MicroScan Dried Gram Negative MIC/Combo Panels with Ceftazidime/Avibactam (0.25/4 - 64/4 ug/mL)

K172337 · Beckman Coulter, Inc. · LTT · Dec 15, 2017 · Microbiology

Device Facts

• Record ID: K172337
• Device Name: MicroScan Dried Gram Negative MIC/Combo Panels with Ceftazidime/Avibactam (0.25/4 - 64/4 ug/mL)
• Applicant: Beckman Coulter, Inc.
• Product Code: LTT · Microbiology
• Decision Date: Dec 15, 2017
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 866.1640
• Device Class: Class 2

Indications for Use

The MicroScan Dried Gram-Negative MIC/Combo Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of rapidly growing aerobic and facultative anaerobic gram-negative bacilli. After inoculation, panels are incubated for 16 - 20 hours at 35°C +/ - 1°C in a non-CO2 incubator, and read either visually or with MicroScan instrumentation, according to the Package Insert. This particular submission is for the antimicrobial ceftazidime/avibactam at concentrations of 0.25/4 to 64/4 ug/mL to the test panel. The gram-negative organisms which may be used for ceftazidime/avibactam susceptibility testing in this panel are: Citrobacter freundii complex, Citrobacter koseri, Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca. Klebsiella pneumoniae, Morganii, Proteus mirabilis. Pseudomonas aeruginosa. Providencia rettgeri, Providencia stuartii, and Serratia marcescens

Device Story

MicroScan Dried Gram-Negative MIC/Combo Panels determine antimicrobial susceptibility of gram-negative bacilli. Device uses dehydrated miniaturized broth microdilution; Mueller Hinton broth supplemented with calcium/magnesium. Inoculation via turbidity or Prompt Inoculation System; incubation 16–20 hours at 35°C. Read methods include manual visual inspection or automated MicroScan WalkAway/autoSCAN-4 instruments. Output is Minimum Inhibitory Concentration (MIC) and categorical interpretation (SIR). Used in clinical microbiology laboratories to guide antibiotic therapy for gram-negative infections. Provides quantitative susceptibility data to assist clinicians in selecting appropriate antimicrobial treatment.

Clinical Evidence

Bench-only study. Evaluated 539 clinical and 87 challenge Enterobacteriaceae isolates, plus 79 clinical and 29 challenge P. aeruginosa isolates. Compared MicroScan panels (Prompt/Turbidity inoculation; Manual/WalkAway/autoSCAN-4 read) against frozen broth microdilution reference. Overall essential agreement (EA) and category agreement (CA) were ≥90%. Adjusted very major error rates were 0% for Enterobacteriaceae and 7.7% for P. aeruginosa. Limitations noted for P. rettgeri, S. marcescens, P. stuartii, and P. aeruginosa due to error rates or lack of resistant strains.

Technological Characteristics

Miniaturized broth microdilution panels; dehydrated antimicrobial agents in wells. Rehydrated with water. Incubation: 16-20 hours at 35°C. Compatible with visual reading or automated instrumentation (autoSCAN-4, WalkAway).

Indications for Use

Indicated for determining quantitative and/or qualitative antimicrobial susceptibility of colonies grown on solid media of rapidly growing aerobic and facultative anaerobic gram-negative bacilli, specifically: Citrobacter freundii complex, Citrobacter koseri, Enterobacter aerogenes, Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Proteus mirabilis, Pseudomonas aeruginosa, Providencia rettgeri, Providencia stuartii, and Serratia marcescens.

Regulatory Classification

Identification

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

Predicate Devices

• MicroScan Dried Gram-Negative MIC/Combo Panels - Imipenem (K162740)

Submission Summary (Full Text)

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# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY ASSAY ONLY TEMPLATE

A. 510(k) Number:
K172337

B. Purpose for Submission:
To obtain a substantial equivalence determination for the addition of Ceftazidime/Avibactam to the MicroScan Dried Gram-Negative MIC/Combo Panels with Ceftazidime/Avibactam (0.25/4 – 64/4 µg/mL).

C. Measurand:
Ceftazidime/Avibactam in the dilution range of 0.25/4 – 64/4 µg/mL. The avibactam concentration is fixed at 4 µg/mL in this combination.

D. Type of Test:
Quantitative Antimicrobial Susceptibility Test (AST)

E. Applicant:
Beckman Coulter

F. Proprietary and Established Names:
MicroScan Dried Gram-Negative MIC/Combo Panels with Ceftazidime/Avibactam (0.25/4 – 64/4 µg/mL)

G. Regulatory Information:
1. Regulation section:
21 CFR 866.1640 Antimicrobial Susceptibility Test Powder
2. Classification:
Class II
3. Product codes:
LTT – Panels, Test, Susceptibility, Antimicrobial
JWY – Manual Antimicrobial Susceptibility Test Systems

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LRG – Instrument for Auto Reader and Interpretation of Overnight Susceptibility Systems

LTW – Susceptibility Test Cards, Antimicrobial

4. Panel:

83 - Microbiology

H. Intended Use:

1. Intended use(s):

For use with MicroScan Dried Gram Negative MIC/Combo Panels and Dried Gram Negative Breakpoint Combo panels. MicroScan panels are designed for use in determining antimicrobial agent susceptibility and/or identification to the species level of aerobic and facultatively anaerobic gram-negative bacilli.

