← Product Code [JSO](/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO) · K042812

# BBLCHROMAGAR MRSA (K042812)

_Becton, Dickinson & CO · JSO · Nov 22, 2004 · Microbiology · SESE_

**Canonical URL:** https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO/K042812

## Device Facts

- **Applicant:** Becton, Dickinson & CO
- **Product Code:** [JSO](/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO.md)
- **Decision Date:** Nov 22, 2004
- **Decision:** SESE
- **Submission Type:** Traditional
- **Regulation:** 21 CFR 866.1700
- **Device Class:** Class 2
- **Review Panel:** Microbiology

## Indications for Use

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

## Device Story

BBL™ CHROMagar™ MRSA is a selective/differential culture medium; utilizes chromogenic substrates and cefoxitin to detect MRSA directly from anterior nares swabs; suppresses gram-negative organisms, most S. epidermidis, and yeasts. MRSA strains grow in presence of cefoxitin; hydrolyze chromogenic substrate to produce mauve-colored colonies. Performed in clinical laboratories; manual visual inspection of plates after 24-48 hours incubation. Mauve colonies indicate potential MRSA colonization; aids infection control programs in healthcare settings. Not for diagnosing active infection or monitoring treatment.

## Clinical Evidence

Multi-site clinical evaluation (n=1794 specimens) compared BBL™ CHROMagar™ MRSA against reference methods (TSAII culture, oxacillin MIC, oxacillin screen agar, cefoxitin disk diffusion, PBP2' latex agglutination, and mecA PCR). MRSA sensitivity ranged from 93.5% to 95.7% across comparators; MSSA specificity ranged from 96.7% to 98.5%. Analytical specificity (n=416 organisms) showed 90.6% sensitivity and 98.1% specificity. Reproducibility >95%.

## Technological Characteristics

Selective/differential culture medium. Ingredients: chromopeptone (40.0 g/L), agar (14.0 g/L), chromogen mix (0.5 g/L), inhibitory agents (0.07 g/L), NaCl (25.0 g/L), cefoxitin (0.006 g/L). Principle: chromogenic substrate hydrolysis and cephalosporin-based selection. Incubation: 35-37°C for 24-48 hours. Manual method.

## 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™ Oxacillin Screen Agar (k863821)

## Submission Summary (Full Text)

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

A. 510(k) Number:
K042812

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 cefoxitin-qualitative assay

E. Applicant:
Becton, Dickinson and Company

F. Proprietary and Established Names:
BBL™ CHROMagar™ MRSA

G. Regulatory Information:
1. Regulation section:
866.1700
2. Classification:
II
3. Product code:
JSO Culture media, AST excluding Mueller Hinton agar/broth

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4. Panel:
83 Microbiology

H. Intended Use:

1. Intended use(s):
BBL™ CHROMagar™ MRSA is a selective and differential medium for the qualitative direct detection of nasal colonization by methicillin resistant Staphylococcus aureus (MRSA) to aid in the prevention and control of MRSA infections in healthcare settings. The test is performed on anterior nares swab specimens from patients and healthcare workers to screen for MRSA colonization. BBL™ CHROMagar™ MRSA is not intended to diagnose MRSA infection nor to guide or monitor treatment for infections.

2. Indication(s) for use:
BBL™ CHROMagar™ MRSA can be used to establish MRSA colonization

3. Special conditions for use statement(s):
Prescription use

4. Special instrument requirements:
Not Applicable

I. Device Description:
BBL CHROMagar™ MRSA is a chromogenic medium incorporated with cefoxitin for the direct detection of methicillin resistant Staphylococcus aureus from anterior nares specimens. Other selective agents are also incorporated in the agar to suppress gram-negative organisms, most strains of S. epidermidis and yeasts.

J. Substantial Equivalence Information:

1. Predicate device name(s):
BBL™ Oxacillin Screen Agar

2. Predicate 510(k) number(s):
k863821

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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  |
|  Differences  |   |   |
| --- | --- | --- |
|  Item | Device | Predicate  |
|  Inoculum | Direct anterior nares specimens | Isolated colonies from any source equated to a 0.5 McFarland  |
|  Incubation | 24-48 hours at 35-37 ° | 24 hours at 30-35°  |
|  Antibiotic used | cefoxitin | oxacillin  |

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

NCCLS M7-A6, Methods for Dilution Antimicrobial Susceptibility Testing; NCCLS M100-S13 Performance Standards for Antimicrobial Susceptibility Testing.

L. Test Principle:

BBL™ CHROMagar™ MRSA agar allows the direct detection and identification of MRSA with the use of specific chromogenic substrates and cefoxitin. MRSA strains will grow in the presence of cefoxitin and produce mauve-colored colonies resulting from hydrolysis of the chromogenic substrate. Additional selective agents are incorporated for the suppression of gram-negative organisms, some gram-positive organisms and yeast. Bacteria other than MRSA may utilize chromogenic substrates in the medium resulting in a blue/green colored colony or if no chromogenic substrate is utilized the colonies will appear as white or colorless.

