← Product Code [JSO](/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO) · K100589

# MRSA SELECT - SKIN AND SOFT TISSUE WOUND SPECIMENS (K100589)

_Bio-Rad · JSO · Oct 29, 2010 · Microbiology · SESE_

**Canonical URL:** https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO/K100589

## Device Facts

- **Applicant:** Bio-Rad
- **Product Code:** [JSO](/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO.md)
- **Decision Date:** Oct 29, 2010
- **Decision:** SESE
- **Submission Type:** Traditional
- **Regulation:** 21 CFR 866.1700
- **Device Class:** Class 2
- **Review Panel:** Microbiology

## Indications for Use

MRSASelect™ is a selective and differential chromogenic medium for the qualitative detection of methicillin resistant Staphylococcus aureus (MRSA) from skin and soft-tissue wound specimens. The medium is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA from patients with skin and soft-tissue infections. Concomitant cultures and susceptibility testing are necessary for all skin and soft-tissue wound specimens. MRSASelect™ is not intended to guide, or monitor treatment for MRSA infection, or provides results of susceptibility to methicillin. Results can be interpreted after 18 to 28 hours incubation.

## Device Story

MRSASelect is a selective/differential chromogenic culture medium for direct detection of MRSA from skin and soft-tissue wound specimens. Medium incorporates antifungal/antibiotic mixture and optimized salt concentration to inhibit non-MRSA growth (yeast, Gram-negative/positive bacteria). Identification relies on cleavage of chromogenic substrate by S. aureus enzymatic activity, producing pink colonies. Used in clinical microbiology laboratories; processed manually by technicians. Plates incubated 18-28 hours at 35-37°C. Results interpreted visually by laboratory personnel. Output aids clinicians in identifying MRSA in wound infections; requires concomitant culture/susceptibility testing. Does not monitor treatment or provide methicillin susceptibility results.

## Clinical Evidence

Clinical study of 943 skin and soft-tissue wound samples across four US laboratories. Compared MRSASelect to routine culture (TSA/TSB) with confirmatory testing (Gram stain, Pastorex Staph Plus, mecA/Cefoxitin disk). Results: sensitivity 91.7% (95% CI: 87.3-94.7%), specificity 99.4% (95% CI: 98.5-99.8%). Analytical sensitivity (102 strains) was 97% after 24 hours. Reproducibility was 100%.

## Technological Characteristics

Selective/differential chromogenic agar medium. Contains antibiotic/antifungal mixture and optimized salt concentration. Manual visual readout. Incubation 18-28 hours at 35-37°C. No electronic components or software.

## Regulatory Identification

A culture medium for antimicrobial susceptibility tests is a device intended for medical purposes that consists of any medium capable of supporting the growth of many of the bacterial pathogens that are subject to antimicrobial susceptibility tests. The medium should be free of components known to be antagonistic to the common agents for which susceptibility tests are performed in the treatment of disease.

## Predicate Devices

- MRSASelect (k081212)

## Submission Summary (Full Text)

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

A. 510(k) Number:
k100589

B. Purpose for Submission:
To obtain substantial equivalent determination for a premarket notification for MRSASelect™ for direct detection of MRSA from skin and soft-tissue wound specimens

C. Measurand:
Methicillin resistant Staphylococcus aureus (MRSA)

D. Type of Test:
Direct detection of MRSA from skin and soft-tissue wound specimens using specific chromogenic substrates and selective antifungal/antimicrobial mixture

E. Applicant:
Bio-Rad

F. Proprietary and Established Names:
MRSA Select

G. Regulatory Information:
1. Regulation section:
CFR 866.1700
2. Classification:
II
3. Product code:
JSO: Culture media, Antimicrobial susceptibility test, excluding Mueller Hinton Agar

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4. Panel:

83 Microbiology

H. Intended Use:

1. Intended use(s):

MRSASelect™ is a selective and differential chromogenic medium for the qualitative detection of methicillin resistant Staphylococcus aureus (MRSA) from skin and soft-tissue wound specimens. The medium is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA from patients with skin and soft-tissue infections. Concomitant cultures and susceptibility testing are necessary for all skin and soft-tissue wound specimens. MRSASelect™ is not intended to guide, or monitor treatment for MRSA infection, or provides results of susceptibility to methicillin. Results can be interpreted after 18 to 28 hours incubation.