2. Indication(s) for use:

The MicroScan Dried Gram-Negative MIC/Combo Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of rapidly growing aerobic and facultative anaerobic gram-negative bacilli. After inoculation, panels are incubated for 16 – 20 hours at 35°C ± 1°C in a non-CO₂ incubator, and read either visually or with MicroScan instrumentation, according to the package insert.

This particular submission is for the addition of the antimicrobial ceftazidime/avibactam at concentrations of 0.25/4 to 64/4 µg/mL to the test panel.

The gram-negative organisms which may be used for ceftazidime/avibactam susceptibility testing in this panel are:

Citrobacter freundii complex, Citrobacter koseri, Enterobacter aerogenes, Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Proteus mirabilis, Pseudomonas aeruginosa, Providencia rettgeri, Providencia stuartii and Serratia marcescens.

3. Special conditions for use statement(s):

For Prescription use only.

Limitations:

Results obtained with P. rettgeri and ceftazidime/avibactam with the Prompt Inoculation system and WalkAway read were outside of essential agreement compared to the reference method; results should be confirmed using manual read. In addition, isolates of P. rettgeri providing MIC values ≥ 16 µg/mL with ceftazidime/avibactam should be retested using an alternate method to avoid major errors.

Results obtained with S. marcescens when using the Prompt Inoculation system and WalkAway read were outside of essential agreement compared to the reference method. Results obtained

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with this species should be confirmed using manual read.

Due to the occurrence of very major errors with all inoculation and read methods, isolates of Providencia stuartii that provide MICs of 4 and 8 µg/mL and isolates of P. aeruginosa that provide MICs of 4 µg/mL should be retested using an alternative/method.

The ability of the MicroScan Dried Gram Negative Panels to detect resistance to ceftazidime avibactam is unknown with C. freundii complex, C. koseri, M. morganii, and P. mirabilis because resistant strains were not available at the time of comparative testing. If such isolates are observed, they should be tested on an alternate method and/or submitted to a reference lab.

Elevated MICs with beta-lactam antimicrobials (e.g. ceftazidime/avibactam) may be observed if panels are over-inoculated with microorganisms such as Pseudomonas aeruginosa, Serratia spp., Proteus spp., Morganella spp., and Providencia spp. Inoculum concentration is critical with these antimicrobials as their mechanism of action involves disruption of bacterial cell wall synthesis. The user should pay careful attention to inoculum preparation, especially with manual methods that are technique dependent such as the Prompt system or inoculum prepared without the aid of a photometric device.

Enzyme group characterization was performed at the time of comparative testing with the exception of testing of OprD (outer membrane porin) for strains of Pseudomonas aeruginosa.

Ceftazidime/Avibactam is not active against Enterobacteriaceae bacteria that produce metallo-beta lactamases and may not have activity against gram-negative bacteria that overexpress efflux pumps or have porin mutations.

4. Special instrument requirements:

MicroScan panels can be read either manually or automatically on the WalkAway or autoSCAN-4 instrument systems.

I. Device Description:

The MicroScan Dried Gram-Negative MIC/Combo panel with ceftazidime/avibactam is used to determine the quantitative and/or qualitative antimicrobial agent susceptibility of aerobic and facultatively anaerobic gram negative bacilli colonies grown on solid media. After inoculation, panels are incubated for 16-20 hours at 35°C ± 1°C in a non-CO₂ incubator and read either visually or with MicroScan instrumentation according to the package insert.

Inoculation methods: Turbidity, Prompt Inoculation System

Read methods: Manual, MicroScan WalkAway System and MicroScan autoSCAN-4

J. Substantial Equivalence Information:

1. Predicate device name(s):

MicroScan Dried Gram Negative MIC/Combo Panels – Imipenem

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2. Predicate 510(k) number(s):

K162740

3. Comparison with predicate:

Table 1. Comparison with the Predicate

| Similarities | | |
| --- | --- | --- |
| Item | Device (K172337) | Predicate (K162740) |
| Device | MicroScan Dried Gram Negative MIC/Combo Panels – Ceftazidime/Avibactam | MicroScan Dried Gram Negative MIC/Combo Panels – Imipenem |
| Technology | Overnight microdilution MIC susceptibility | Same |
| Result Reported | Report results as minimum inhibitory concentration (MIC) and categorical interpretation (SIR) | Same |
| Read Methods | Manual and automated | Same |
| Inoculation Methods | Turbidity and Prompt | Same |
| Instrumentation | WalkAway or autoSCAN-4 Instrument systems | Same |
| Differences | | |
| Item | Device | Predicate |
| Intended Use | Determination of susceptibility to ceftazidime/avibactam with gram-negative bacteria | Determination of susceptibility to Imipenem with gram-negative bacteria |
| Antimicrobial Agent | Ceftazidime/avibactam 0.25/4–64/4 μg/mL | Imipenem 0.25 – 8 μg/mL |

# K. Standard/Guidance Document Referenced (if applicable):

1. Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA
2. CLSI M7-A10. Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically, January, 2015.
3. CLSI M100-S26. Performance Standards for Antimicrobial Susceptibility Testing; Twenty-Sixth Informational Supplement.

