VITEK® 2 Streptococcus Levofloxacin is designed for antimicrobial susceptibility testing of Streptococcus species. VITEK 2 Streptococcus Levofloxacin is a quantitative test intended for use with the VITEK® 2 and VITEK® 2 Compact Systems as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents. Levofloxacin has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.

Active in vitro and in clinical infections Streptococcus pneumoniae (including multi-drug resistant strains [MDRSP]) Streptococcus pyogenes

Active in vitro but clinical significance unknown β-hemolytic Streptococcus (Group C/F) B-hemolytic Streptococcus (Group G) Streptococcus agalactiae Streptococcus milleri Viridans group Streptococci

The VITEK® 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK® 2 System for the automated quantitative or qualitative susceptibility testing of isolated colonies for the most clinically significant aerobic gram-negative bacilli, Staphylococcus spp., Enterococcus spp., Streptococcus spp. and clinically significant yeast.

Device Description

The VITEK 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique for determining the minimum inhibitory concentration (MIC). Each VITEK 2 AST card contains 64 wells. A control well which only contains microbiological culture media is resident on all cards. The remaining wells contain premeasured portions of a specific antibiotic combined with culture media. The bacterial or yeast isolate to be tested is diluted to a standardized concentration with 0.45 - 0.5% saline before being used to rehydrate the antimicrobial medium within the card. The VITEK 2 System automatically fills, seals and places the card into the incubator/reader. The VITEK 2 Compact has a manual filling, sealing and loading operation. The VITEK 2 Systems monitor the growth of each well in the card over a defined period of time. At the completion of the incubation cvcle, a report is generated that contains the MIC value along with the interpretive category result for each antibiotic contained on the card.

The VITEK 2 Streptococcus Levofloxacin has the following concentrations in the card: 1. 2. 4 and 16 ug/mL (equivalent standard method concentration by efficacy in ug/mL). The MIC result range for the VITEK 2 card is ≤ 0.25 -> 16ug/mL.

AI/ML Overview

This document describes the VITEK® 2 Streptococcus Levofloxacin system, a device for antimicrobial susceptibility testing of Streptococcus species, and its performance evaluation for FDA 510(k) clearance.

1. Acceptance Criteria and Reported Device Performance

The acceptance criteria for the VITEK® 2 Streptococcus Levofloxacin system are not explicitly stated as quantitative thresholds in the provided text. However, standard AST guidance documents and FDA interpretive criteria are referenced, implying the following would be the acceptance criteria. The reported device performance is derived from the "Method comparison with predicate device" section.

Metric	Acceptance Criteria (Implied from Guidance)	Reported Device Performance (Clinical + Challenge combined)
Essential Agreement (EA)	High percentage (typically >90-95%)	99.0%
Category Agreement (CA)	High percentage (typically >90-95%)	97.9%
Major Discrepancies (maj)	Low (typically <3%)	0 (0%)
Very Major Discrepancies (vmj)	Low (typically <3%)	0 (0%)
Minor Discrepancies (min)	Low (typically <7%)	32 (2.1%)

Note on Minor Discrepancies: All 32 minor errors observed involved a shift from "Susceptible" by the reference method to "Intermediate" by the VITEK system. This indicates a slightly conservative bias in the VITEK system's interpretation for these cases.

2. Sample Size and Data Provenance

Test Set Sample Size:
- Clinical Isolates: 1338
- Challenge Isolates: 207
- Total Combined Test Set: 1545 isolates
Data Provenance: The isolates were sourced from clinical specimens, with the majority being recently isolated. These studies were conducted at four external clinical sites. The country of origin of the data is not explicitly stated, but clinical studies for FDA clearance are typically conducted within the US or its territories, or in regions where clinical practices align with US standards. The study appears to be retrospective for the clinical isolates (recently isolated from clinical specimens) and prospective for the challenge isolates (a specifically evaluated set).

3. Number and Qualifications of Experts for Ground Truth

The document does not specify the number of experts used or their specific qualifications (e.g., radiologist with 10 years of experience) for establishing ground truth. The ground truth was established by a CLSI broth microdilution reference method, which is a standardized laboratory procedure, not typically relying on expert interpretation in the same way as, for example, image-based diagnostics.

4. Adjudication Method

The concept of an "adjudication method" (like 2+1 or 3+1) is typically applied in studies where multiple human readers or experts independently assess cases, and their discrepancies are resolved through a structured process. In this context of antimicrobial susceptibility testing, the CLSI broth microdilution reference method served as the gold standard, removing the need for a human-based adjudication process for the test set interpretation. Discrepancies between the device and the reference method were identified and categorized as major, very major, or minor.

