MTS Tetracycline 0.016 - 256 ug/mL

K183140 · Liofilchem s.r.l. · JWY · Jan 11, 2019 · Microbiology

Device Facts

• Record ID: K183140
• Device Name: MTS Tetracycline 0.016 - 256 ug/mL
• Applicant: Liofilchem s.r.l.
• Product Code: JWY · Microbiology
• Decision Date: Jan 11, 2019
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 866.1640
• Device Class: Class 2

Indications for Use

The Liofilchem MTS (MIC Test Strip) Tetracycline 0.016-256 µg/mL is a quantitative method intended for the in vitro determination of antimicrobial susceptibility of bacteria. MTS consists of specialized paper impregnated with a pre-defined concentration gradient of an antimicrobial agent, which is used to determine the minimum inhibitory concentration (MIC) in µg/mL of antimicrobial agents against bacteria as tested on agar media using overnight incubation and manual reading procedures. The MTS Tetracycline at concentrations of 0.016-256 µg/mL should be interpreted at 16-20 hours of incubation. Tetracycline has been shown to be active both clinically and in vitro against these bacterial species according to the FDA drug approved label: Staphylococcus aureus, Acinetobacter baumannii, Escherichia coli, Klebsiella aerogenes, Klebsiella oxytoca, Klebsiella pneumonia

Device Story

MTS Tetracycline is a manual, growth-based antimicrobial susceptibility test. It consists of a paper strip impregnated with a predefined exponential concentration gradient of tetracycline (0.016-256 µg/mL). The strip is applied to an inoculated Mueller Hinton agar plate. After 16-20 hours of incubation, a symmetrical inhibition ellipse forms around the strip. The clinician manually reads the MIC value at the point where the ellipse intersects the strip. The device provides quantitative MIC results, which are used by healthcare providers to determine the susceptibility of bacterial isolates to tetracycline, aiding in the selection of appropriate antibiotic therapy. The device is intended for use in clinical laboratory settings.

Clinical Evidence

No clinical data provided; bench testing only.

Technological Characteristics

Specialized paper strip impregnated with a predefined exponential concentration gradient of tetracycline (0.016-256 µg/mL). Manual reading of inhibition ellipse on Mueller Hinton agar. Incubation at 35 ± 2°C for 16-20 hours. Standalone, non-electronic, manual diagnostic test.

Indications for Use

Indicated for in vitro determination of antimicrobial susceptibility of non-fastidious Gram-negative organisms (A. baumannii, E. coli, K. aerogenes, K. oxytoca, K. pneumoniae) and S. aureus. For prescription use.

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.

Submission Summary (Full Text)

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510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY

A. 510(k) Number:
K183140

B. Purpose for Submission:
To obtain a substantial equivalence determination for Tetracycline at concentrations of 0.016-256 µg/mL for susceptibility testing of non-fastidious Gram-negative organisms and Staphylococcus aureus

C. Measurand:
Tetracycline 0.016-256 µg/mL

D. Type of Test:
Quantitative Antimicrobial Susceptibility Test growth-based detection

E. Applicant:
Liofilchem s.r.l.

F. Proprietary and Established Names:
MTS Tetracycline 0.016-256 µg/mL

G. Regulatory Information:
1. Regulation section:
866.1640 Antimicrobial Susceptibility Test Powder
2. Classification:
II
3. Product code:
JWY - Manual Antimicrobial Susceptibility Test Systems
4. Panel:

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83 – Microbiology

H. Intended Use:

1. Intended use(s):

The Liofilchem MTS (MIC Test Strip) Tetracycline 0.016-256 µg/mL is a quantitative method intended for the in vitro determination of antimicrobial susceptibility of bacteria. MTS consists of specialized paper impregnated with a pre-defined concentration gradient of an antimicrobial agent, which is used to determine the minimum inhibitory concentration (MIC) in µg/mL of antimicrobial agents against bacteria as tested on agar media using overnight incubation and manual reading procedures.

The MTS Tetracycline at concentrations of 0.016-256 µg/mL should be interpreted at 16-20 hours of incubation.

