(90 days)
Not Found
No
The device description and performance studies focus on a chromogenic culture medium and its ability to produce a color change based on enzymatic activity, which is a chemical/biological process, not AI/ML. There is no mention of algorithms, image processing, or data-driven decision making.
No
The device is a chromogenic medium for detecting MRSA, which aids in diagnosis and prevention, but does not treat or cure a disease.
Yes
The device is indicated for "qualitative detection of MRSA from skin structure infections" and "qualitative detection of MRSA from positive blood cultures" to "aid in the identification and diagnosis of MRSA infections," which are diagnostic purposes.
No
The device is a chromogenic agar medium, which is a physical substance used for culturing and identifying bacteria. It is not software.
Yes, this device is an IVD (In Vitro Diagnostic).
Here's why:
- Intended Use: The intended use clearly states that the device is for the "qualitative detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA)," "qualitative detection of MRSA from skin structure infections," and "qualitative detection of MRSA from positive blood cultures." These are all diagnostic purposes, aiming to identify the presence of a specific pathogen in patient samples.
- Device Description: The description details a "chromogenic medium" used to "favor the growth of MRSA" and "direct detection of MRSA strains." This describes a reagent or system used to perform a test on a biological sample.
- Clinical Studies: The document describes clinical studies where the device's performance was evaluated using patient specimens (nasal swabs, skin structure infections, positive blood cultures) and compared to a reference method. This is typical for the validation of an IVD.
- Key Metrics: The document provides performance metrics like Sensitivity and Specificity, which are standard measures used to evaluate the accuracy of diagnostic tests.
- Predicate Device: The mention of a "Predicate Device" (Remel Spectra MRSA) with a K number (K092407) indicates that this device is being compared to a previously cleared IVD, a common practice in the regulatory pathway for IVDs.
All these elements strongly indicate that the chromID™ MRSA agar is an In Vitro Diagnostic device. It is a reagent system used to perform a test on biological specimens outside of the body to aid in diagnosis or screening.
N/A
Intended Use / Indications for Use
chromID™ MRSA agar is a selective and differential chromogenic medium for :
A. The qualitative detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA), to aid in the prevention and control of MRSA in healthcare settings. The test is performed on anterior nares swab specimens from patients and healthcare workers to screen for MRSA colonization. chromID™ MRSA when used to detect nasal colonization is not intended to diagnose, guide, or monitor therapy for MRSA infections, or provide results of susceptibility to methicillin.
B. The qualitative detection of MRSA from skin structure infections. chromID™ MRSA is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA infections. Concomitant cultures for skin structure infections are necessary to recover organisms for further microbiological susceptibility testing or epidemiological typing. A negative result does not preclude MRSA infection. chromID™ MRSA is not intended to monitor treatment for MRSA infections, or provide results of susceptibility to methicillin.
C. The qualitative detection of MRSA from positive blood cultures demonstrating Gram-positive cocci on Gram stain. chromID™ MRSA is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA infections. Sub-culturing for positive blood cultures are necessary to recover organisms for further microbiological susceptibility testing or epidemiological typing. A negative result does not preclude, MRSA infection. chromID™ MRSA is not intended to monitor treatment for MRSA infections, or provide results of susceptibility to methicillin.
Product codes (comma separated list FDA assigned to the subject device)
JSO
Device Description
chromID™ MRSA agar consists of a rich nutritive base combining different peptones. It also contains a chromogenic substrate of a-glucosidase and a combination of several antibiotics, including cefoxitin, which favor the growth of MRSA including heteroresistant strains and the direct detection of MRSA strains by revealing a-glucosidase activity (patent registered), green colonies. The selective mixture of antibiotics inhibits most bacteria not belonging to the genus Staphylococcus, as well as yeasts. The MRSA strains are identified by the presence of green colonies that result from the chromogen incorporated in the medium. The chromogen targets the a-glucosidase activity of S. aureus. The a-glucosidase produced by S. aureus cleaves the chromogenic substrate, which gives a green color to the S. aureus colonies growing on the medium.