# L. Test Principle:

The antimicrobial susceptibility tests are dehydrated miniaturizations of the broth dilution susceptibility test. Various antimicrobial agents are diluted in Mueller Hinton broth supplemented with calcium and magnesium to concentrations spanning the range of clinical interest. Breakpoint Combo panels use concentrations equivalent to the categorical breakpoints of FDA and/or CLSI.

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After inoculation and rehydration with a standardized suspension of organism and incubation at 35°C for a minimum of 16 hours, the minimum inhibitory concentration (MIC) for the test organism is determined by observing the lowest antimicrobial concentration showing inhibition of growth.

## M. Performance Characteristics:

### 1. Analytical performance:

#### a. Precision/Reproducibility:

A reproducibility study was conducted at three external sites using 16 isolates of gram negative bacilli that were consistent with the intended use. The range of ceftazidime/avibactam dilutions tested was 0.03/4 to 64/4 µg/mL. Isolates were tested in triplicate over three days for a total of 432 data points. The isolates tested in the reproducibility study included C. freundii complex (one isolate), C. koseri (one isolate), E. cloacae (one isolate), E. coli (five isolates), K. oxytoca (one isolate), K. pneumoniae (three isolates), P. aeruginosa (three isolates) and S. marcescens (one isolate). Inocula were prepared using both the turbidity and Prompt method and results were read manually and with the WalkAway and autoSCAN-4 instrument systems. The majority of data points were on-scale and within ± one doubling dilution agreement as compared to the mode MIC (Table 2). Two data points were off-scale using the Prompt inoculation method and autoSCAN-4 read method. As shown in Table 2, the data was analyzed taking into consideration best case and worst case scenarios as described in the Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems:

https://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm080564.htm.

Table 2. Reproducibility with all Inoculation and Read Methods.

| Read Method | | Prompt Inoculation | Turbidity Inoculation |
| --- | --- | --- | --- |
| WalkAway | Best Case | 425/432 (98.4%) | 431/432 (99.8%) |
| | Worst Case | 425/432 (98.4%) | 431/432 (99.8%) |
| autoSCAN-4 | Best Case | 426/432 (98.6%) | 420/432 (97.2%) |
| | Worst Case | 426/432 (98.6%) | 420/432 (97.2%) |
| Manual | Best Case | 429/432 (99.3%) | 431/432 (99.8%) |
| | Worst Case | 429/432 (99.3%) | 431/432 (99.8%) |

The reproducibility results were acceptable.

#### b. Linearity/assay reportable range:

N/A

#### c. Traceability, Stability, Expected values (controls, calibrators, or methods):

Inoculum Density Check. A spectrophotometric device, the MicroScan Turbidity Meter was used to ensure quality control of the turbidity inoculum method. The turbidity inocula were

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prepared using the MicroScan Turbidity Meter with a reading of $0.08 \pm 0.02$ (equivalent to a $0.5\mathrm{McFarland}$ barium sulfate turbidity standard). The digital reading was recorded each day of use.

Organism density data was also collected during the Reproducibility phase of the study for suspensions prepared using the Prompt inoculum preparation method. Colony counts were performed weekly using the quality control strain $E$ coli ATCC 25922. Colony counts were also done once at each site for each reproducibility isolate.

All results were acceptable.

Purity Check. Purity check plates were evaluated; all AST results from a culture showing mixed growth were deleted and the test was repeated.

Growth Failure Rate. During the course of the study there were no growth failures with the MicroScan panel with ceftazidime/avibactam.

Organism integrity check. K. pneumoniae ATCC 700603 was tested with ceftazidime alone to check the integrity of the QC strain. All results were within the acceptable range.

Quality Control Testing. The CLSI and FDA recommended QC organisms (E. coli ATCC 25922, P. aeruginosa ATCC 27853, E. coli ATCC35218 and K. pneumoniae ATCC 700603) were tested using all inoculation and read methods using the extended range of dilutions of ceftazidime/avibactam $(0.03 / 4 - 64 / 4\mu \mathrm{g} / \mathrm{mL})$ . The reference panel was inoculated using the turbidity method only. Results are shown in Table 3.