2. Indication(s) for use:

MRSASelect™ is a selective and differential chromogenic medium for the qualitative detection of methicillin resistant Staphylococcus aureus (MRSA) from skin and soft-tissue wound specimens. The medium is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA from patients with skin and soft-tissue infections. Concomitant cultures and susceptibility testing are necessary for all skin and soft-tissue wound specimens. MRSASelect™ is not intended to guide, or monitor treatment for MRSA infection, or provides results of susceptibility to methicillin. Results can be interpreted after 18 to 28 hours incubation.

3. Special conditions for use statement(s):

Prescription use only

4. Special instrument requirements:

Not applicable

I. Device Description:

MRSASelect is a selective and differential chromogenic medium for the qualitative detection of MRSA from skin and soft-tissue wound specimens. Selective antifungal/antibiotics mixture is incorporated in the medium to inhibit the growth of yeasts, Gram negative and Gram positive bacteria except MRSA. Identification is based on the cleavage of a chromogenic substrate by a specific enzymatic activity of Staphylococcus aureus, leading to a strong pink coloration of the Staphylococcus

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aureus colonies. Plates may be read within 18-28 hours incubation.

## J. Substantial Equivalence Information:

1. Predicate device name(s):

MRSASelect

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

k081212

3. Comparison with predicate:

|  Similarities  |   |   |
| --- | --- | --- |
|  Item | Device | Predicate  |
|  Intended Use | For detection of MRSA | For detection of MRSA  |
|  Reporting | MRSA | MRSA  |
|  Reading | Manual | Manual  |
|  Test methodology | selective chromogenic agar | selective chromogenic agar  |
|  Differences  |   |   |
| --- | --- | --- |
|  Item | Device | Predicate  |
|  Intended Use | In conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA from patients with skin and soft-tissue infections. | Screen for the detection of colonization of methicillin resistant Staphylococcus aureus (MRSA) to aid in the prevention and control of MRSA infections in healthcare settings.  |
|  Inoculum | Direct | Direct and Indirect (saline)  |
|  Specimen sample | Skin and soft tissue | Nares  |

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

Clinical and Laboratory Standard Institute (CLSI) M100-S20 Performance Standards for Antimicrobial Susceptibility Testing; CLSI M29-A2 Protection of Laboratory Workers from Occupational Acquired Infections; CLSI M40-A Quality Control of Microbiological Transport Systems; Approved Standard

## L. Test Principle:

MRSASelect is a selective medium for the detection and direct identification of MRSA. The selectivity of this medium is based on the presence of an antibiotic/antifungal mixture and an optimized salt concentration that inhibits the growth of yeast and the majority of Gram negative and Gram positive bacteria with the exception of methicillin-resistant staphylococci. Identification is based on the cleavage of a chromogenic substrate by a specific enzymatic activity of

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Staphylococcus aureus, leading to a strong pink coloration of the Staphylococcus aureus colonies.

## M. Performance Characteristics (if/when applicable):

### 1. Analytical performance:

#### a. Precision/Reproducibility:

Reproducibility Testing was done at three sites in triplicates for three days with three lots. The study included two strains each for MRSA, MSSA and *S. epidermidis*. *S. aureus* ATCC 43300 was also tested. It was performed at concentrations of $10^{6}$ CFU/mL for MRSA, and $10^{8}$ CFU/mL for non-MRSA. Reproducibility was >95%.