Mentions image processing
Not Found
Mentions AI, DNN, or ML
Not Found
Input Imaging Modality
Not Found
Anatomical Site
Nasal, skin, blood
Indicated Patient Age Range
Not Found
Intended User / Care Setting
Healthcare settings / laboratory tests
Description of the training set, sample size, data source, and annotation protocol
Not Found
Description of the test set, sample size, data source, and annotation protocol
Clinical studies:
chromID™ MRSA was evaluated at four clinical sites.
chromID™ MRSA performance was determined by the presence or absence of green colonies. All green colonies were tested by Gram stain, catalase and latex agglutination, and Staphylococcus aureus colonies were tested for resistance to oxacillin by the Cefoxitin Screen test. All green colonies were also tested for the presence of the mecA gene by PCR, and species identification was confirmed by VITEK® MS.
Positive results were defined for chromID™ MRSA as the growth of green colonies. All other results, including the growth of white colonies and no growth, were considered negative.
Every sample was also tested by the reference method, which included growth on Tryptic Soy agar with 5% sheep blood (BAP). Colonies suggestive of Staphylococcus species were tested by Gram stain, catalase and latex agglutination. Staphylococcus aureus isolates were further tested for resistance to Oxacillin by the Cefoxitin Screen test. All colonies resistant to Oxacillin by the Cefoxitin Screen test were tested for the presence of the mecA gene by PCR and by VITEK® MS for species confirmation.
Positive results for BAP were defined as growth of Cefoxitin resistant Staphylococcus aureus present in the media up to 48 hours. All other results, including the growth of Cefoxitin susceptible Staphylococcus aureus, growth of other species and no growth, were considered negative.
Clinical Study Sample Size:
A total of 863 positive blood culture specimens (demonstrating Gram-positive cocci) were analyzed during the clinical trial.
Summary of Performance Studies (study type, sample size, AUC, MRMC, standalone performance, key results)
Analytical Studies:
- Reproducibility: A set of ten well-characterized Staphylococcus aureus organisms (including mecA positive and mecA negative isolates) were tested in triplicate each day at 1x10^3 CFU/mL for five days at three clinical trial sites. Expected results were obtained 100% of the 450 times tested.
- Quality Control: Two quality control organisms (Staphylococcus aureus ATCC 29213 and Staphylococcus aureus ATCC 43300) were tested at each study site by chromID™ MRSA on each day of testing. Results were 100% correct for 297 times tested.
- Recovery (Limit of Detection): At 24 hours incubation time, the lowest concentration of MRSA organisms demonstrating growth with a positive result was 10 CFU/mL for one MRSA strain (ATCC® 43300) and 10^0 CFU/mL for the second MRSA strain (CDC Mu3-BR).
- Analytical Reactivity (Challenge): A challenge set composed of 80 mecA MRSA strains and 5 mecC MRSA strains was inoculated on the chromID™ MRSA agar with an inoculum equivalent to 10^3 CFU/mL. After 24 hours of incubation, 58/80 mecA MRSA strains and 4/5 mecC MRSA strains were detected.
- Cross Reactivity (Analytical Specificity): 71 non-MRSA strains representing bacterial and fungal species were inoculated onto chromID™ MRSA medium at a high inoculum level (10^6 CFU/mL). After 24 hours of incubation, forty-four strains did not grow and twenty strains grew colonies without green pigment. Green colonies (cross reactivity) were observed for three Klebsiella pneumoniae (KPC) strains, two Staphylococcus sciuri (oxacillin resistant) strains, one Enterobacter cloacae (KPC) strain, and one Staphylococcus pseudintermedius (oxacillin resistant) strain.
- Mixed Infection: 10 MRSA strains at an organism concentration of 10^3 CFU/mL were inoculated alone and in association with 3 non-targeted strains at an organism concentration of 10^6, 10^7, or 10^8 CFU/ml. MRSA was still detected on chromID MRSA in the presence of high levels of non-target organisms.