Table 3. Quality Control Results with the Extended Dilution Range

| Organism | Conc. (μg/mL) | Ref | Prompt Inoculation Method | | | Turbidity Inoculation Method | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | | | Manual | WalkAway | AS4 | Manual | WalkAway | AS4 |
| E. coliATCC25922 | ≤0.03 | - | | | | | | |
| | 0.06 | - | 1 | 9 | 10 | 2 | 14 | 17 |
| | 0.12 | 120 | 159 | 148 | 148 | 158 | 143 | 141 |
| | 0.25 | 44 | 4 | 5 | 5 | 4 | 7 | 5 |
| | 0.5 | | | | | | | |
| | 1 | | | | | | | |
| | 2 | | | | | | | 1 |
| | 4 | | | | | | | |
| | 8 | | | | | | | |
| | 16 | | | | | | | |
| | 32 | | | | | | | |
| | 64 | | | | | | | |
| | >64 | | | | | | | |
| | | | | | | | | |
| P. aeruginosaATCC27853 | ≤0.03 | | | | | | | |
| | 0.06 | | | | | | | |
| | 0.12 | | | | | | | |
| | 0.25 | | | | | | | |
| | 0.5 | 1 | | | | 1 | | |
| | 1 | 93 | 83 | 84 | 98 | 111 | 120 | 130 |

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| Organism | Conc. (μg/mL) | Ref | Prompt Inoculation Method | | | Turbidity Inoculation Method | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | | | Manual | WalkAway | AS4 | Manual | WalkAway | AS4 |
| Expected Range 0.5 - 4 μg/mL | 2 | 69 | 77 | 73 | 63 | 49 | 40 | 30 |
| | 4 | 1 | 4 | 4 | 3 | 3 | 4 | 3 |
| | 8 | | | | | | | |
| | 16 | | | | | | | |
| | 32 | | | | | | | |
| | 64 | | | | | | | |
| | >64 | | | | | | | |
| | | | | | | | | |
| E. coli ATCC 35218 | ≤0.03 | 1 | 10 | 22 | 24 | 22 | 36 | 49 |
| | 0.06 | 158 | 142 | 133 | 128 | 137 | 125 | 112 |
| | 0.12 | 5 | 8 | 4 | 7 | 5 | 3 | 3 |
| | 0.25 | | | | | | | |
| | 0.5 | | 3 | 2 | 2 | | | |
| | 1 | | | | | | | |
| | 2 | | 1 | 1 | 1 | | | |
| | 4 | | | | | | | |
| | 8 | | | | | | | |
| | 16 | | | | | | | |
| | 32 | | | | | | | |
| | 64 | | | | | | | |
| | >64 | | | | | | | |
| | | | | | | | | |
| K. pneumoniae ATCC 700603 | ≤0.03 | | | | | | | |
| | 0.06 | | | | | | | |
| | 0.12 | | | | | | | |
| | 0.25 | | 1 | | | | | |
| | 0.5 | 157 | 149 | 150 | 154 | 156 | 156 | 158 |
| | 1 | 6 | 12 | 10 | 8 | 5 | 6 | 5 |
| | 2 | 1 | 1 | 1 | 2 | 2 | 2 | 1 |
| | 4 | | | | | | | |
| | 8 | | | | | | | |
| | 16 | | | | | | | |
| | 32 | | 1 | | | 1 | | |
| | 64 | | | | | | | |
| | >64 | | | | | | | |

The sponsor initially tested the QC strains in an extended range of ceftazidime/avibactam dilutions $(0.03 / 4 - 64 / 4)$ . The final dilution range included in the device was truncated to include ceftazidime/avibactam dilutions from $0.25 / 4$ to $64 / 4\mu \mathrm{g} / \mathrm{mL}$ . With the revised dilution range $(0.25 / 4 - 64 / 4\mu \mathrm{g} / \mathrm{mL})$ , the lower end of the expected QC range for $E.$ coli ATCC 25922 and $E.$ coli ATCC 35218 are off-scale. Because the lowest dilution in the QC range for $K.$ pneumoniae ATCC 700603 is $0.25\mu \mathrm{g} / \mathrm{mL}$ , some results obtained with this strain may also be off scale. The QC range for $P.$ aeruginosa ATCC 27853 are on-scale with the truncated range; because $P.$ aeruginosa ATCC 27853 will give on-scale results, it is the recommended QC strain for use with this panel. The following footnote to the QC table was included in the device labeling:

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The recommended QC strains for testing ceftazidime/avibactam on MicroScan panels are P. aeruginosa ATCC 27853 and K. pneumoniae ATCC 700603. Off-scale QC results could occur on certain panels with E. coli ATCC 25922, E. coli ATCC 35218 and K. pneumoniae ATCC 700603.

d. Detection limit:

N/A

e. Analytical specificity:

N/A

f. Assay cut-off:

N/A

2. Comparison studies:

a. Method comparison with predicate device:

The results obtained with the MicroScan Dried Gram-Negative MIC/Combo Panel with ceftazidime/avibactam were compared to results obtained using a frozen broth microdilution reference panel at three testing sites in the U.S. The reference panel was prepared according to CLSI M07-A10 guidelines except for the use of Pluronic-F in the inoculum water for the reference panel. A validation study was performed to demonstrate equivalence between reference panels inoculated with organisms suspended in water supplemented with Pluronic-F and reference panels inoculated with autoclaved distilled water without Pluronic-F. The effect of Pluronic F in the reference panel was determined with the following species: Citrobacter freundii (one isolate), Enterobacter cloacae (two isolates), Escherichia coli (three isolates), Klebsiella oxytoca (one isolate), Klebsiella pneumoniae (two isolates) and Pseudomonas aeruginosa (three isolates) and 11 replicates of each of four QC strains. The essential agreement (EA) of MIC values obtained using Pluronic-F as the diluent as compared to MIC values obtained using autoclaved distilled water as the diluent was 100%.