Tetracycline has been shown to be active both clinically and in vitro against these bacterial species according to the FDA drug approved label:

Staphylococcus aureus
Acinetobacter baumannii
Escherichia coli
Klebsiella aerogenes
Klebsiella oxytoca
Klebsiella pneumonia

2. Indication(s) for use:

Same as Intended Use

3. Special conditions for use statement(s):

- For prescription use
- Liofilchem MIC Test Strip (MTS) Tetracycline MIC values tended to be in exact agreement or at least one doubling dilution higher when testing A. baumannii, and Enterobacteriaceae (specifically when testing K. oxytoca and K. pneumoniae) compared to the CLSI reference broth microdilution.
- The safety and efficacy of tetracycline in treating clinical infections due to species of Enterobacteriaceae other than K. aerogenes, K. pneumoniae, K. oxytoca, and E. coli, and Staphylococcus species other than S. aureus may or may not have been established in adequate and well-controlled clinical trials. The clinical significance of susceptibility information in such instances is unknown.

4. Special instrument requirements:

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Manual reading only

I. Device Description:

The Tetracycline MIC Test Strip (MTS) consists of specialized paper impregnated with a predefined concentration gradient of Tetracycline across 15 two-fold dilutions similar to dilutions used by conventional MIC methods. One side of the strip is labelled with the Tetracycline code (TE) and the MIC reading scale in $\mu \mathrm{g} / \mathrm{mL}$. When the MIC Test Strip is applied onto an inoculated agar surface, the preformed exponential gradient of antimicrobial agent is immediately transferred to the agar matrix. After 16-20 hours incubation, a symmetrical inhibition ellipse centered along the strip is formed. The MIC is read directly from the scale in terms of $\mu \mathrm{g} / \mathrm{mL}$ at the point where the edge of the inhibition ellipse intersects the MIC Test Strip. Since MTS strip generates MIC values which fall between two-fold dilutions for interpretation, the MIC value read is recorded to the next two-fold dilution value.

J. Substantial Equivalence Information:

1. Predicate device name(s):

Liofilchem MTS, vancomycin

2. Predicate $510(\mathbf{k})$ number(s):

K153687

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# 3. Comparison with predicate:

Table 1: Comparison with the Predicate Device

| Similarities | | |
| --- | --- | --- |
| Item | Device Liofilchem MTS, Tetracycline (K183140) | Predicate Liofilchem MTS, Vancomycin (K153687) |
| Media | Mueller Hinton agar | Same |
| Inoculation | Isolated colonies from culture in suspension equivalent to 0.5 McFarland. Inoculum is applied manually using the manual plate inoculation method or plate rotator for even distribution of inoculum | Same |
| Result | MIC | Same |
| Differences | | |
| --- | --- | --- |
| Item | Device Liofilchem MTS, Tetracycline (K183140) | Predicate Liofilchem MTS, Vancomycin (K153687) |
| Intended Use | Quantitative susceptibility to antimicrobial agents against Gram-negative and S. aureus | Quantitative susceptibility to antimicrobial agents to Gram-positive organisms |
| Antibiotic | Tetracycline code (TE) | Vancomycin code (VA) |
| Reading | Manual; the point where the edge of inhibition ellipse intersects the MIC Test Strip; interpret the MIC as 80% inhibition when trailing is seen | Manual; the point where the edge of inhibition ellipse intersects the MIC Test Strip; interpret the MIC at 100% inhibition |
| Incubation | 35 ± 2°C for 16 – 20 hours | 35 ± 2°C for 24 hours |

# K. Standard/Guidance Document Referenced:

- Guidance for Industry and FDA - Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems - August 28, 2009.
- CLSI M07-A10 "Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically; Approved Standard, Tenth Edition January 2015".
- CLSI M100-S26 "Performance Standards for Antimicrobial Susceptibility Testing; Twenty-Fifth Informational Supplement, January 2016".

# L. Test Principle:

MTS are made of specialized paper impregnated with a predefined concentration gradient of antibiotic, across 15 two-fold dilutions similar to dilutions used by conventional MIC methods. When the MIC Test Strip is applied onto an inoculated agar surface, the preformed exponential gradient of antimicrobial agent is immediately transferred to the agar matrix. After 16-20 hours incubation, a symmetrical inhibition ellipse centered along the strip is

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formed. The MIC is read directly from the scale in terms of $\mu \mathrm{g} / \mathrm{mL}$ at the point where the edge of the inhibition ellipse intersects the strip MIC Test Strip.

