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Aztreonam: Citrobacter freundii complex, Pseudomonas aeruginosa

### Cefazolin

A total of 22 C. koseri were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 95.5%. There was one (1) minor error, no major errors, and no very major errors. Performance is acceptable.

A total of 131 E. coli were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 97.7% and CA of 93.1%. There were nine (9) minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 43 K. oxytoca were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 97.7% and CA of 88.4%. There were four (4) minor errors, one (1) major error (1/5 = 20%), and no very major errors. The <90% CA was considered acceptable since the majority of the categorical errors were minor and the EA of evaluable results was high. The major error is considered a random error due to the limited number of susceptible isolates tested. Performance is acceptable.

A total of 37 P. mirabilis were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 97.3% and CA of 86.5%. There were five (5) minor

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errors, no major errors, and no very major errors. The <90% CA was considered acceptable since all of the categorical errors were minor and the EA of evaluable results was high. Performance is acceptable.

Based on the performance described above, the following limitation was removed from device labeling:

*Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):*

- *Cefazolin: Citrobacter koseri, Escherichia coli, Klebsiella oxytoca, Proteus mirabilis*

### **Cefepime**

A total of 22 *C. koseri* were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 95.5% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 25 *E. cloacae* complex were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 92.0% and CA of 96.0%. There was one (1) minor error, no major errors, and no very major errors. Performance is acceptable.

A total of 27 *M. morganii* were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 88.9% and CA of 92.6%. There were no minor errors, one (1) major error ($1/24 = 4.2\%$), and one (1) very major error ($1/3 = 33.3\%$). Due to the unacceptable EA, major error rate, and very major error rate of *M. morganii*, this antimicrobial/ organism combination is not indicated for use with the ASTar System, and the following limitation is included in the device labeling:

*Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):*

- *Cefepime: Morganella morganii*

A limitation statement is included in the device labeling to address the lack of testing with resistant *Proteus vulgaris* isolates.

Based on the performance described above, the following limitations were removed from device labeling:

*The ability of the ASTar system to detect resistance in the following antimicrobial/ organism combinations is unknown because of an insufficient number of resistant isolates were available during the clinical study:*

- *Cefepime: Citrobacter koseri*

*Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):*

- *Cefepime: Enterobacter cloacae complex*

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# Ceftazidime

A total of 50 A. baumannii complex were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 98.0% and CA of 92.0%. There were four (4) minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 19 C. freundii complex were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 22 C. koseri were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 21 K. aerogenes were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 90.5% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 26 M. morganii were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 96.2% and CA of 92.3%. There was one (1) minor error, one (1) major error (1/18 = 5.6%), and no very major errors. The following limitation is included in the device labeling to address the unacceptable major error rate:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Ceftazidime: Morganella morganii when the ASTar MIC is 64 μg/mL due to one major discrepancy

A total of 60 P. aeruginosa were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 90.0% and CA of 95.0%. There were two (2) minor errors, no major errors, and one (1) very major error (1/14 = 7.1%). Due to the unacceptable very major error rate, this antimicrobial/ organism combination is not indicated for use with the ASTar System, and the following limitation is included in the device labeling:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Ceftazidime: Pseudomonas aeruginosa

A limitation statement is included in the device labeling to address the lack of testing with resistant Citrobacter freundii complex isolates.

Based on the performance described above, the following limitation was removed from device labeling:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Ceftazidime: Acinetobacter baumannii complex, Citrobacter freundii complex, Citrobacter koseri, Klebsiella aerogenes

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### Ceftazidime-avibactam

A total of 131 *E. coli* were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 98.5% and CA of 99.2%. There were no minor errors, one (1) major error ($1/125 = 0.8\%$), and no very major errors. Due to the lack of an intermediate breakpoint, further analysis of the errors was performed, and adjustments were made by considering the MIC values of the errors compared to the reference MIC values. The one major error is not in essential agreement with the reference MIC values; and the adjusted major error rate is 0.8% ($1/125$). Performance is acceptable.

A total of 21 *K. aerogenes* were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 97 *K. pneumoniae* group were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 96.9% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 27 *M. morganii* were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 17 *P. vulgaris* were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A limitation statement is included in the device labeling to address the lack of testing with resistant *Klebsiella aerogenes*, *Morganella morganii*, and *Proteus vulgaris* isolates.