The initial studies included MicroScan and reference panels containing 12 dilutions of ceftazidime/avibactam (0.03/4 – 64/4 µg/mL) that were appropriate for the interpretive categories of the drug. The sponsor later modified the ceftazidime/avibactam dilution range to include a nine-dilution range (0.25/4 – 64/4 µg/mL).

For each organism tested, MicroScan panels and reference panels were inoculated using the same standardized suspension further diluted into 25 mL of water with either Pluronic-D (for the MicroScan dried panels) or Pluronic-F (for the frozen reference panels). Panels were inoculated using both the Prompt System and by the Turbidity method; MicroScan panels were read using the WalkAway, the autoSCAN4 and Manual Read. The reference panels were read manually. Performance was evaluated using FDA breakpoints for ceftazidime/avibactam, and results were analyzed based on the guidelines provided in the AST Class II Special Controls Guidance Document.

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An internal study was performed to determine the agreement of results obtained with the Prompt inoculation method using hold times of 0 hours and 4 hours prior to inoculation of the panels. Results of 4-hour holds were compared to 0-hour hold using the same inoculum and with expected results as determined by the reference method. Testing was performed with all three read methods using 20 replicates with each of four QC strains and 12 replicates of C. koseri. The study demonstrated that Prompt hold times up to four hours provided results within EA of the reference method.

A total of 79 P. aeruginosa clinical isolates were evaluated; of these 59 (74.7%) were fresh isolates and 20 (25.3%) were recent isolates. A total of 539 Enterobacteriaceae clinical isolates were evaluated including C. freundii (12 isolates), C. freundii complex (17 isolates), C. koseri (49 isolates), E. aerogenes (32 isolates), E. cloacae (48 isolates), E. coli (77 isolates), K. oxytoca (47 isolates), K. pneumoniae (88 isolates), M. morganii (41 isolates), P. mirabilis (56 isolates), P. rettgeri (19 isolates), P. stuartii (21 isolates) and S. marcescens (32 isolates). Of the 539 clinical isolates, 373 (69.2%) were fresh isolates, 149 (27.6%) were recent isolates and 17 (3.2%) were stock isolates.

A total of 29 challenge isolates of P. aeruginosa and 87 isolates of Enterobacteriaceae were evaluated. The Enterobacteriaceae isolates included C. freundii (2 isolates), C. freundii complex (4 isolates), C. koseri (13 isolates), E. aerogenes (4 isolates), E. cloacae (10 isolates), E. coli (16 isolates), K. oxytoca (8 isolates), K. pneumoniae (14 isolates), M. morganii (4 isolates), P. mirabilis (4 isolates), P. rettgeri (3 isolates), P. stuartii (1 isolate) and S. marcescens (4 isolates).

For the Enterobacteriaceae and for P. aeruginosa, the overall essential agreement and category agreement was acceptable at $\geq 90.0\%$ for the truncated dilutions (Tables 4 through 7). The essential agreement of evaluable results was initially evaluated using the long dilution range of ceftazidime/avibactam $(0.03/4 - 64/4\ \mu\mathrm{g/mL})$ and was found to be acceptable for each species tested; the overall EA of the evaluable results for Enterobacteriaceae was acceptable with both the long $(0.03/4 - 64/4\ \mu\mathrm{g/mL})$ and truncated dilutions $(0.25/4 - 64/4\ \mu\mathrm{g/mL})$.

Table 4. Performance of MicroScan Dried Gram-Negative Panels with Ceftazidime/Avibactam with Enterobacteriaceae, Prompt Inoculation Method, All Read Methods

| | Tot | No. EA | EA % | Eval EA Tot | No. Eval EA | Eval EA % | No. CA | CA % | No. R | No. S | min | maj | vmj |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| WalkAway | | | | | | | | | | | | | |
| Clinical | 539 | 510 | 94.6 | 46 | 40 | 87.0 | 533 | 98.9 | 2 | 537 | NA | 4 | 2 |
| Challenge | 87 | 85 | 97.7 | 31 | 30 | 96.8 | 85 | 97.7 | 16 | 71 | NA | 2 | 0 |
| Combined | 626 | 595 | 95.0 | 77 | 70 | 90.9 | 618 | 98.7 | 18 | 608 | NA | 6 | 2 |
| | | | | | | | | | | | | | |
| autoSCAN-4 | | | | | | | | | | | | | |
| Clinical | 539 | 527 | 97.8 | 43 | 37 | 86.0 | 537 | 99.6 | 2 | 537 | NA | 0 | 2 |
| Challenge | 87 | 85 | 97.7 | 32 | 31 | 96.9 | 85 | 97.7 | 16 | 71 | NA | 0 | 2 |
| Combined | 626 | 612 | 97.8 | 75 | 68 | 90.7 | 622 | 99.4 | 18 | 608 | NA | 0 | 4 |
| | | | | | | | | | | | | | |
| Manual | | | | | | | | | | | | | |
| Clinical | 539 | 527 | 97.8 | 48 | 42 | 87.5 | 537 | 99.6 | 2 | 537 | NA | 0 | 2 |
| Challenge | 87 | 86 | 98.9 | 31 | 30 | 96.8 | 86 | 98.9 | 16 | 71 | NA | 1 | 0 |
| Combined | 626 | 613 | 97.9 | 79 | 72 | 91.1 | 623 | 99.5 | 18 | 608 | NA | 1 | 2 |

