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Intended Use: To determine bacterial antimicrobial agent susceptibility
Indications for Use: The MicroScan MICroSTREP plus® Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of aerobic streptococci, including Streptococcus pneumoniae. After inoculation, panels are incubated for 20 - 24 hours at 35°C +/- 1°C in a non-CO2 incubator, and read visually according to the Package Insert. Additionally, the panels may be incubated in and read by a MicroScan® WalkAway instrument.

This particular submission is for the addition of instrument read capability of the antimicrobial Azithromycin, at concentrations of 0.12 to 4 mcg/m1 on the MicroScan MICroSTREP plus® Panel.

The organisms which may be used for Azithromycin susceptibility testing in this panel are:

Streptococcus pneumoniae (including penicillin-resistant strains) Streptococcus pyogenes Streptococcus agalactiae Streptococci (Groups C, F, G) viridans group streptococci

The MicroScan MICroSTREP plus® Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of aerobic streptococci, including Streptococcus pneumoniae. After inoculation, panels are incubated for 20 - 24 hours at 35°C +/-1 °C in a non-CO2 incubator, and read according to the Package Insert.

The antimicrobial susceptibility tests are miniaturizations of the broth dilution susceptibility test. Various antimicrobial agents are diluted in water, buffer or minute concentrations of broth to concentrations bridging the range of clinical interest. Panels are rehydrated with 115 µl Mueller-Hinton broth supplemented with 2-5% lysed horse blood (LHB) and buffered with 50 mM HEPES, after inoculation of the broth with a standardized suspension of the organism in saline. After incubation in a non-CO2 incubator for 20-24 hours, the minimum inhibitory concentration (MIC) for the test organism is manually read by observing the lowest antimicrobial concentration showing inhibition of growth. Additionally, the panels may be incubated in and read by a MicroScan® WalkAway instrument.

Here's an analysis of the provided text, focusing on the acceptance criteria and study details for the MicroScan MICroSTREP plus® Panel with Azithromycin:

1. Table of Acceptance Criteria and Reported Device Performance

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size: The document mentions "stock and CDC Challenge strains" were used for the external evaluation, but it does not specify the exact number of strains or isolates used in the test set.
• Data Provenance: The study involved an "external evaluation," which suggests the data was collected outside of the manufacturer's internal lab. The use of "stock and CDC Challenge strains" implies a mix of strains with known characteristics, likely derived from various sources. The document does not explicitly state the country of origin, but "CDC Challenge strains" suggests a U.S.-centric source for at least some of the strains. The study appears to be prospective in nature, as it was designed to confirm the acceptability of the proposed instrument read method.

3. Number of Experts Used to Establish Ground Truth for the Test Set and Their Qualifications

The document states that the performance was compared with an "expected result generated on a CLSI frozen Reference Panel, as defined in the FDA document 'Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA', dated February 5, 2003." This implies that the ground truth was established by adherence to a recognized standard (CLSI reference method) rather than by individual experts.

• Number of Experts: Not applicable in the context of this ground truth method.
• Qualifications of Experts: Not applicable. The ground truth relies on a standardized reference method.

4. Adjudication Method for the Test Set

The document does not describe an adjudication method in the traditional sense of multiple human readers or experts resolving discrepancies. Instead, it refers to comparing the instrument read results against "Expected Results determined before the evaluation" which were generated using a CLSI frozen Reference Panel. This suggests a direct comparison to a standardized, pre-established reference.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

• No, a MRMC comparative effectiveness study was not done. The study's focus was on the performance of the instrument read method compared to a reference standard, not on comparing human readers with and without AI assistance. The device is an automated instrument reader, effectively a "standalone" algorithm for reading MIC results.

6. Standalone (Algorithm Only) Performance Study

• Yes, a standalone performance study was done. The entire evaluation described is focused on the "proposed instrument read method" (i.e., the MicroScan® WalkAway instrument's automated reading capability) for the MICroSTREP plus® Panel. This is a standalone performance assessment of the instrument's ability to read MIC results.

7. Type of Ground Truth Used

• Reference Standard / Expert Consensus (Indirectly): The ground truth was established by an "expected result generated on a CLSI frozen Reference Panel, as defined in the FDA document 'Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA'." This represents a widely accepted and standardized method for determining antimicrobial susceptibility, which is itself based on extensive expert consensus and validation within the microbiology community.

8. Sample Size for the Training Set

• The document does not provide information on the sample size for a training set. This is a commercial device for determining antimicrobial susceptibility, and the "instrument read method" typically relies on an existing, validated algorithm. While the algorithm would have been trained at some point, the 510(k) summary focuses on the validation of the instrument's read capability for Azithromycin specifically, rather than the initial development and training of the core reading algorithm. Therefore, details about algorithm training data are not presented for this specific submission.