- Interfering Substances: For blood culture specimens tested in the presence of hemoglobin, triglyceride, conjugated and non-conjugated bilirubin, y-globulin, and sodium polyanethol sulfonate, all the MRSA strains were recovered. For blood culture bottles, there was no negative effect on the growth of MRSA strains on chromID MRSA.
- Incubation: The incubation times required for three MRSA strains, at an organism concentration of 10 CFU/mL, to produce positive chromID™ MRSA results was 20 hours for two strains and 27 hours for one strain.
- Expression of Resistance: Twenty eight well-characterized S. aureus (10 MRSA low level methicillin-resistant, 10 high level methicillin-resistant, 5 BORSA, and 3 MSSA strains) were evaluated with chromID™ MRSA. All low level and high level methicillin-resistant strains were detected at an inoculum ≥ 10^0 CFU/mL. At lower concentrations some strains can give colorless colonies after 24 hours of incubation.
Clinical Performance Data:
- Blood Culture Bottle-System Type Performance Summary: A total of 863 positive blood culture specimens were analyzed. MRSA was identified in 215 positive blood cultures by the reference method and 222 positive blood cultures by chromID™ MRSA (at 24 hours). Seven discordant specimens (MRSA positive result by chromID™: MRSA negative result by reference method) were observed. Two false positives were confirmed as MRSA positive. Five false positives that grew green colonies were not identified as MRSA as per latex agglutination and Cefoxitin screen results.
- BacT/ALERT® (vs. BAP) combined system: Sensitivity 100.0% (153/153), Specificity 99.0% (293/296).
- BACTEC™ (vs. BAP) combined system: Sensitivity 100.0% (62/62), Specificity 98.9% (348/352).
Key Metrics (Sensitivity, Specificity, PPV, NPV, etc.)
chromID™ MRSA (24 hours) versus BAP Reference Method (48 hours) clinical performance:
- Sensitivity: 100.0% (215/215) [95% CI: 98.3% – 100%]
- Specificity: 98.9% (641/648) [95% CI: 97.8% – 99.5%]
Predicate Device(s): If the device was cleared using the 510(k) pathway, identify the Predicate Device(s) K/DEN number used to claim substantial equivalence and list them here in a comma separated list exactly as they appear in the text. List the primary predicate first in the list.
Remel Spectra MRSA (K092407)
Reference Device(s): Identify the Reference Device(s) K/DEN number and list them here in a comma separated list exactly as they appear in the text.
Not Found
Predetermined Change Control Plan (PCCP) - All Relevant Information for the subject device only (e.g. presence / absence, what scope was granted / cleared under the PCCP, any restrictions, etc).
Not Found
§ 866.1700 Culture medium for antimicrobial susceptibility tests.
(a)
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.(b)
Classification. Class II (performance standards).
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Image /page/0/Picture/1 description: The image shows the logo for the U.S. Department of Health and Human Services. The logo consists of a stylized depiction of an eagle or bird-like figure with three curved lines representing its wings or feathers. The logo is surrounded by the text "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" arranged in a circular fashion around the emblem.
Food and Drug Administration 10903 New Hampshire Avenue Document Control Center - WO66-G609 Silver Spring, MD 20993-0002
October 25, 2016
BIOMERIEUX, INC. KAREN RUSSELL STAFF REGULATORY AFFAIRS SPECIALIST 595 ANGLUM ROAD HAZELWOOD MO 63042
Re: K162076
Trade/Device Name: chromID MRSA Regulation Number: 21 CFR 866.1700 Regulation Name: Culture medium for antimicrobial susceptibility tests Regulatory Class: II Product Code: JSO Dated: July 26, 2016 Received: July 29, 2016
Dear Ms. Russell:
We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food. Drug. and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.
If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21. Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.
Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Parts 801 and 809); medical device reporting (reporting of medical device-related adverse events) (21 CFR 803); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.