Based on the performance described above, the following limitation was removed from device labeling:

*Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):*

- *Ceftazidime-avibactam*: *Escherichia coli*, *Klebsiella aerogenes*, *Klebsiella pneumoniae* group

### Cefuroxime

A total of 22 *C. koseri* were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 95.5% and CA of 95.5%. There were no minor errors, no major errors, and one (1) very major error ($1/8 = 12.5\%$). Due to the lack of an intermediate breakpoint, further analysis of the errors was performed, and adjustments were made by considering the MIC values of the errors compared to the reference MIC values. The one very major error is in essential agreement with the reference MIC values. Therefore, the very major error rate was adjusted to 0% ($0/8$). Performance is acceptable.

A total of 25 *E. cloacae* complex were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 92.0% and CA of 88.0%, which is not acceptable. There were no minor errors, no major errors, and three (3) very major errors

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(3/14 = 21.4%). Due to the lack of an intermediate breakpoint, further analysis of the errors was performed, and adjustments were made by considering the MIC values of the errors compared to the reference MIC values. Two of the three very major errors were in essential agreement with the reference MIC values. Therefore, the very major error rate was adjusted to 7.1% (1/14), which is still not acceptable. Due to the unacceptable CA and very major error rate of *E. cloacae* complex, this antimicrobial/ organism combination is not indicated for use with the ASTar System, and the limitation below is included in the device labeling.

A total of 20 *K. aerogenes* were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 80.0% and CA of 85.0%, which is not acceptable. There were no minor errors, no major errors, and three (3) very major errors (3/9 = 33.3%). Due to the lack of an intermediate breakpoint, further analysis of the errors was performed, and adjustments were made by considering the MIC values of the errors compared to the reference MIC values. One of the three very major errors was in essential agreement with the reference MIC values. Therefore, the very major error rate was adjusted to 22.2% (2/9), which is still not acceptable. Due to the unacceptable EA, CA, and very major error rate of *K. aerogenes*, this antimicrobial/ organism combination is not indicated for use with the ASTar System, and the following limitation is included in the device labeling:

*Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):*

- *Cefuroxime: Enterobacter cloacae complex, Klebsiella aerogenes*

Based on the performance described above, the following limitation was removed from device labeling:

*Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):*

- *Cefuroxime: Citrobacter koseri*

### **Ciprofloxacin**

A total of 19 *C. freundii* complex were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 100%. There were no minor errors, no major errors, and no very major errors. Performance is acceptable.

A total of 27 *M. morganii* were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of 100%. There was one (1) minor error, no major errors, and no very major errors. Performance is acceptable.

A limitation statement is included in the device labeling to address the lack of testing with resistant *Citrobacter freundii* complex isolates.

Based on the performance described above, the following limitation was removed from device labeling:

*Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):*

- *Ciprofloxacin: Citrobacter freundii complex*

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# Gentamicin

A total of 25 E. cloacae complex were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 72.0% and CA of 96.0%, which is not acceptable. There was one (1) minor error, no major errors, and no very major errors. Due to the unacceptable EA, this antimicrobial/ organism combination is not indicated for use with the ASTar System, and the limitation below is included in the device labeling.

A total of 131 E. coli were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 87.8% and CA of 99.2%, which is not acceptable. There was one (1) minor error, no major errors, and no very major errors. Due to the unacceptable EA, this antimicrobial/ organism combination is not indicated for use with the ASTar System, and the limitation below is included in the device labeling.

A total of 21 K. aerogenes were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 85.7% and CA of 100%, which is not acceptable. There were no minor errors, no major errors, and no very major errors. Due to the unacceptable EA, this antimicrobial/ organism combination is not indicated for use with the ASTar System, and the following limitation is included in the device labeling:

Perform an alternative method of testing prior to reporting results for the following antibiotic/organism combination(s):

- Gentamicin: Enterobacter cloacae complex, Escherichia coli, Klebsiella aerogenes

A total of 26 M. morganii were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 96.2% and CA of 84.6%. There were three (3) minor errors, no major errors, and one (1) very major error (1/8 = 12.5%). The <90% CA was considered acceptable since the majority of the categorical errors were minor and the EA of evaluable results was high. The very major error is considered a random error due to the limited number of resistant isolates tested. Performance is acceptable.

A limitation statement is included in the device labeling to address the lack of testing with resistant Morganella morganii isolates.

# Levofloxacin

A total of 27 M. morganii were evaluated, and the combined results from the clinical and challenge testing demonstrated an EA of 100% and CA of…