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Table 5. Performance of MicroScan Dried Gram-Negative Panels with Ceftazidime/Avibactam with P. aeruginosa, Prompt Inoculation Method, All Read Methods

| | Tot | No. EA | EA % | Eval EA Tot | No. Eval EA | Eval EA % | No. CA | CA % | No. R | No. S | min | maj | vmj |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| WalkAway | | | | | | | | | | | | | |
| Clinical | 79 | 76 | 96.2 | 78 | 75 | 96.2 | 77 | 97.5 | 2 | 77 | NA | 1 | 1 |
| Challenge | 29 | 28 | 96.6 | 27 | 26 | 96.3 | 27 | 93.1 | 11 | 18 | NA | 1 | 1 |
| Combined | 108 | 104 | 96.3 | 105 | 101 | 96.2 | 104 | 96.3 | 13 | 95 | NA | 2 | 2 |
| | | | | | | | | | | | | | |
| autoSCAN-4 | | | | | | | | | | | | | |
| Clinical | 79 | 74 | 93.7 | 77 | 72 | 93.5 | 78 | 98.7 | 2 | 77 | NA | 0 | 1 |
| Challenge | 29 | 28 | 96.6 | 27 | 26 | 96.3 | 26 | 89.7 | 11 | 18 | NA | 1 | 2 |
| Combined | 108 | 102 | 94.4 | 104 | 98 | 94.2 | 104 | 96.3 | 13 | 95 | NA | 1 | 3 |
| | | | | | | | | | | | | | |
| Manual Read | | | | | | | | | | | | | |
| Clinical | 79 | 76 | 96.2 | 78 | 75 | 96.2 | 78 | 98.7 | 2 | 77 | NA | 1 | 0 |
| Challenge | 29 | 28 | 96.6 | 28 | 27 | 96.4 | 26 | 89.7 | 11 | 18 | NA | 1 | 2 |
| Combined | 108 | 104 | 96.3 | 106 | 102 | 96.2 | 104 | 96.3 | 13 | 95 | NA | 2 | 2 |

Table 6. Performance of MicroScan Dried Gram-Negative Panels with Ceftazidime/Avibactam with Enterobacteriaceae, Turbidity Inoculation Method, All Read Methods

| | Tot | No. EA | EA % | Eval EA Tot | No. Eval EA | Eval EA % | No. CA | CA % | No. R | No. S | min | maj | vmj |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| WalkAway | | | | | | | | | | | | | |
| Clinical | 539 | 535 | 99.3 | 47 | 44 | 93.6 | 536 | 99.4 | 2 | 537 | NA | 1 | 2 |
| Challenge | 87 | 85 | 97.7 | 33 | 33 | 100 | 86 | 98.9 | 16 | 71 | NA | 1 | 0 |
| Combined | 626 | 620 | 99.0 | 80 | 77 | 96.3 | 622 | 99.4 | 18 | 608 | NA | 2 | 2 |
| | | | | | | | | | | | | | |
| autoSCAN-4 | | | | | | | | | | | | | |
| Clinical | 539 | 535 | 99.3 | 45 | 42 | 93.3 | 537 | 99.6 | 2 | 537 | NA | 0 | 2 |
| Challenge | 87 | 86 | 98.9 | 35 | 34 | 97.1 | 87 | 100 | 16 | 71 | NA | 0 | 0 |
| Combined | 626 | 621 | 99.2 | 80 | 76 | 95.0 | 624 | 99.7 | 18 | 608 | NA | 0 | 2 |
| | | | | | | | | | | | | | |
| Manual Read | | | | | | | | | | | | | |
| Clinical | 539 | 533 | 98.9 | 47 | 45 | 95.7 | 536 | 99.4 | 2 | 537 | NA | 1 | 2 |
| Challenge | 87 | 87 | 100 | 33 | 33 | 100 | 87 | 100 | 16 | 71 | NA | 0 | 0 |
| Combined | 626 | 620 | 99.0 | 80 | 78 | 97.5 | 623 | 99.5 | 18 | 608 | NA | 1 | 2 |

