← Product Code [JSO](/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO) · K070361

# MRSASELECT (K070361)

_Bio-Rad · JSO · Sep 13, 2007 · Microbiology · SESE_

**Canonical URL:** https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO/K070361

## Device Facts

- **Applicant:** Bio-Rad
- **Product Code:** [JSO](/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO.md)
- **Decision Date:** Sep 13, 2007
- **Decision:** SESE
- **Submission Type:** Traditional
- **Regulation:** 21 CFR 866.1700
- **Device Class:** Class 2
- **Review Panel:** Microbiology

## Intended Use

MRSASelect is a selective and differential chromogenic medium for the qualitative detection of nasal colonization of methicillin resistant Staphylococcus aureus (MRSA) to aid in the prevention and control of MRSA infections in healthcare settings. The test can be performed on anterior nares specimens from patients and healthcare workers to screen for MRSA colonization. MRSASelect is not intended to diagnose MRSA infection nor to guide or monitor treatment of infection.

## Device Story

MRSASelect is a selective/differential chromogenic culture medium; used for qualitative detection of MRSA nasal colonization. Input: anterior nares specimens (direct or indirect inoculation). Principle: medium contains antibiotic/antifungal mixture and organized salts to inhibit yeast, Gram-negative, and Gram-positive bacteria (except MRSA); chromogenic substrate cleaved by S. aureus enzymatic activity produces pink colonies. Output: visual identification of pink colonies after 18-24 hours incubation at 35-37°C. Used in clinical settings; operated by laboratory personnel. Results aid infection control/prevention; not for diagnosing active infection or guiding treatment.

## Clinical Evidence

Prospective clinical evaluation at three hospitals using 3,013 anterior nares surveillance samples. Compared MRSASelect (24-hour incubation) against routine culture (Trypticase Soy Agar with 5% blood, confirmed by coagulase/oxacillin susceptibility) and BD BBL CHROMagar MRSA. Against routine culture: 96% sensitivity, 98% specificity, 87% PPV, 99% NPV. Against CHROMagar: 94% sensitivity, 99% specificity, 92% PPV, 99% NPV. No interference noted with common medicinal substances or transport devices.

## Technological Characteristics

Selective/differential chromogenic culture medium. Contains antibiotic/antifungal mixture and organized salts for selective inhibition. Manual visual inspection of colony color (pink = MRSA). Incubation: 18-24 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

- BBL CHROMagar MRSA (k042812)

## Submission Summary (Full Text)

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

A. 510(k) Number:
k070361

B. Purpose for Submission:
Premarket notification

C. Measurand:
Methicillin resistant Staphylococcus aureus (MRSA)

D. Type of Test:
Direct detection of MRSA from anterior nares specimens using specific chromogenic substrates and selective antifungal/antibiotics 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
4. Panel:
83 Microbiology

H. Intended Use:
1. Intended use(s):
MRSA Select is a selective and differential chromogenic medium for the

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qualitative detection of nasal colonization of methicillin resistant Staphylococcus aureus (MRSA) to aid in the prevention and control of MRSA infections in healthcare settings. The test can be performed on anterior nare specimens from patients and healthcare workers to screen for MRSA colonization. MRSASelect is not intended to diagnose MRSA infection nor to guide or monitor treatment of infection.

2. Indication(s) for use:

MRSASelect is indicated for the detection and direct identification of MRSA.

3. Special conditions for use statement(s):

Prescription use

4. Special instrument requirements:

Not applicable

I. Device Description:

MRSASelect is a selective and differential chromogenic medium for the qualitative detection of MRSA from anterior nares. Selective antifungal/antibiotics mixture is incorporated in the medium to inhibit the growth of yeasts, Gram negative and Gram positive bacteria except MRSA.

J. Substantial Equivalence Information:

1. Predicate device name(s): BBL CHROMagar MRSA

2. Predicate 510(k) number(s): k042812

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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 media | selective media  |
|  Differences  |   |   |
| --- | --- | --- |
|  Item | Device | Predicate  |
|  Inoculum | Direct anterior nares and Indirect (saline) | Direct nasal swabs  |
|  Incubation | 18 – 24 hours at 35 – 37°C | 24 – 48 hours at 35 - 37°C  |
|  Antibiotic used | Antibiotics | cefoxitin  |

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

CLSI M100-S17 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 organized 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 Staphylococcus aureus, leading to a strong pink coloration of the Staphylococcus aureus colonies.

Within 18-24 hours incubation time:

- Methicillin-resistant Staphylococcus aureus produce small pink colonies on MRSASelect.
- Coagulase negative methicillin-resistant staphylococci do not metabolize the chromogenic substrate and appear as colorless or white colonies (possibly light pink).
- Methicillin sensitive staphylococci (MSS) are inhibited

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M. Performance Characteristics (if/when applicable):

1. Analytical performance:

a. Precision/Reproducibility:

Reproducibility study was done at four sites. Testing was done at three sites in triplicates for three days with three lots. Duplicates were performed for three days with three lots at the fourth site. MRSA, MSSA and S. epidermidis were used. Reproducibility was >95%.