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

No MRMC comparative effectiveness study was done. This type of study investigates how human readers' performance changes with AI assistance. The VITEK 2 system is an automated device designed to replace or assist traditional AST methods, rather than directly assisting human readers in interpreting results from other sources.

6. Standalone Performance Study

Yes, a standalone performance study was done. The entire performance evaluation described in section M (Performance Characteristics) and section 2.a (Method comparison with predicate device) evaluates the algorithm's performance (the VITEK 2 system) directly against a gold standard (CLSI broth microdilution reference method), without human intervention in the interpretation of the VITEK 2 results.

7. Type of Ground Truth Used

The type of ground truth used was the CLSI broth microdilution reference method. This is a well-established and standardized laboratory method for determining minimum inhibitory concentrations (MICs) of antimicrobials. It serves as the gold standard for AST.

8. Sample Size for the Training Set

The document does not explicitly state a separate "training set" sample size. For an AST system like VITEK 2, the development typically involves extensive internal testing and refinement using a large, diverse collection of isolates before formal comparative studies are conducted for regulatory submission. The provided sample sizes (1338 clinical and 207 challenge isolates) pertain to the test set used for the formal performance evaluation.

9. How Ground Truth for the Training Set was Established

Since a separate "training set" is not explicitly mentioned as distinct from the test set in the context of this submission, the method for establishing ground truth for any internal development/training would likely also have been the CLSI broth microdilution reference method or a similar validated reference method, given its role as the industry standard. However, the specific details for any such internal "training set" are not provided in this document.

Summary

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

A. 510(k) Number:

K112228

B. Purpose for Submission:

To obtain a substantial equivalence determination for this premarket notification for the addition of Levofloxacin to the VITEK 2 and VITEK 2 Compact Antimicrobial Susceptibility Test (AST) Systems.

C. Measurand:

Levofloxacin concentrations of 1, 2, 4 and 16 ug/mL are included in the VITEK® 2 Streptococcus Levofloxacin card.

D. Type of Test:

The minimum inhibitory concentration (MIC) is determined using qualitative growth based detection algorithm using predetermined growth threshold. The MIC reporting result range of the card is ≤ 0.25 -> 16 µg/mL.

E. Applicant:

bioMerieux, Inc.

F. Proprietary and Established Names:

VITEK® 2 Streptococcus Levofloxacin

G. Regulatory Information:

Product Code	Classification	Regulation Section	Panel
LON	Class II	21 CFR 866.1645	Microbiology

H. Intended Use:

1. Intended use(s):
  VITEK® 2 Streptococcus Levofloxacin is designed for antimicrobial susceptibility testing of Streptococcus species. VITEK 2 Streptococcus

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Levofloxacin is a quantitative test intended for use with the VITEK® 2 and VITEK® 2 Compact Systems as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents. Levofloxacin has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.

Active in vitro and in clinical infections Streptococcus pneumoniae (including multi-drug resistant strains [MDRSP]) Streptococcus pyogenes

Active in vitro but clinical significance unknown β-hemolytic Streptococcus (Group C/F) B-hemolytic Streptococcus (Group G) Streptococcus agalactiae Streptococcus milleri Viridans group Streptococci

2. Indication(s) for use:

Active in vitro and in clinical infections Streptococcus pneumoniae (including multi-drug resistant strains [MDRSP]) Streptococcus pyogenes

Active in vitro but clinical significance unknown B-hemolytic Streptococcus (Group C/F) B-hemolytic Streptococcus (Group G) Streptococcus agalactiae Streptococcus milleri Viridans group Streptococci

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1. Special conditions for use statement(s):
  For prescription use only.

The ability of the VITEK 2 Streptococcus to detect resistance to Levofloxacin in S. pneumoniae and S. pyogenes is unknown because resistant organisms were not available at the time of comparative testing.

1. Special instrument requirements:
  For use with the VITEK® 2 and VITEK® 2 Compact Systems

I. Device Description:

VITEK 2StreptococcusLevofloxacin	EquivalentStandard MethodConcentration byEfficacy in µg/mL	FDA Interpretive CategoriesMIC in µg/mL:S	FDA Interpretive CategoriesMIC in µg/mL:I	FDA Interpretive CategoriesMIC in µg/mL:R
Levofloxacin	1, 2, 4, 16	≤ 2	4	≥ 8

The MIC ranges, interpretive criteria and equivalent concentrations are as follows:

S = Susceptible, I = Intermediate, R = Resistant.