1
If you desire specific advice for your device on our labeling regulations (21 CFR Parts 801 and 809), please contact the Division of Industry and Consumer Education at its toll-free number (800) 638 2041 or (301) 796-7100 or at its Internet address
http://www.fda.gov/MedicalDevices/Resourcesfor You/Industry/default.htm. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to
http://www.fda.gov/MedicalDevices/Safety/ReportaProblem/default.htm for the CDRH's Office of Surveillance and Biometrics/Division of Postmarket Surveillance.
You may obtain other general information on your responsibilities under the Act from the Division of Industry and Consumer Education at its toll-free number (800) 638-2041 or (301) 796-7100 or at its Internet address
http://www.fda.gov/MedicalDevices/ResourcesforYou/Industry/default.htm.
Sincerely yours,
Ribhi Shawar -S
For Uwe Scherf, M.Sc., Ph.D. Director Division of Microbiology Devices Office of In Vitro Diagnostics and Radiological Health Center for Devices and Radiological Health
Enclosure
2
Indications for Use
510(k) Number (if known) K162076
Device Name chromID™ MRSA agar
Indications for Use (Describe)
chromID™ MRSA agar is a selective and differential chromogenic medium for :
A. The qualitative detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA), to aid in the prevention and control of MRSA in healthcare settings. The test is performed on anterior nares swab specimens from patients and healthcare workers to screen for MRSA colonization. chromID™ MRSA when used to detect nasal colonization is not intended to diagnose, guide, or monitor therapy for MRSA infections, or provide results of susceptibility to methicillin.
B. The qualitative detection of MRSA from skin structure infections. chromID™ MRSA is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA infections. Concomitant cultures for skin structure infections are necessary to recover organisms for further microbiological susceptibility testing or epidemiological typing. A negative result does not preclude MRSA infection. chromID™ MRSA is not intended to monitor treatment for MRSA infections, or provide results of susceptibility to methicillin.
C. The qualitative detection of MRSA from positive blood cultures demonstrating Gram-positive cocci on Gram stain. chromID™ MRSA is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA infections. Sub-culturing for positive blood cultures are necessary to recover organisms for further microbiological susceptibility testing or epidemiological typing. A negative result does not preclude, MRSA infection. chromID™ MRSA is not intended to monitor treatment for MRSA infections, or provide results of susceptibility to methicillin.
| Type of Use (Select one or both, as applicable) | |
|---|---|
| ------------------------------------------------- | -- |
X Prescription Use (Part 21 CFR 801 Subpart D)
| Over-The-Counter Use (21 CFR 801 Subpart C)
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3
chromID™ MRSA Agar: 032. 510(k) Summary
A. 510(k) Submission Information:
| Submitter's Name: | bioMérieux, Inc. |
|---|---|
| Address: | 595 Anglum Road |
| Hazelwood, MO 63042 | |
| Contact Person: | Karen Russell |
| Staff Regulatory Affairs Specialist | |
| Phone Number: | 314-731-8639 |
| Fax Number: | 314-731-8689 |
| Date of Preparation: | July 26, 2016 |
| B. Device Name: | |
| Formal/Trade Name: | chromIDTM MRSA agar |
| Classification Name: | Culture Media, Antimicrobial Susceptibility Test, Excluding |
| Mueller Hinton Agar | |
| 21 CFR 866.1700 | |
| Product Code | JSO |
| Common Name: | Culture media |
| C. Predicate Device: Remel Spectra MRSA (K092407) |
D. 510(k) Summary:
Intended Use:
chromID™ MRSA agar is a selective and differential chromogenic medium for :
A. The qualitative detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA), to aid in the prevention and control of MRSA in healthcare settings. The test is performed on anterior nares swab specimens from patients and healthcare workers to screen for MRSA colonization. chromIDTM MRSA when used to detect nasal colonization is not intended to diagnose, guide, or monitor therapy for MRSA infections, or provide results of susceptibility to methicillin.