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

Not applicable

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

Negative Control

*S. aureus* ATCC 25923 at a concentration of $10^{4} - 10^{5}$ CFU/plate

Positive Control

*S. aureus* ATCC 43300 at a concentration of $10^{3} - 10^{4}$ CFU/plate

|  Test Strain | Expected Results after 24 hours at 35-37°C  |
| --- | --- |
|  *S. aureus* ATCC 25923 | No Growth  |
|  *S. aureus* ATCC 43300 | Growth – small pink colonies  |

QC was performed at each testing site on more than three lots. The testing followed the recommendations of the QC strains listed in the package insert and there were no product failures.

#### d. Detection limit:

The LoD study was performed on two well characterized MRSA strains, at six serial dilutions, per strain, per dilution, on two MRSA Select plates and by two operators. The results demonstrated the LoD of $10^{3}$ CFU/mL.

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S. aureus ATCC 43300

|  Inoculum* (CFU/mL) | MRSASelect  |   |   |   |   |   |   |   |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   |  18 Hours |   |   |   | 28 Hours  |   |   |   |
|   |  CFU | Color | CFU | Color | CFU | Color | CFU | Color  |
|  9.13 x 10^{6} | >100 | Pink | >100 | Pink | >100 | Pink | >100 | Pink  |
|  8.40 x 10^{5} | >100 | Pink | >100 | Pink | >100 | Pink | >100 | Pink  |
|  7.53 x 10^{4} | >100 | Pink | >100 | Pink | >100 | Pink | >100 | Pink  |
|  9.18 x 10^{3} | 3/10 | Pink | 29/39 | Pink | 4/15 | Pink | 35/49 | Pink  |
|  7.12 x 10^{2} | 2/2 | Pink | 5/1 | Pink | 2/3 | Pink | 5/3 | Pink  |
|  7.50 x 10^{1} | 0/1 | Pink | 0/0 | Pink | 1/1 | Pink | 0/0 | Pink  |

* Average CFU/mL obtained on Blood Agar Plate

S. aureus NRS660

|  Inoculum* (CFU/mL) | MRSASelect  |   |   |   |   |   |   |   |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
|   |  18 Hours |   |   |   | 28 Hours  |   |   |   |
|   |  CFU | Color | CFU | Color | CFU | Color | CFU | Color  |
|  1.47 x 10^{7} | >100 | Pink | >100 | Pink | >100 | Pink | >100 | Pink  |
|  1.27 x 10^{6} | >100 | Pink | >100 | Pink | >100 | Pink | >100 | Pink  |
|  1.52 x 10^{5} | >100 | Pink | >100 | Pink | >100 | Pink | >100 | Pink  |
|  1.42 x 10^{4} | 50/100 | Pink | 50/100 | Pink | 103/161 | Pink | 102/180 | Pink  |
|  1.46 x 10^{3} | 10/12 | Pink | 11/25 | Pink | 10/13 | Pink | 11/27 | Pink  |
|  1.42 x 10^{2} | 0/0 | Pink | 1/3 | Pink | 0/0 | Pink | 3/1 | Pink  |

* Average CFU/mL obtained on Blood Agar Plate

## Analytical reactivity

The study included 102 well characterized MRSA from the Network on Antimicrobial Resistance in *Staph aureus* (NARSA) collection, tested at concentrations $10^{3} - 10^{4}\mathrm{CFU / mL}$. They were USA100, 200, 300, 500, 600, 700, 800, and 1000. The USA300-0114 (NRS 384) was also tested.

Results demonstrated that strains NRS722, 727, and 730 produce white colonies at 18hrs, but pink colonies at 24 hrs; NRS676, and 745 produce pink colonies at $\geq 10^{5}$ CFU/mL, higher than the LoD of $10^{3}$ CFU/mL.

e. Analytical specificity:

## Interference Study

The interference study included blood, pus and non-prescription debriding agents. The debriding agents tested were $1\mathrm{U} / \mathrm{g}$ fibrinolysin and $666\mathrm{U} / \mathrm{g}$ desoxyribobnuclease, Papain+urea (1%), and Papain+urea (5%). No

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interference observed.

