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To determine bacterial antimicrobial agent susceptibility

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 Chloramphenicol, at concentrations of 1 to 32 mcg/ml on the MicroScan MICroSTREP plus ® Panel.

The organisms which may be used for Chloramphenicol susceptibility testing on this panel are: Susceptible streptococci, including Streptococcus pneumoniae

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 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. Additionally, the panels may be incubated in and read by a MicroScan® WalkAway instrument.

The provided text describes the 510(k) summary for the MicroScan MICroSTREP plus® Panel for determining bacterial susceptibility to Chloramphenicol using the MicroScan® WalkAway instrument.

Here's an analysis of the acceptance criteria and study information:

1. Table of Acceptance Criteria and Reported Device Performance:

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

• Sample Size: Not explicitly stated as a single number. The study used "stock and CDC Challenge strains." The FDA guidance cited for AST systems would typically define the minimum number of isolates required for evaluation, but this specific number is not provided in the summary.
• Data Provenance: The study was an "external evaluation" conducted with "stock and CDC Challenge strains." This suggests a combination of curated and potentially geographically diverse strains, but specific countries of origin are not mentioned. The study appears to be prospective in the sense that the device was evaluated on these strains to confirm its performance against pre-established expected results.

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

• Number of Experts: Not explicitly stated.
• Qualifications of Experts: Not explicitly stated. However, the ground truth was established by a "CLSI frozen Reference Panel," which implies that the "Expected Results" were determined by established, standardized methods and likely confirmed by expert microbiologists or reference laboratories adhering to Clinical and Laboratory Standards Institute (CLSI) guidelines.

4. Adjudication Method for the Test Set:

• The text describes comparing the instrument-read results "with an expected result generated on a CLSI frozen Reference Panel." This indicates a direct comparison to a pre-defined reference standard rather than an adjudication process between multiple human readers for the specific device test itself.

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

• No, a multi-reader multi-case (MRMC) comparative effectiveness study was not performed. The study focuses on evaluating the instrument's performance against a reference standard, not on comparing human reader performance with and without AI assistance.

6. Standalone (Algorithm Only) Performance:

• Yes, a standalone performance study was done. The entire premise of the submission is to demonstrate the performance of the MicroScan® WalkAway instrument (which automates the reading process) when determining susceptibility to Chloramphenicol on the MICroSTREP plus® Panel. The "Essential Agreement of 100% for Chloramphenicol instrument read results compared with the Expected Result" directly reflects the standalone performance of the instrument/algorithm.

7. Type of Ground Truth Used:

• Expert Consensus / Reference Standard: The ground truth was established as "Expected Results determined before the evaluation" using a "CLSI frozen Reference Panel." This implies that the expected MIC values were determined through recognized, standardized laboratory methods, likely involving expert consensus on the interpretation of those reference methods (e.g., broth microdilution or agar dilution as per CLSI guidelines).

8. Sample Size for the Training Set:

• The document does not specify a separate training set. This is a 510(k) submission for a device that uses an instrument to read pre-determined assays. The "instrument read method" performance is being evaluated, implying the instrument's reading capabilities were developed and validated prior to this submission. The text focuses on the test set performance to show equivalence. In older submissions for IVD devices, explicit training/validation splits with detailed sample sizes were not always outlined as they might be for modern AI/ML systems.

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

• As no separate training set is explicitly mentioned, the method for establishing ground truth for a training set is not provided. The development of the WalkAway instrument's reading algorithm would have involved its own internal validation and calibration processes, but these details are not part of this 510(k) summary. The "Expected Results" for the test set were based on the CLSI frozen Reference Panel.

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To determine bacterial antimicrobial agent susceptibility. 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. This particular submission is for the addition of the antimicrobial Chloramphenicol at concentrations of 1 to 32 mcg/ml to the test panel. The organisms which may be used for Chloramphenicol susceptibility testing in this panel are: Susceptible streptococci, including Streptococcus pneumoniae.

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 (MC) for the test organism is manually read by observing the lowest antimicrobial concentration showing inhibition of growth.

Here's a breakdown of the acceptance criteria and study information for the MicroScan® MICroSTREP plus™ Panel, based on the provided text:

1. Acceptance Criteria and Reported Device Performance

Note: The document explicitly states the acceptance criteria were "as defined in the FDA DRAFT document 'Guidance on Review Criteria for Assessment of Antimicrobial Susceptibility Devices', dated March 8, 2000." However, the specific numerical thresholds for "acceptable reproducibility" and "acceptable results for Quality Control" are not detailed in the provided text. The only specific quantitative criterion mentioned is for "Essential Agreement."

2. Sample Size and Data Provenance

• Test Set Sample Size: Not explicitly stated as a number. The external evaluation was conducted with "fresh and stock Efficacy isolates and stock Challenge strains." The specific number of isolates for each category is not provided.
• Data Provenance: Not explicitly stated by country of origin. The study was an "external evaluation" and compared performance against an "NCCLS frozen Reference Panel." NCCLS (National Committee for Clinical Laboratory Standards) is a US-based organization (now CLSI), suggesting the data is likely US-centric or from facilities following US standards. The study appears to be retrospective as it uses existing "stock" isolates and a reference panel.

3. Number and Qualifications of Experts for Ground Truth

• The document does not specify the number of experts or their qualifications used to establish the ground truth for the test set.
• The ground truth reference method was the "NCCLS frozen Reference Panel," which implies that the reference panel itself's values (likely MICs) were established through a standardized, expert-validated process at the time of its creation, but details are not provided here.

4. Adjudication Method for the Test Set

• The document does not specify an adjudication method like 2+1 or 3+1. The comparison was described as direct, "comparing its performance with an NCCLS frozen Reference panel."

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

• No, an MRMC comparative effectiveness study was not done. This device is a test panel for determining antibiotic susceptibility, not an imaging device that involves human readers interpreting results in a comparative study with and without AI assistance. The panel results are visually read by a human, but the study focuses on the accuracy of the panel itself against a reference method, rather than the improvement of human interpretation with AI.

6. Standalone (Algorithm Only) Performance Study

• Yes, in essence, a standalone performance study was done. The MicroScan® MICroSTREP plus™ Panel's performance was evaluated by directly comparing its results (after manual visual reading) against the "NCCLS frozen Reference panel." While a human reads the final MIC, the "device" in question (the panel and its methodology) is evaluated on its ability to produce accurate MIC values independently of specific human reader variability beyond what is inherent in visual reading. The study aimed to show the panel's inherent performance.

7. Type of Ground Truth Used

• The ground truth used was established by an NCCLS frozen Reference Panel. This type of ground truth represents a reference standard method that is widely accepted in microbiology for determining minimum inhibitory concentrations (MICs). It is typically established through rigorous, standardized procedures, often reflecting expert consensus on the methodologies.

8. Sample Size for the Training Set

• The document does not explicitly mention a separate "training set" or its sample size. The information provided focuses on the evaluation of the device against a reference. For a device like this (which appears to be a chemical assay system rather than an AI/ML algorithm that requires explicit machine learning training), the concept of a "training set" in the context of AI is not directly applicable. The development of the panel itself would have involved extensive R&D and optimization, but not in the sense of a machine learning training set described here.

9. How Ground Truth for the Training Set Was Established

• As there's no explicitly mentioned "training set" in the AI/ML context, there's no information on how its ground truth was established. The development process for a chemical assay panel would rely on established microbiological principles and validated experimental results to optimize the concentrations and reagents, not on a machine learning training process.

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