B. The qualitative detection of MRSA from skin and skin structure infections. chromID™ MRSA is indicated for use in conjunction with other laboratory tests and clinical data
4
available to aid in the identification and diagnosis of MRSA infections. Concomitant cultures for skin and skin structure infections are necessary to recover organisms for further microbiological susceptibility testing or epidemiological typing.
A negative result does not preclude MRSA infection. chromID™ MRSA is not intended to monitor treatment for MRSA infections, or provide results of susceptibility to methicillin.
C. The qualitative detection of MRSA from positive blood cultures demonstrating Grampositive cocci on Gram stain.
chromID™ MRSA is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA infections. Subculturing for positive blood cultures are necessary to recover organisms for further microbiological susceptibility testing or epidemiological typing.
A negative result does not preclude MRSA infection. chromID™ MRSA is not intended to monitor treatment for MRSA infections, or provide results of susceptibility to methicillin.
Indications for Use:
See Intended Use Statement.
Device Description:
chromID™ MRSA agar consists of a rich nutritive base combining different peptones. It also contains a chromogenic substrate of a-glucosidase and a combination of several antibiotics, including cefoxitin, which favor the growth of MRSA including heteroresistant strains and the direct detection of MRSA strains by revealing a-glucosidase activity (patent registered), green colonies. The selective mixture of antibiotics inhibits most bacteria not belonging to the genus Staphylococcus, as well as yeasts. The MRSA strains are identified by the presence of green colonies that result from the chromogen incorporated in the medium. The chromogen targets the a-glucosidase activity of S. aureus. The a-glucosidase produced by S. aureus cleaves the chromogenic substrate, which gives a green color to the S. aureus colonies growing on the medium.
Substantial Equivalence
The similarities of chromID™ MRSA agar when compared to the predicate device are described in the following table.
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| | Device
chromID™ MRSA Agar | Predicate device
Remel Spectra™ MRSA (K092407) |
|--------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Similarities | | |
| Intended Use | chromID™ MRSA agar is a
selective and differential
chromogenic medium for :
A. The qualitative detection of
nasal colonization of methicillin-
resistant Staphylococcus aureus
(MRSA), to aid in the prevention
and control of MRSA in
healthcare settings. The test is
performed on anterior nares swab
specimens from patients and
healthcare workers to screen for
MRSA colonization. chromID™
MRSA when used to detect nasal
colonization is not intended to
diagnose, guide, or monitor
therapy for MRSA infections, or
provide results of susceptibility to
methicillin.
B. The qualitative detection of
MRSA from skin and skin
structure infections. chromID™
MRSA is indicated for use in
conjunction with other laboratory
tests and clinical data available to
aid in the identification and
diagnosis of MRSA infections.
Concomitant cultures for skin and
skin structure infections are
necessary to recover organisms
for further microbiological
susceptibility testing or
epidemiological typing. A
negative result does not preclude
MRSA infection. chromID™
MRSA is not intended to monitor
treatment for MRSA infections, or
provide results of
susceptibility to methicillin.
C. The qualitative detection of
MRSA from positive blood
cultures demonstrating Gram-
positive cocci on Gram stain. | Remel Spectra™ MRSA is a
selective and differential
chromogenic medium recommended
for use in the qualitative detection of
nasal colonization of methicillin-
resistant Staphylococcus aureus
(MRSA) to aid in the prevention and
control of MRSA in healthcare
settings. The test is performed with
anterior nares swab specimens from
patients and healthcare workers to
screen for MRSA colonization.
Spectra™ MRSA is not intended to
diagnose MRSA infection or to
guide or monitor treatment for
infections.
Spectra™ MRSA is also intended for
use in the qualitative detection of
MRSA from positive blood cultures
demonstrating Gram-positive cocci
on Gram stain. Spectra™ MRSA is
indicated for use in conjunction with
other laboratory tests and clinical
data available to the clinician as an
aid in the detection of MRSA from
patient positive blood cultures.