J. Substantial Equivalence Information:

1. Predicate device name(s):

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VITEK 2 AST-GP Amoxicillin for S. pneumoniae

1. Predicate K number(s):
  K063597
1. Comparison with predicate:

Item	Device	Predicate
Intended Use	Determiningsusceptibility toantimicrobial agents	Same
Inoculation and testorganism	Isolated colonies ofStreptococcus species	Same
Instrument	Test are run on both theVITEK 2 and VITEK 2Compact Systems	Same
Test Card	The VITEK 2 card,including base broth	Same

Differences
Item	Device	Predicate
Test Method	Automated qualitativeantimicrobialsusceptibility test foruse with the VITEK® 2andVITEK® 2 CompactSystems todetermine the in vitrosusceptibility ofStreptococcusspecies.	Automated quantitativeantimicrobialsusceptibility test foruse with the VITEK® 2andVITEK® 2 CompactSystems todetermine the in vitrosusceptibility ofStreptococcusspecies.
Antibiotic	Levofloxacin-specificconcentrations	Amoxicillin-specificconcentrations
Reading algorithm	Unique to Levofloxacin	Unique to Amoxicillin

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

"Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA"

http://www.fda.gov/downloads/MedicalDevices/DeviceRegulationandGuidance/Guid anceDocuments/ucm071462.pdf

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Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically, Approved Standard -8th Edition, Document M7-A8.

Performance Standards for Antimicrobial Susceptibility Testing - 19th Informational Supplement, M100-S19.

L. Test Principle:

Automated growth based detection using attenuation of light measured by an optical scanner. The optics used in the systems use visible light to directly measure organism growth. Transmittance optics are based on an initial light reading of a well before significant growth has begun. Periodic light transmittance samplings of the same well measure organism growth by how much light is prevented from going through the well. The VITEK 2 System monitors the growth of each well in the card over a defined period of time. An interpretive call is made between 4 and 16 hours for a "rapid" read but may be extended to 18 hours in some instances. At the completion of the incubation cycle, a report is generated that contains the MIC value along with the interpretive category result for each antibiotic on the card. The VITEK 2 Streptococcus Levofloxacin has the following concentrations in the card: 1, 2, 4 and 16 ug/mL (equivalent standard method concentration by efficacy in ug/mL). The MIC result range for the VITEK 2 card is < 0.25 -> 16 ug/mL.

M. Performance Characteristics (if/when applicable):

1. Analytical performance:
- a. Precision/Reproducibility:

A reproducibility study was conducted at three external clinical sites. Ten Streptococcus species isolates were tested at each site and testing was performed in triplicate over three days with the VITEK 2 Streptococcus Levofloxacin card. The testing was performed using both the manual and the automated dilution methods. Testing was conducted on the VITEK 2 instrument.

All reproducibility isolates were inhibited at concentrations in the susceptible range for Levofloxacin and all MIC values were on-scale. Reproducibility was 100% with by both manual dilution and automated dilution.

b. Linearity/assay reportable range:
Not applicable

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c. Traceability, Stability, Expected values (controls, calibrators, or methods):
The recommended Streptococcus pneumonia QC organism was tested on every test occasion with the reference method and the VITEK 2 System. Ancillary quality control testing was also performed. Two gram-positive organisms were tested throughout comparative testing at each study site by the reference method only. This was done to perform further quality control of the broth microdilution panels using E. faecalis ATCC 29212 and S. aureus ATCC 29213 which have a QC range of 0.25 -2 ug/mL and 0.06-0.5 ug/mL respectively for Levofloxacin.

The reference method QC results were in range for every day tested. The VITEK 2 was tested a sufficient number of times to demonstrate that the system can produce acceptable QC results.

Quality Control was performed during the studies using both the auto-dilution and the manual method of diluting the organisms on the VITEK 2 System. Results demonstrated that methods were comparable.

Organism	Concentration(µg/mL)	Auto Dilution		Manual Dilution
		Reference	VITEK 2	Reference	VITEK 2
StreptococcuspneumoniaATCC 49619	≤0.125
	0.25*
	0.5*	164	208	166	212
	1*	48	4	48	2
AcceptableMIC range:0.5-2 µg/mL	2*
	4*
	8*
	16*
	≥32

Quality Control Results with the VITEK 2 System for Levofloxacin:

VITEK Card Result Range is < 0.25 -> 16

At least one Quality control organism was in control in the reference on all days. Quality Control results for the VITEK 2 System using either inoculation dilution method demonstrated that the VITEK 2 System could produce the expected quality control results.