Topical compounds commonly used in wound care were also tested. The following compounds demonstrated inhibitory effect on the recovery of MRSA:

- Bactine- Benzalkonium chloride 0.13%, Lidocaine hydrochloride 2.5%
- Betadine (liquid) - Povidone-iodine 10%
- Iodine Tincture (liquid) - Iodine 2%
- Biseptine (liquid) - Chlorhexidine Gluconate 0.25%, Benzalkonium chloride 0.025%
- Sodium hypochlorite (liquid)
- StaphAseptic (ointment) - Benzethonium Chloride 0.2%, Lidocaine HCl 2.5%
- Silver chloride (gel)
- Neosporin
- Polysporin

This information will be added to the Package Insert in Limitations section (item# i).

## Cross Reactivity Study

There were 35 non-staphylococcal isolates tested at concentration of ≥10⁶ CFU/mL in the SSTI premarket application. No pink colonies observed.

The isolates whose performance resulted in a limitation statement for the nasal submission was also included in this submission (i.e. faint pink colonies for some S. epidermidis, pink coloration for some Gram negative rods, and Acinetobacter); pinpoint white colonies were observed for Corynebacterium jeikeium and Candida tropicalis.

## Mixed infection study

A mixed infection study was performed to demonstrate the performance of the MRSA Select if mixed infection was encountered in wound or SSTI samples. S. aureus ATCC43300 at LoD (i.e. 10³ CFU/mL), oxacillin resistant S. epidermidis and K. pneumoniae at increasing concentrations up to 10⁶ CFU/mL each were tested. No interference was observed.

f. Assay cut-off:

Not applicable

2. Comparison studies:

a. Method comparison with predicate device:

Not applicable. Compared to Standard Reference Method

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b. Matrix comparison:

Not applicable

3. Clinical studies:

a. Clinical Sensitivity:

The MRSASelect™ culture media was evaluated at four clinical sites which included testing of 943 specimens. All the samples were inoculated directly onto the following media:

- Trypticase Soy Agar (TSA) with 5% Sheep Blood
- MRSASelect
- Tryptic Soy Broth (TSB) with 6.5% NaCl

MRSASelect plates, TSA, and TSB were incubated at 35- 37°C in ambient air. Positive TSBs were subcultured to a TSA, and negative TSB were incubated for a total of 48 hrs. Suspected Staph aureus colonies from TSA were identified by Gram stain, catalase, Pastorex Staph Plus, and mecA mediated oxacillin resistance by using cefoxitin (30μg) disk.

Pink colonies of any intensity on MRSASelect between 18- 28 hrs of incubation indicated the presence of MRSA. The tables below are the performance summary of the clinical studies:

Summary of read hours (incubation time)

|   | Incubation time (hours)  |   |   |   |   |   |
| --- | --- | --- | --- | --- | --- | --- |
|   |   |  18-20 | 21-23 | 24-26 | 27-28 | Total  |
|  MRSASelect Result | POS | 78 | 74 | 58 | 3 | 213  |
|   |  NEG | 245 | 233 | 225 | 27 | 730  |
|   |  Total | 323 | 307 | 283 | 30 | 943  |

MRSASelect vs. Culture + Enrichment Broth

|   | Pos | Neg | Total  |
| --- | --- | --- | --- |
|  Pos | 209 | 4 | 213  |
|  Neg | 19 | 711 | 730  |
|  Total | 228 | 715 | 943  |

Sensitivity 91.7% (87.3, 94.7)

Specificity 99.4% (98.5, 99.8)

b. Clinical specificity:

See above

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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 overall prevalence of MRSA colonization by routine culture and Tryptic Soy Broth (TSB) with 6.5% NaCl was 24.2% (228/943). The prevalence detected using routine culture alone was 22.9% (216/943) and the prevalence detected by MRSAS*elect*™ was 22.6% (213/943).

N. Proposed Labeling:
The labeling is sufficient and 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.

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**Source:** [https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO/K100589](https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO/K100589)

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