Spectra™ MRSA is not intended to
monitor treatment for MRSA
infections, or provide results of
susceptibility to methicillin. All
positive blood bottles should be sub-
cultured for further microbiological/
susceptibility testing. |
| | Device | Predicate device |
| | chromIDTM MRSA Agar | Remel SpectraTM MRSA (K092407) |
| | chromIDTM MRSA is indicated
for use in conjunction with other
laboratory tests and clinical data
available to aid in the
identification and diagnosis of
MRSA infections. Sub-culturing
for positive blood cultures are
necessary to recover organisms
for further microbiological
susceptibility testing or
epidemiological typing. A
negative result does not preclude
MRSA infection. chromIDTM
MRSA is not intended to monitor
treatment for MRSA infections,
or provide results of
susceptibility to methicillin. | |
| Test method | Manual | Manual |
| Specimen | Anterior nares specimens (Direct
specimens)
Positive blood cultures | Anterior nares specimens (Direct
specimens)
Positive blood cultures |
| Test Principle | chromIDTM MRSA agar consists
of a rich nutritive base combining
different peptones. It also
contains a chromogenic substrate
of α-glucosidase and a
combination of several antibiotics
including cefoxitin, which favor
the growth of MRSA including
hetero-resistant strains and the
direct detection of MRSA strains
by revealing α-glucosidase
activity (patient registered): green
colonies. | Remel SpectraTM MRSA is an
opaque medium, which uses a novel
chromogen that yields a denim-blue
color as a result of phosphatase
activity. This enzyme is present in all
Staphylococcus aureus , including
MRSA. To allow the medium to
differentiate MRSA accurately, it
contains a combination of
antibacterial compounds designed to
inhibit the growth of a wide variety
of competitor organisms. |
| | The selective mixture of
antibiotics inhibits most bacteria
not belonging to the genus
Staphylococcus , as well as yeasts.
The α-glucosidase produced by S. aureus cleaves the chromogenic
substrate, which gives a green
color to the S. aureus colonies
growing on the medium. Since
the cefoxitin has inhibited non-
methicillin-resistant S. aureus
strains, only the methicillin-
resistant S. aureus strains grow | Also included are compounds that
encourage the production of MRSA
pathogenicity marker, ensuring
expression of the phosphatase
enzyme and so providing enhanced
sensitivity and specificity. |
| | Device | Predicate device |
| | chromID™ MRSA Agar
and turn green on the media. | Remel Spectra™ MRSA (K092407) |
| Differences | | |
| Interpreting results | The α-glucosidase produced by S. aureus cleaves the chromogenic substrate, which produces a green color to the S. aureus colonies growing on the medium. Any shade of green should be interpreted as a positive result. | After 24 hours incubation, MRSA will appear as small to medium denim blue colonies against a white background. The colonies are typically smaller than on non-selective media. Other organisms (non-MRSA) will exhibit marked inhibition or produce white colonies. If after 24 hours incubation no denim blue colonies are observed, the specimen is considered negative and plates should be discarded. |
| Incubation
Conditions | 24h at 35-37°C aerobic
conditions | 24h at 35-37°C ambient air |
| Specimen | Skin and skin structure specimens | Not applicable |
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7
Both devices incorporate selective agents in the agar to inhibit most bacteria not belonging to the genus Staphylococcus, as well as yeasts. Both media are selective for methicillin-resistant Staphylococcus and contain a chromogenic substrate that turns a specific color with growth of Staphylococcus aureus colonies. The differences in the two media are the selective agents and the targeted enzyme / chromogen combination resulting in the color of the S. aureus colonies.
Performance Characteristics
Analytical Studies
The following studies were conducted as part of K151688: Recovery (Limit of Detection), Analytical Reactivity (Challenge), Cross Reactivity (Analytical Specificity), Mixed Infection, Incubation, Expression of Resistance, and Interference Substances. These studies are also summarized below.