A similar QC study was conducted to evaluate the VITEK 2 Compact System. Results were compared to the expected FDA/CLSI QC results. All results for the VITEK 2 Compact System were within the expected QC ranges 100% of the time.

Inoculum density control was monitored using the DensiChek2 instrument. This was standardized weekly with all results recorded and in the expected

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range.

d. Detection limit:
Not applicable.
e. Analytical specificity:
Not applicable.
f. Assay cut-off:
Not applicable
1. Comparison studies:
- a. Method comparison with predicate device:

Performance was established through a clinical study which was conducted at four external study sites. A total of 1338 clinical isolates were tested by VITEK® 2 Streptococcus Levofloxacin with the VITEK® 2 System. The majority of the isolates were recently isolated from clinical specimens and the growth rate was 100%. Two hundred and nine of the 1338 clinical isolates tested were stock isolates (15.6%). A challenge set consisting of 207 isolates was evaluated with VITEK® 2 Streptococcus Levofloxacin panel at one external site.

Testing of clinical isolates was performed using the automated method of inoculation and the challenge organisms were tested with both the manual dilution and automatic dilution. Each isolate was tested by the VITEK 2 Levofloxacin Streptococcus panel and the CLSI broth microdilution reference method. The inoculum was prepared with direct colony suspension. A comparison was provided to the reference method with the following agreement. Thirty-two minor errors were seen.

	EATot	EAN	EA%	EvalEATot	EvalEAN	EvalEA%	CAN	CA%	#R	#vmj	#maj	#min
OrganismGroup
Streptococcus species
CLINICAL	1338	1323	98.9	1152	1143	99.2	1307	97.7	19	0	0	31
CHALLENGE	207	207	100	190	190	100	206	99.5	0	0	0	1
COMBINED(CLINICALANDCHALLENGE)	1545	1530	99.0	1342	1333	99.3	1513	97.9	19	0	0	32

AutoDilution

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EA-Essential Agreement CA-Category Agreement maj-major discrepancies vmj-very major discrepancies min-minor discrepancies

A CA of 97.7%/99.5 % was observed for clinical/challenge isolates, respectively. An EA of 98.9%/100 % was observed for clinical/challenge isolates, respectively. However, a right shift in MIC occurred around the intermediate breakpoint.

No major or very major categorical errors occurred but a total of 32 (2.1%) minor categorical errors were seen. Of note is that all of the minor errors seen shifted the interpretation from "Susceptible" by the reference method to "Intermediate" by VITEK. Those minor errors were as follows: 17 were with S. pyogenes, 6 were with S. agalactiae, 6 were with S. mitis/oralis, 2 were with S. dysgalactiae and 1 was with S. oralis. No Levofloxacin-resistant S. pneumoniae or S. pyogenes isolates were tested in this evaluation.

Performance of the VITEK® 2 and the VITEK® 2 Compact was also evaluated with the same 207 challenge organisms using the manual dilution method. Results from those two studies showed CA of 99.5% and 98.1% and EA of 100% and 98.6% respectively for VITEK® 2 and the VITEK® 2 Compact.

All ranges were acceptable as defined in the AST Guidance Document.

b. Matrix comparison:
Not Applicable
1. Clinical Studies:
- a. Clinical Sensitivity:

Not Applicable

b. Clinical specificity:
Not Applicable
c. Other clinical supportive data (when a. and b. are not applicable):
Not Applicable
1. Clinical cut-off:
  Not Applicable

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5. Expected values/Reference range:

FDA Interpretive criteria for Levofloxacin when testing Streptococcus species, including S. pneumoniae are:

S= ≤ 2 μg/mL, I = 4 μg/mL, R= ≥8 μg/mL

N. Proposed Labeling:

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

O. Conclusion:

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

Regulation Number and Section

§ 866.1645 Fully automated short-term incubation cycle antimicrobial susceptibility system.

(a)
Identification. A fully automated short-term incubation cycle antimicrobial susceptibility system is a device that incorporates concentrations of antimicrobial agents into a system for the purpose of determining in vitro susceptibility of bacterial pathogens isolated from clinical specimens. Test results obtained from short-term (less than 16 hours) incubation are used to determine the antimicrobial agent of choice to treat bacterial diseases.(b)
Classification. Class II (special controls). The special control for this device is FDA's guidance document entitled “Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA.”