9. How the Ground Truth for the Training Set Was Established

• Not specified in this document. As mentioned above, the document does not detail the training set or the method for establishing its ground truth. For AST systems, the ground truth for training would typically involve either manual readings by trained microbiologists following CLSI guidelines, or comparisons to established reference methods (like macrobroth dilution).

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The MicroScan® MICroSTREP plus™ Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of aerobic streptococci, including Streptococcus pneumoniae. After inoculation, panels are incubated for 20 - 24 hours at 35°C +/- 1°C in a non-CO2 incubator, and read visually according to the Package Insert.

To determine bacterial antimicrobial agent susceptibility

This particular submission is for the addition of the antimicrobial Azithromycin at concentrations of 0.12 to 4 mcg/ml to the test panel

The organisms which may be used for Azithromycin susceptibility testing in this panel are:

Streptococcus pneumoniae
Streptococcus pyogenes
Streptococcus agalactiae
streptococci (Groups C. F. G)
viridans group streptococci

The MicroScan® MICroSTREP plus™ Panel is used to determine quantitative and/or qualitative antimicrobial agent susceptibility of colonies grown on solid media of aerobic streptococci, including Streptococcus pneumoniae. After inoculation, panels are incubated for 20 - 24 hours at 35°C +/- 1°C in a non-CO2 incubator, and read visually according to the Package Insert.

The antimicrobial susceptibility tests are miniaturizations of the broth dilution susceptibility test. Various antimicrobial agents are diluted in water, buffer or minute concentrations of broth to concentrations bridging the range of clinical interest. Panels are rehydrated with 115 ul Mueller-Hinton broth supplemented with 2-5% lysed horse blood (LHB) and buffered with 50 mM HEPES, after inoculation of the broth with a standardized suspension of the organism in saline. After incubation in a non-CO2 incubator for 20-24 hours, the minimum inhibitory concentration (MIC) for the test organism is manually read by observing the lowest antimicrobial concentration showing inhibition of growth.

Here's an analysis of the provided text, outlining the acceptance criteria and study details for the MicroScan® MICroSTREP plus™ Panel for Azithromycin susceptibility testing:

Acceptance Criteria and Device Performance Study

1. Table of Acceptance Criteria and Reported Device Performance

Note: The document explicitly states the acceptance criteria for Essential Agreement as "acceptable performance," and then provides the 99.3% result. For reproducibility and quality control, it simply states "acceptable reproducibility and precision" and "acceptable results," implying these met their internal criteria without providing a specific quantitative benchmark in the summarized text.

2. Sample Size Used for the Test Set and Data Provenance

• Test Set Sample Size: The document indicates the external evaluation was conducted with "fresh and stock Efficacy isolates and stock Challenge strains" for streptococcal isolates. However, a specific number for the sample size (number of isolates/strains) is not provided in the summary.
• Data Provenance: The study was an "external evaluation," suggesting it was conducted by an entity separate from the manufacturer. The document doesn't specify the country of origin of the data, but the context is a submission to the FDA in the USA. It's unclear whether the data was retrospective or prospective, though "fresh and stock isolates" suggest a mix, potentially with fresh isolates being prospective and stock isolates being retrospective.

3. Number of Experts Used to Establish Ground Truth and Their Qualifications

The document does not provide any information about the number of experts used or their qualifications to establish the ground truth.

4. Adjudication Method for the Test Set

The document does not provide any information about an adjudication method. The comparison was made against an "NCCLS frozen Reference panel."

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

An MRMC comparative effectiveness study was not performed or reported. The study focuses on the standalone performance of the device against a reference method, not the impact of AI assistance on human readers.

6. Standalone Performance Study

Yes, a standalone study was done. The entire premise of the submission is to demonstrate the performance of the MicroScan® MICroSTREP plus™ Panel (an algorithm/device) in determining antimicrobial susceptibility. Its performance (Essential Agreement) was compared directly to an "NCCLS frozen Reference panel."

7. Type of Ground Truth Used

The ground truth used was an NCCLS frozen Reference Panel. This panel serves as the established gold standard for determining antimicrobial susceptibility in this context. While not explicitly stated as "expert consensus" or "pathology," a reference panel developed by organizations like NCCLS (now CLSI) inherently represents a consensus on accurate susceptibility determination methods.

8. Sample Size for the Training Set

The document does not provide any information about a training set sample size. This type of device relies on established biological and chemical reactions interpreted via a defined protocol, rather than a machine learning model that typically requires a large training set.

9. How the Ground Truth for the Training Set Was Established

As no training set is mentioned in the context of machine learning, the question of how its ground truth was established is not applicable. The device's operational principles are based on known antimicrobial agent concentrations and visual interpretation of bacterial growth inhibition against an established reference method (NCCLS frozen Reference Panel) for validation.

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