Reproducibility – Reproducibility of the chromID™ MRSA agar was evaluated with a set of ten well-characterized Staphylococcus aureus organisms, including both mecA positive and mecA negative isolates. These organisms were tested in triplicate each day at 1x103 CFU/mL for five days at three clinical trial sites. Expected results were obtained 100% of the 450 times tested.
Quality Control - Two quality control organisms were tested at each study site by chromIDTM MRSA on each day of testing.
| Staphylococcus aureus | ATCC 29213 |
|---|---|
| Staphylococcus aureus | ATCC 43300 |
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The results for chromID™ MRSA agar QC were 100% correct for of the 297 times tested.
Recovery (Limit of Detection) - At 24 hours incubation time, the lowest concentration of MRSA organisms demonstrating growth with a positive result was 10 CFU/mL for one MRSA strain (ATCC® 43300) and 10° CFU/mL for the second MRSA strain (CDC Mu3-BR).
Analytical Reactivity (Challenge) - A challenge set composed of 80 mecA MRSA strains and 5 mecC MRSA strains was inoculated on the chromID™ MRSA agar with an inoculum equivalent to 10° CFU/mL. After 24 hours of incubation, 58/80 mecA MRSA strains and 4/5 mecC MRSA strains were detected on the chromID™ MRSA agar.
Cross Reactivity (Analytical Specificity) - To evaluate the analytical specificity of the chromID™ MRSA media, 71 non-MRSA strains representing bacterial and fungal species were inoculated onto chromID™ MRSA medium at a high inoculum level (10° CFU/mL). After 24 hours of incubation, forty-four strains did not grow and twenty strains grew colonies without green pigment. Green colonies (cross reactivity) were observed for three Klebsiella pneumoniae (KPC) strains, two Staphylococcus sciuri (oxacillin resistant) strains, one Enterobacter cloacae (KPC) strain, and one Staphylococcus pseudintermedius (oxacillin resistant) strain.
Mixed Infection - 10 MRSA strains at an organism concentration of 103 CFU/mL were inoculated alone and in association with 3 non-targeted strains at an organism concentration of 10°, 10°, or 10°CFU/ml. MRSA was still detected on chromID MRSA in the presence of high levels of non-target organisms.
Interfering Substances - For blood culture specimens tested in the presence of hemoglobin, triglyceride, conjugated and non-conjugated bilirubin, y-globulin, and sodium polyanethol sulfonate, all the MRSA strains were recovered. For blood culture bottles, there was no negative effect on the growth of MRSA strains on chromID MRSA. The bottles tested in the study included BacT/ALERT® aerobic FA. FA Plus, SA and anaerobic FN, FN Plus, SN and BacTEC™ aerobic Standard, Plus, Peds Plus and anaerobic Standard, Plus and Lytic.
Incubation - The incubation times required for three MRSA strains, at an organism concentration of 10 CFU/mL, to produce positive chromID™ MRSA results was 20 hours for two strains and 27 hours for one strain.
Expression of Resistance - Twenty eight well-characterized S. aureus (10 MRSA low level methicillin-resistant, 10 high level methicillin-resistant, 5 BORSA, and 3 MSSA strains) were evaluated with chromID™ MRSA. All low level and high level methicillinresistant strains were detected at an inoculum ≥ 10° CFU/mL. At lower concentrations some strains can give colorless colonies after 24 hours of incubation.
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Clinical studies
chromID™ MRSA was evaluated at four clinical sites. chromID™ MRSA performance was determined by the presence or absence of green colonies. All green colonies were tested by Gram stain, catalase and latex agglutination, and Staphylococcus aureus colonies were tested for resistance to oxacillin by the Cefoxitin Screen test. All green colonies were also tested for the presence of the mecA gene by PCR, and species identification was confirmed by VITEK® MS.
Positive results were defined for chromID™ MRSA as the growth of green colonies. All other results, including the growth of white colonies and no growth, were considered negative.