Growth along the entire gradient (i.e., no inhibition ellipse) indicates that the MIC value is greater than or equal to $(\geq)$ the highest value on the scale. An inhibition ellipse that intersects below the lower end of the scale is read as less than $(<)$ the lowest value. An MIC of 0.125 $\mu \mathrm{g} / \mathrm{mL}$ is considered to be the same as $0.12 \mu \mathrm{g} / \mathrm{mL}$ for reporting purposes. Given that tetracycline is a bacteriostatic drug, the ellipse should be interpreted at $80\%$ inhibition when trailing is observed.

An MTS MIC value which falls between standard two-fold dilutions must be rounded up to the next standard upper two-fold value before categorization.

## M. Performance Characteristics:

### 1. Analytical performance:

#### a. Precision/Reproducibility:

Reproducibility testing was conducted at three sites using ten Gram-negative and ten Gram-positive organisms. Each isolate was tested in triplicate over three days for a total of 270 data points. The mode of MIC values was determined for each isolate and the reproducibility was calculated based on the number of MIC values that fell within $\pm 1$ doubling dilution of the mode. The Gram-negative reproducibility panel included three *E. coli*, three *K. pneumoniae*, one *K. oxytoca*, one *K. aerogenes*, and two *A. baumannii* isolates and the Gram-positive panel included five methicillin-resistant *S. aureus* five methicillin-susceptible *S. aureus* isolates. All MIC results were on scale. The testing resulted in overall reproducibility of greater than $95\%$ for both Gram-negative and Gram-positive isolates.

The results were acceptable.

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

Not applicable

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

##### Quality Control (QC) Testing:

The CLSI recommended QC strains, namely *E. coli* ATCC 25922 and *P. aeruginosa* ATCC 27853 for Gram-negative organisms and *S. aureus* ATCC 29213 and *E. faecalis* ATCC 29212 for Gram-positive organisms were tested a sufficient number of times (i.e., at least 20/site) at each testing site using both MTS and reference methods. The results are summarized in Table 2 below. The quality control results are acceptable.

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Table 2: Tetracycline MTS QC Results

| Organism | Concentration (μg/mL) | Reference | MTS |
| --- | --- | --- | --- |
| E. coli | 0.25 | | |
| ATCC 25922 | 0.5 | 27 | 12 |
| | 1 | 34 | 43 |
| Expected Result: | 2 | | 6 |
| 0.5 - 2 μg/mL | 4 | | |
| P. aeruginosa | 4 | | |
| ATCC 27853 | 8 | 42 | 12 |
| | 16 | 19 | 42 |
| Expected Result: | 32 | | 7 |
| 8 - 32 μg/mL | 64 | | |
| S. aureus | 0.06 | | |
| ATCC 29213 | 0.12 | 3 | 4 |
| | 0.25 | 47 | 41 |
| Expected Result: | 0.5 | 10 | 15 |
| 0.12 - 1 μg/mL | 1 | | |
| | 2 | | |
| E. faecalis | 4 | | |
| ATCC 29212 | 8 | 20 | 13 |
| | 16 | 35 | 43 |
| Expected Result: | 32 | 5 | 4 |
| 8 - 32 μg/mL | 64 | | |

Inoculum Density Check:
The inoculum was prepared to achieve turbidity equivalent to a 0.5 McFarland standard. Colony counts were performed periodically at each site for all QC replicates, from at least one replicate of each reproducibility isolate on each of the three days of testing, and from a minimum of 10% of the clinical and challenge strains tested. Inoculum density checks were performed and the colony counts obtained for each isolate were within the recommended range of approximately 1x 10⁸ CFU/mL.

Purity Checks:
Purity checks were performed on all isolates following MTS inoculation. All isolates were pure in both the broth microdilution reference panels and the MTS agar plates.

Growth Failure Rate:
None of the isolates in the study failed to grow with the Tetracycline MTS.

d. Detection limit:
Not Applicable

e. Analytical specificity:

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Not Applicable

f. Assay cut-off:

Not Applicable

2. Comparison studies:

a. Method comparison with predicate device:

The MTS, Tetracycline was evaluated at three sites located within the United States. Each clinical isolate was tested one time by MTS Tetracycline and the reference method using the same initial standardized suspension. A total of 315 clinical *S. aureus* isolates of which 79.7% were tested within six months of isolation (contemporary isolates) and 315 non-fastidious Gram-negative isolates were tested of which 65.7% were tested within six months of isolation. The Gram-positive organisms included 156 methicillin-susceptible *S. aureus* and 159 methicillin-resistant *S. aureus*. The Gram-negative organisms included 120 *E. coli*, 30 *K. aerogenes*, 30 *K. oxytoca*, 75 *K. pneumoniae*, and 60 *A. baumannii* isolates.