M. Performance Characteristics (if/when applicable):

1. Analytical performance:

a. Precision/Reproducibility:

Reproducibility was established at three sites using 10 S. aureus strains including both MRSA and MSSA. Reproducibility was >95%.

b. Linearity/assay reportable range:

Not Applicable

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

Quality Control data was compiled across all three sites and all batches of CHROMagar™ MRSA agar for a total of 240 test results. All but one individual QC batch passed. The testing followed the recommendations of the QC strains listed in the package insert. This included the S. aureus ATCC® 25923 as a negative (MSSA) control and S. aureus ATCC 43300 as a positive (MRSA) control

d. Detection limit:

Not Applicable

e. Analytical specificity:

A collection of 416 organisms (203 mecA positive S. aureus, 91 mecA negative S. aureus, 86 coagulase negative staphylococci and 31 other organisms were tested using the CHROMagar™ MRSA to determine the analytical sensitivity and specificity. Results produced a sensitivity of 90.6% (184/203) and a specificity of 98.1% (206/210).

Interference Study

Eight commonly used medicinal substances, human blood and five types of specimen transport devices, were evaluated for potential interference of the chromogenic reaction on the CHROMagar MRSA medium. At a 10% concentration, a nasal spray containing phenylephrine hydrochloride demonstrated antibacterial activity on CHROMagar MRSA, as well as on the nonselective control, TSA II with 5% sheep blood.

f. Assay cut-off:

Not Applicable

2. Comparison studies:

a. Method comparison with predicate device:

The BBL™ CHROMagar™ MRSA was evaluated at four geographically diverse clinical sites. Surveillance cultures of the anterior nares were plated on Trypticase Soy Agar with 5% sheep blood (TSAII) as the reference method for recovery and then onto CHROMagar™ MRSA. Incubation of the TSAII was for 24 to 48 hours. Identification from the TSAII of S. aureus was by standard laboratory methods including a coagulase test. Susceptibility results (reference method) were determined using a microbroth dilution oxacillin MIC method (NCCLS recommended) and an oxacillin screen agar. Oxacillin

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results with a MIC of  $\leq 2\mathrm{ug / mL}$  were considered to be MSSA and results with a MIC of  $\geq 4\mathrm{ug / mL}$  were considered to be MRSA when comparing this method. Additional testing included PCR mecA detection, PBP2' Latex Agglutination and cefoxitin disk diffusion (NCCLS method). CHROMagarTM MRSA was incubated for 24 hours (+/- 4 hours) and inspected visually for mauve colored colonies and if negative reincubated for an additional 24 hour (48 h reading). Mauve colonies were considered as MRSA if appearing during the 24 visual examination and morphologically resembling staphylococci colonies but were further identified if the mauve color appeared at the 48 hour reading by using morphology and coagulase testing with confirmatory testing to include PBP2' if the TSAII was negative for S. aureus. Testing included 1794 anterior nares specimens.

Percent agreement with each method as compared to the  $\mathrm{BBL}^{\mathrm{TM}}$  CHROMagar™ is presented in the table below. Not all methods had all results available but the same set of MRSA and MSSA were tested in each system.

|  Method compared to | % agreement of MRSA | % agreement of MSSA  |
| --- | --- | --- |
|  Ox MIC | 94.9% (111/117)95% CI-89.2%,98.1% | 96.7% (201/208)95% CI 93.2%-98.6%  |
|  Ox Screen Agar | 94.9% (110/116)95% CI 89.1%,98.1% | 96.7% (202/209)95% CI-93.2%,98.6%  |
|  Cefoxitin Disc | 95% (112/118)95% CI-89.3%,98.1% | 98% (200/204)95% CI-95.1,99.5%  |
|  PBP2' Latex agglutination | 93.5% (115/123)95% CI-87.6%,97.2% | 98.5% (198/201)95% CI-95.7%,99.7%  |
|  mecA PCR | 95.7% (111/116)95% CI-90.2%,98.6% | 97% (196/202)95%CI-93.6%,98.9%  |

An additional 89 mauve colored colonies were detected on the  $\mathrm{BBL}^{\mathrm{TM}}\mathrm{CHROMagar}^{\mathrm{TM}}$  but no staphylococcus colonies were recovered by the TSA with sheep blood method. These were further identified as 15 MRSA. The remaining isolates were non S. aureus. Six of the  $\mathrm{BBL}^{\mathrm{TM}}\mathrm{CHROMagar}$  mauve colonies were positive at 24 hours and further identified as coagulase-negative staphylococcus or gram positive rods. The instructions of the test does not recommend further testing when positive at 24 hours so these would be reported falsely as MRSA detected. An additional comment is added to the results section that any suspicious mauve colonies not resembling staphylococcus at 24 hours should be further identified to increase the overall agreement.

A challenge set of 20 MRSA, MSSA strains were tested at three sites with  $100\%$  agreement with the expected result.

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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:
In the external clinical evaluation of CHROMagar MRSA, the overall prevalence of S. aureus colonization was 17.2% (340/1974), as detected by either the CHROMagar MRSA or Trypticase™ Soy Agar with 5% Sheep Blood (TSAII) plates. The overall prevalence of (non-duplicate patient) MRSA-positive specimens was 6.7% (132/1974), or about 39% (132/340) of all S. aureus. The TSAII plate MRSA-colonization detection rate was 6.5% (117/1794), while the CHROMagar MRSA rate of MRSA-colonization was 7.0% (126/1794).

N. Proposed Labeling:
The labeling is sufficient and it 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/K042812](https://fda.innolitics.com/submissions/MI/subpart-b%E2%80%94diagnostic-devices/JSO/K042812)

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