Every sample was also tested by the reference method, which included growth on Tryptic Soy agar with 5% sheep blood (BAP). Colonies suggestive of Staphylococcus species were tested by Gram stain, catalase and latex agglutination. Staphylococcus aureus isolates were further tested for resistance to Oxacillin by the Cefoxitin Screen test. All colonies resistant to Oxacillin by the Cefoxitin Screen test were tested for the presence of the mecA gene by PCR and by VITEK® MS for species confirmation.
Positive results for BAP were defined as growth of Cefoxitin resistant Staphylococcus aureus present in the media up to 48 hours. All other results, including the growth of Cefoxitin susceptible Staphylococcus aureus, growth of other species and no growth, were considered negative.
| Blood Culture
Information | Blood Culture
Bottle Type | Sensitivity
n/N [%]
(95% Score CI) | Specificity
n/N [%]
(95% Score CI) |
|------------------------------|------------------------------|------------------------------------------|------------------------------------------|
| BacT/ALERT®
(vs. BAP) | FA (FAN®
Aerobic) | 32/32 [100.0%]
(89.3 - 100%) | 14/14 [100.0%]
(78.5 - 100%) |
| | FA (FAN® Plus
Aerobic) | 22/22 [100.0%]
(85.1 - 100%) | 10/10 [100.0%]
(72.3 - 100%) |
| | FN (FAN®
Anaerobic) | 31/31 [100.0%]
(89.0 - 100%) | 5/5 [100.0%]
(56.6 - 100%) |
| | FN (FAN® Plus
Anaerobic) | 20/20 [100.0%]
(83.9 - 100%) | 7/7 [100.0%]
(64.6 - 100%) |
| | SA (Standard
Aerobic) | 23/23 [100.0%]
(85.7 - 100%) | 162/164 [98.8%]
(95.7 - 99.7%) |
| | SN (Standard
Anaerobic) | 25/25 [100.0%]
(86.7 - 100%) | 95/96 [99.0%]
(94.3 - 99.8%) |
| | SYSTEM
(Combined) | 153/153 [100.0%]
(97.6 - 100%) | 293/296 [99.0%]
(97.1 - 99.7%) |
| BACTEC™
(vs. BAP) | Plus Aerobic/F | 30/30 [100%]
(88.7 - 100%) | 222/225 [98.7%]
(96.2 - 99.6%) |
| | Lytic/10
Anaerobic/F | 32/32 [100%]
(89.3 - 100%) | 126/127 [99.2%]
(95.7 - 99.9%) |
| | SYSTEM
(Combined) | 62/62 [100.0%]
(94.2 - 100%) | 348/352 [98.9%]
(97.1 - 99.6%) |
Blood Culture Bottle-System Type Performance Summary
A total of 863 positive blood culture specimens (demonstrating Gram-positive cocci) were analyzed during the clinical trial. One hundred eighty-seven cultures were removed
10
due to low prevalence of target (in specific blood culture bottle type) and protocol deviations.
In the clinical study, MRSA was identified in 215 positive blood cultures by the reference method and 222 positive blood cultures by chromID™ MRSA (at 24 hours). Seven discordant specimens (MRSA positive result by chromID™: MRSA negative result by reference method) were observed. Two false positives were confirmed as MRSA positive. Five false positives that grew green colonies were not identified as MRSA as per latex agglutination and Cefoxitin screen results.
| chromID™ MRSA (24 hours) versus BAP Reference Method (48 | ||
|---|---|---|
| Performance | 2-sided 95% CI | |
| Sensitivity | 100.0% (215/215) | [98.3% – 100]% |
| Specificity | 98.9% (641/648) | [97.8% – 99.5]% |
chromID™ MRSA Clinical Performance Data hours) ch
The prevalence of MRSA detected by BAP plus confirmatory testing for MRSA was 24.9% (215/863), and the prevalence detected by chromID™ MRSA at 24 hours was 25.7% (222/863).