Challenge testing was performed at one internal site. A total of 75 Gram-positive and 78 Gram-negative challenge isolates were tested. The Gram-positive organisms included one methicillin-susceptible *S. aureus* and 74 methicillin-resistant *S. aureus*. The Gram-negative organisms included 19 *E. coli*, 15 *K. aerogenes*, 15 *K. oxytoca*, 19 *K. pneumoniae*, and 10 *A. baumannii* isolates.

Results obtained with the MTS Tetracycline were compared to results obtained with the CLSI broth microdilution reference panel. The reference panel contained two-fold serial dilutions of Tetracycline with a range of 0.016 – 256 µg/mL. The testing conditions for the reference method were consistent with CLSI guidelines as listed in the CLSI document M07-A10. Isolated colonies from an overnight blood agar plate were suspended in saline to achieve a 0.5 McFarland standard turbidity (approximately 10⁸ CFU/mL). Testing conditions consisted of incubation of the inoculated Mueller Hinton agar plates in an inverted position at 35°C ± 2° for 16-20 hours. At the end of incubation, the MIC value determined at 80% inhibition of growth along the strip was compared to MIC results obtained with the reference method. Visual aids were provided in reading guides to each laboratory to assist in interpretation.

The performance for the total (combined clinical and challenge) 390 *S. aureus*, 323 *Enterobacteriaceae*, and 70 *A. baumannii* isolates is summarized in Table 3 and 4 below.

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Table 3: Overall Performance of S. aureus Clinical and Challenge Isolates

| Tetracycline | EA Tot | EA N | EA % | Eval. EA Tot | Eval. EA N | Eval. EA% | CA N | CA% | #R | min | maj | vmj |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| S. aureus (MSSA+MRSA) Clinical | 315 | 315 | 100 | 315 | 315 | 100 | 313 | 99.4 | 15 | 2 | 0 | 0 |
| Challenge | 75 | 75 | 100 | 73 | 73 | 100 | 74 | 98.7 | 25 | 1 | 0 | 0 |
| Combined | 390 | 390 | 100 | 388 | 388 | 100 | 387 | 99.2 | 40 | 3 | 0 | 0 |

Table 4: Overall Performance of Gram-negative Clinical and Challenge Isolates

| Tetracycline | EA Tot | EA N | EA % | Eval. EA Tot | Eval. EA N | Eval. EA% | CA N | CA% | #R | min | maj | vmj |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Enterobacteriaceae (all) Clinical | 255 | 255 | 100 | 227 | 227 | 100 | 249 | 97.6 | 55 | 6 | 0 | 0 |
| Challenge | 68 | 68 | 100 | 43 | 43 | 100 | 67 | 98.5 | 41 | 1 | 0 | 0 |
| Combined | 323 | 323 | 100 | 270 | 270 | 100 | 316 | 97.8 | 96 | 7 | 0 | 0 |
| | | | | | | | | | | | | |
| A. baumannii Clinical | 60 | 57 | 95.0 | 34 | 31 | 91.2 | 57 | 95.0 | 32 | 3 | 0 | 0 |
| Challenge | 10 | 10 | 100 | 3 | 3 | 100 | 10 | 100 | 10 | 0 | 0 | 0 |
| Combined | 70 | 67 | 95.7 | 37 | 34 | 91.9 | 67 | 95.7 | 42 | 3 | 0 | 0 |

EA – Essential agreement
CA – Category agreement
EVAL – Evaluable isolates
R – Resistant isolates

maj – Major errors
vmj – Very major errors
min – Minor errors

Essential Agreement (EA) is when the Liofilchem MIC Test Strip (MTS) results agree exactly or within one doubling dilution of the reference broth microdilution results. Category Agreement (CA) is when the Liofilchem MIC Test Strip (MTS) result interpretation agrees exactly with the reference broth microdilution result interpretation.

The overall performance of S. aureus (both MRSA and MSSA) isolates is acceptable with 100% EA and 99.2% CA. There were no major or very major errors.