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Table 7. Performance of MicroScan Dried Gram-Negative Panels with Ceftazidime/Avibactam with $P$ . aeruginosa, Turbidity Inoculation Method, All Read Methods

| | Tot | No. EA | EA % | Eval EA Tot | No. Eval EA | Eval EA % | No. CA | CA % | No. R | No. S | min | maj | vmj |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| WalkAway | | | | | | | | | | | | | |
| Clinical | 79 | 78 | 98.7 | 78 | 77 | 98.7 | 78 | 98.7 | 2 | 77 | NA | 0 | 1 |
| Challenge | 29 | 28 | 96.6 | 28 | 27 | 96.4 | 25 | 86.2 | 11 | 18 | NA | 2 | 2 |
| Combined | 108 | 106 | 98.1 | 106 | 104 | 98.1 | 103 | 95.4 | 13 | 95 | NA | 2 | 3 |
| | | | | | | | | | | | | | |
| autoSCAN-4 | | | | | | | | | | | | | |
| Clinical | 79 | 76 | 96.2 | 78 | 75 | 96.2 | 78 | 98.7 | 2 | 77 | NA | 0 | 1 |
| Challenge | 29 | 28 | 96.6 | 27 | 26 | 96.3 | 26 | 89.7 | 11 | 18 | NA | 1 | 2 |
| Combined | 108 | 104 | 96.3 | 105 | 101 | 96.2 | 104 | 96.3 | 13 | 95 | NA | 1 | 3 |
| | | | | | | | | | | | | | |
| Manual Read | | | | | | | | | | | | | |
| Clinical | 79 | 78 | 98.7 | 78 | 77 | 98.7 | 79 | 100 | 2 | 77 | NA | 0 | 0 |
| Challenge | 29 | 27 | 93.1 | 28 | 26 | 92.9 | 26 | 89.7 | 11 | 18 | NA | 1 | 2 |
| Combined | 108 | 105 | 97.2 | 106 | 103 | 97.2 | 105 | 97.2 | 13 | 95 | NA | 1 | 2 |

For $P$ rettgeri the EA for isolates tested using Prompt inoculation and Walkaway read was $50.0\%$ . The essential agreement of tests prepared and interpreted with other combinations of inoculation and read methods was acceptable at $>90.0\%$ . In addition, isolates of $P$ rettgeri gave MIC values resulting in major errors when tested using the Prompt inoculation method with WalkAway read and with the Turbidity inoculation method with both WalkAway and Manual read. To address the lack of EA and the potential for major errors for $P$ rettgeri, the following limitation was included in the device labeling:

Results obtained with $P$ rettgeri and ceftazidime/avibactam with the Prompt Inoculation system and WalkAway read were outside of essential agreement compared to the reference method; results should be confirmed using manual read. In addition, isolates of $P$ rettgeri providing MIC values $\geq 16\mu \mathrm{g / mL}$ with ceftazidime/avibactam should be retested using an alternate method to avoid major errors.

For S. marcescens, the EA for isolates tested using Prompt inoculation and Walkaway read was $75.0\%$ . The essential agreement of tests prepared and interpreted with other combinations of inoculation and read methods for these two species were acceptable at $>90.0\%$ . The following limitation was included in the device labeling:

Results obtained with S. marcescens when using the Prompt Inoculation system and WalkAway read were outside of essential agreement compared to the reference method. Results obtained with this species should be confirmed using manual read.

There was a total of 13 resistant strains of $P$ aeruginosa and 2 resistant isolates of $P$ stuartii included in the study. Some isolates of these two species gave MIC values resulting in very major errors when tested with all inoculation and read methods; the percent of very major errors was $100\%$ (2/2) for $P$ stuartii. The percent of very major errors obtained with $P$ aeruginosa ranged from 15.4 to $23.1\%$ (2/13 and 3/13) for $P$ aeruginosa. One isolate of $P$ aeruginosa that gave a very major error during the clinical study (reference method result, $16~\mu \mathrm{g / mL}$ , MicroScan result, $4~\mu \mathrm{g / mL}$ ) was retested multiple times with the reference

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method; all replicate testing with the reference method showed MIC values of 4 µg/mL for this isolate, which demonstrates agreement with the original MicroScan panel results. Because ceftazidime/avibactam has no intermediate breakpoint, some MIC values for these two species resulted in very major errors but were within EA of the reference method. The very major error rate was adjusted to reflect results within EA; the adjusted very major rate for P. aeruginosa was 7.7% (1/13) for all inoculation and read methods. The adjusted very major error rate for P. stuartii was 0% (Prompt with WalkAway. Prompt with Manual read and Turbidity with WalkAway) or 50% (Prompt with autoSCAN-4, Turbidity with autoSCAN-4 and Turbidity with manual read) for P. stuartii. Due to the potential for very major errors with P. stuartii and P. aeruginosa for isolates that give MIC values of 4 and 8 µg/mL, the following limitation was included in the device labeling:

Due to the occurrence of very major errors with all inoculation and read methods, isolates of Providencia stuartii that provide MICs of 4 and 8 µg/mL and isolates of P. aeruginosa that provide MICs of 4 µg/mL should be retested using an alternative/method.