An additional 35 strains of bacteria and yeast were tested on three lots. No lot to lot variation was observed.

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 10⁴ – 10⁵ CFU/plate.

Positive Control
S. aureus ATCC 43300 at a concentration of 10³ – 10⁴ 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  |

There were a total of 56 QC results from the three sites tested 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:

Not applicable

e. Analytical specificity:

To confirm the level of detection of MRSASelect, 31 strains of MRSA were plated on the media with a dilution at 10³ CFU of a 0.5 MacFarland bacterial suspension. All strains grew on MRSASelect as small pink colonies after 24 hours incubation time.

To demonstrate the ability of MRSASelect to suppress the growth of organisms other than MRSA, 30 strains of methicillin sensitive

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Staphylococcus aureus, and 20 strains of coagulase negative methicillin sensitive Staphylococci were tested by plating a 0.5 MacFarland bacterial suspension on the medium. Pink colonies were not observed on MRSASelect after 24-hour incubation time.

## Interference Study

Two commonly used nasal sprays were evaluated for the potential interference on the performance of the MRSASelect. Three MRSA, two MSSA, two methicillin resistant coagulase negative Staph and others (K. pneumoniae and C. albicans) were tested on phenylephrine hydrochloride (1%) and oxymetazoline hydrochloride (0.05%). Bacterial growth was inhibited on the MRSASelect and the nonselective blood agar control medium. A limitation has been added to the package insert.

Four MRSA, three MSSA and one BORSA were used to test the interference effect of human blood, mucus and mucin (hog gastric) on MRSASelect. No significant interference was observed.

Four commonly used transport media were tested on the growth of MRSA on MRSASelect. There were no shifts of the bacterial count on either MRSASelect or TSA with 5% blood. The transport media did not impact the viability of MRSA.

## Cross Reactivity Study

A Cross reactivity study was performed using 91 Coagulase negative staphylococci and 30 other organisms (Gram negative rods, Strep pyogenes, N. meningitides, N. gonorrhoeae and Enterococci). Of the Coagulase negative staphylococci, there were thirteen S. epidermidis with a false negative rate of 14.3% and one S. capitis that provided weakly pinkish colonies. A limitation has been included in the package insert that S. epidermidis may develop a faint pink coloration. Of the gram negative organisms, there were seven strains that showed pinkish coloration. The reaction was reduced with the reduction of the inoculum size (from 10⁸ CFU to 10⁵ CFU). A limitation has been added to caution the user of the potential color that might be observed with selected Gram negative rods.

f. Assay cut-off:

Not applicable

2. Comparison studies:

a. Method comparison with predicate device:

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The MRSASelect™ culture media was evaluated at two clinical sites which included testing of 1772 anterior nares specimens. The recovery of MRSA on MRSASelect was compared to routine culture, which was defined as isolation of staphylococci on Trypticase Soy Agar with 5% blood, with identification confirmed by coagulase and oxacillin susceptibility. An additional 1241 samples were tested at a third site against a chromogenic medium, CHROMagar.

The optimum incubation time for MRSASelect™ culture media is 24 hours. At 24 hours, the culture media is visually inspected for small pink colonies which are considered as MRSA. Non-MRSA organisms appear as white or colorless colonies.

Percent agreement of MRSASelect™ for each method when compared to culture and another chromogenic media is presented in the table below.

Percent Agreement of MRSASelect™

|  Method | MRSA | Non-MRSA  |
| --- | --- | --- |
|  MRSASelect vs. routine culture | 95.8% (227/237) | 97.9% (1502/1535)  |
|  MRSASelect vs. a commercial chromogenic medium | 94.3% (297/315) | 99.1% (2674/2698)  |

Direct versus Indirect Inoculation

A total of 91 samples were analyzed to demonstrate that the direct and indirect inoculation procedures are equivalent. The percent agreement was 98%.

Retrospective Study

A retrospective study was evaluated at one site with 99 MRSA positive nasal swabs. At 24 hours, there were six that did not grow on the MRSASelect™. The no growth rate for MRSA at 24 hrs was 6.0% (6/99). The percent of agreement was 94% (93/99) when comparing with the routine culture, and 96% (91/95) with a commercial chromogenic medium.

b. Matrix comparison:

Not applicable

3. Clinical studies:

a. Clinical Sensitivity:

Not applicable

b. Clinical specificity:

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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 prevalence of MRSA infections has increased dramatically in hospitals and importantly the carriage rate of MRSA is rising in the community. Recent studies suggest that in the population at large this prevalence ranges between 25 – 30%.

N. Proposed Labeling:

The labeling is sufficient and it satisfies the requirement of 21CFR Part 809.10.

O. Conclusion:

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

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**Source:** [https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO/K070361](https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO/K070361)

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