The overall performance of all Enterobacteriaceae isolates is acceptable with 100% EA and 97.8% CA. In addition, the performance for each Gram-negative organism was evaluated separately and results for each demonstrated >90% EA and >90% CA with no major or very major errors and was, therefore, deemed acceptable. In addition, the overall performance of A. baumannii isolates was acceptable with 95.7% EA and 95.7% CA.

## Trending:

Trending was assessed separately for S. aureus and Gram-negative organisms using data for challenge and clinical isolates (Tables 5 and 6). Trending was assessed using current

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trending review practices (i.e., $\geq 30\%$ difference between higher and lower dilution readings). No significant trending was observed for S. aureus; however, trending was observed for A. baumannii, K. oxytoca, and K. pneumoniae which tended to be in exact agreement or higher when compared to the reference method. The difference between higher and lower dilutions for this organism was $>30\%$ . Given the observed trending, the following was included in the labeling:

- Liofilchem MIC Test Strip (MTS) Tetracycline MIC values tended to be in exact agreement or at least one doubling dilution higher when testing A. baumannii, and Enterobacteriaceae (specifically when testing K. oxytoca and K. pneumoniae) compared to the CLSI reference broth microdilution.

Table 5. Trending Analysis for S. aureus

| Total | ≥1 dil. lower | Exact | ≥1 dil. higher |
| --- | --- | --- | --- |
| S. aureus (MSSA+MRSA)a | | | |
| 390 | 81 | 277 | 32 |
| | (20.77%) | (71.03%) | (8.21%) |

${}^{a}$ Difference between the higher and lower dilutions for S. aureus is: -12.56%; 95% C.I. (-17.46% to - 7.68%)

Table 6: Tetracycline Trending Analysis for Gram-negative organisms

| Total | ≥1 dil. lower | Exact | ≥1 dil. higher |
| --- | --- | --- | --- |
| A. baumannii | | | |
| 38 | 1 | 12 | 25 |
| | (2.63%) | (31.58%) | (65.79%) |
| E. coli | | | |
| 115 | 13 | 67 | 35 |
| | (11.30%) | (58.26%) | (30.43%) |
| K. aerogenes | | | |
| 42 | 1 | 31 | 10 |
| | (2.38%) | (73.81%) | (23.81%) |
| K. oxytocad | | | |
| 45 | 2 | 23 | 20 |
| | (4.44%) | (51.11%) | (44.44%) |
| K. pneumoniae | | | |
| 82 | 2 | 40 | 40 |
| | (2.44%) | (48.78%) | (48.78%) |
| All Enterobacteriaceae | | | |
| 284 | 18 | 161 | 105 |
| | (6.34%) | (56.69%) | (36.97%) |

${}^{a}$ Difference between the higher and lower dilutions for A. baumannii is: 63.16%; 95% C.I. (43.90% to 76.34%)
${}^{b}$ Difference between the higher and lower dilutions for E. coli is: 19.13%; 95% C.I. (8.70% to 29.16%)
${}^{c}$ Difference between the higher and lower dilutions for K. aerogenes is: 21.43%; 95% C.I. (7.09% to 36.28%)
${}^{d}$ Difference between the higher and lower dilutions for $K$ . oxytoca is: ${40.00}\% ;{95}\%$ C.I. (22.96% to 54.74%)
${}^{e}$ Difference between the higher and lower dilutions for $K$ . pneumoniae is: ${46.34}\% ;{95}\%$ C.I. (34.22% to 57.12%)

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${}^{a}$ Difference between the higher and lower dilutions for Enterobacteriaceae is: ${30.63}\% ;{95}\%$ C.I. (24.22% to 36.83%)

b. Matrix comparison:

Not Applicable

3. 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

4. Clinical cut-off:

Not Applicable

5. Expected values/Reference range:

The FDA susceptibility interpretive criteria for Tetracycline are as listed in Table 7.

Table 7: FDA Recognized Interpretive Criteria for Tetracycline (μg/mL)

| Organisms | S | I | R |
| --- | --- | --- | --- |
| Enterobacteriaceae | ≤4 | 8 | ≥16 |
| Acinetobacter spp. | ≤4 | 8 | ≥16 |
| Staphylococcus spp. | ≤4 | 8 | ≥16 |

# N. Proposed Labeling:

The labeling supports the finding of substantial equivalence for this device.

# O. Conclusion:

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