In addition, to address the very major error rate observed with P. aeruginosa and P. stuartii, and the lack of an intermediate breakpoint for ceftazidime/avibactam the following footnote was added to the performance table:

The overall very major error rate for Enterobacteriaceae with Prompt inoculation and Walkaway read was 11.1% (n=2/18, both errors with Providencia stuartii). All very major errors were one dilution apart from the reference method and as such fall within essential agreement. Based on the essential agreement and lack of an intermediate breakpoint for ceftazidime/avibactam, the adjusted very major error rate for Enterobacteriaceae is 0%.

The overall very major error rate for P. aeruginosa with Prompt inoculation and Walkaway read was 15.4% (n=2/13). One of the very major errors was one dilution apart from the reference method and as such fell within essential agreement. Based on the essential agreement and the lack of an intermediate breakpoint for ceftazidime/avibactam, the adjusted very major error rate for P. aeruginosa is 7.7%. For the second P. aeruginosa isolate providing a very major error, replicate testing of the reference method gave results identical to those obtained with the MicroScan panel.

No resistant strains were evaluated for the following species: C. freundii complex, C. koseri, M. morganii, and P. mirabilis. The following limitation was included in the device labeling to reflect the undetermined ability of the MicroScan panel to detect resistance in these species:

The ability of the MicroScan Dried Gram Negative Panels to detect resistance to ceftazidime avibactam is unknown with C. freundii complex, C. koseri, M. morganii, and P. mirabilis because resistant strains were not available at the time of comparative testing. If such isolates are observed, they should be tested on an alternate method and/or submitted to a reference lab.

The following limitation was added to the device labeling to reflect potential erroneous results that may occur based on inaccurate inoculum concentrations, especially with manual inoculum preparation methods:

Elevated MICs with beta-lactam antimicrobials (e.g. ceftazidime/avibactam) may be observed if panels are over-inoculated with microorganisms such as Pseudomonas

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aeruginosa, Serratia spp., Proteus spp., Morganella spp., and Providencia spp. Inoculum concentration is critical with these antimicrobials as their mechanism of action involves disruption of bacterial cell wall synthesis. The user should pay careful attention to inoculum preparation, especially with manual methods that are technique dependent such as the Prompt system or inoculum prepared without the aid of a photometric device.

## Enzyme Group Molecular Characterization

Isolates of Enterobacteriaceae and *P. aeruginosa* harboring various molecular mechanisms of resistance noted in the FDA drug label were tested with ceftazidime/avibactam. The following resistance mechanisms were evaluated: cAmpC, IMP, OXA, KPC, SME, TEM, NDM, CMY, SHV, CTX-M, OMPC, OMPK, PDC, GES, and VEB.

To address resistance mechanisms not tested, the following limitation was added to the device labeling:

Enzyme group characterization was performed at the time of comparative testing with the exception of testing of OprD (outer membrane porin) for strains of Pseudomonas aeruginosa.

In addition, to address resistance mechanisms against which ceftazidime/avibactam may not be active, the following limitation was added to the device labeling:

Ceftazidime/Avibactam is not active against Enterobacteriaceae bacteria that produce metallo-beta lactamases and may not have activity against gram-negative bacteria that overexpress efflux pumps or have porin mutations.

## MIC Trending

An analysis of trending was conducted using the combined clinical and challenge data for *P. aeruginosa* and for Enterobacteriaceae using the long ceftazidime/avibactam dilution range of 0.03 – 64 µg/mL. This trending calculation takes into account MIC values that are determined to be one or more doubling dilution lower or higher compared to the reference method irrespective of whether the device MIC values are on-scale or not.

The data for 107 *P. aeruginosa* results determined to be evaluable for trending analysis showed no evidence of trending.

The data for 532 Enterobacteriaceae results determined to be evaluable for trending analysis showed evidence of low trending for panels inoculated using the Prompt inoculation method and read using autoSCAN-4 or for panels inoculated using the turbidity inoculation method and read using the WalkAway or Manual read methods. The following footnote to the performance table was added to the device labeling:

Ceftazidime/Avibactam MIC values for Enterobacteriaceae were most frequently in exact agreement with the reference method. When not in agreement, results by Prompt/autoSCAN-4 read and Turbidity/WalkAway and Manual read tended to be at least one doubling dilution lower than the reference method.

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b. Matrix comparison:

N/A

3. Clinical studies:

a. Clinical Sensitivity:

N/A

b. Clinical specificity:

N/A

c. Other clinical supportive data:

N/A

4. Clinical cut-off:

N/A

5. Expected values/Reference range:

Table 8. Breakpoints and Interpretive Categories for Ceftazidime/Avibactam (FDA Drug Label)

| Organism | FDA Interpretive Criteria for Ceftazidime/Avibactam MIC (μg/mL) | | |
| --- | --- | --- | --- |
| | S | I | R |
| Enterobacteriaceae and P. aeruginosa | ≤ 8/4 | NA | ≥ 16/4 |

N. Proposed Labeling:

The labeling is sufficient and it satisfies the requirements of 21 CFR Part 809.10.

O. Conclusion:

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