KEYPATH(TM) MRSA/MSSA BLOOD CULTURE TEST- BT

K102342 · Microphage, Inc. · OUS · May 5, 2011 · Microbiology

Device Facts

• Record ID: K102342
• Device Name: KEYPATH(TM) MRSA/MSSA BLOOD CULTURE TEST- BT
• Applicant: Microphage, Inc.
• Product Code: OUS · Microbiology
• Decision Date: May 5, 2011
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 866.2050
• Device Class: Class 1

Intended Use

The KeyPath™ MRSA/MSSA Blood Culture Test – BT is a qualitative in vitro diagnostic test for the timely identification of Staphylococcus aureus (S. aureus) and determination of methicillin susceptibility (MSSA) or methicillin resistance (MRSA) directly from positive blood cultures. The Test uses bacteriophage amplification to identify the presence of S. aureus and assess the phenotypic response of the target organism to cefoxitin, an indicator of oxacillin (a methicillin analog) resistance. The assay is performed directly on positive blood culture specimens that are determined as Gram Positive Cocci in singles (GPC) or as Gram Positive Cocci in Clusters (GPCC) by Gram stain. The KeyPath™ MRSA/MSSA Blood Culture Test – BT is performed directly on positive blood culture specimens from BD BACTEC™ blood culture bottles (Plus Aerobic/F and Plus Anaerobic/F). The Test is indicated for use in conjunction with other laboratory and clinical data available to the physician as an aid in the detection of MRSA/MSSA from positive blood cultures. Subculturing of positive blood cultures is necessary for additional susceptibility test determinations, differentiation of mixed growth and for epidemiological typing.

Device Story

Device uses lytic bacteriophage specific to S. aureus for amplification-based detection; differentiates MRSA/MSSA via phenotypic response to cefoxitin. Input: positive blood culture (Bactec bottles). Process: bacteriophage infects S. aureus, replicates, and lyses host; cefoxitin inhibits amplification in MSSA but not MRSA. Output: dual-lane lateral flow immunoassay (LFI) with colloidal gold; visual signal indicates presence/resistance. Used in clinical labs by professional staff. Results aid physicians in rapid identification of MRSA/MSSA, potentially accelerating appropriate antibiotic therapy.

Clinical Evidence

Prospective clinical trial at four sites with 1116 paired samples. Sensitivity 91.8%, specificity 98.3% for S. aureus detection. Category agreement with cefoxitin disk diffusion: 98.9% for MRSA, 99.4% for MSSA. Reproducibility 99.4%. No significant interference from antibiotics, antivirals, or blood components.

Technological Characteristics

Phenotypic test using lytic bacteriophage amplification and lateral flow immunoassay with colloidal gold particles. Detects S. aureus and methicillin resistance via cefoxitin inhibition. Standalone manual test format. No electronic components or software algorithms.

Indications for Use

Indicated for patients 18 years or older with positive blood cultures (Bactec system) identified as Gram Positive Cocci in singles or clusters by Gram stain. Used as an aid in detecting MRSA/MSSA. Not intended to monitor treatment.

Regulatory Classification

Identification

A staphylococcal typing bacteriophage is a device consisting of a bacterial virus intended for medical purposes to identify pathogenic staphylococcal bacteria through use of the bacteria's susceptibility to destruction by the virus. Test results are used principally for the collection of epidemiological information.

Predicate Devices

• BD GeneOhm™ StaphSR Assay (K071026)
• Wellcome (Remel) Staphaurex® ZL30 (K851949)
• Oxoid PBP2' Latex Agglutination (K011710)
• BBL (BD) cefoxitin 30 µg Sensi-Disc (preAmendment)
• BBL (BD) oxacillin 1 µg Sensi-Disc (preAmendment)
• Coagulase Test (preAmendment)
• Catalase Test (preAmendment)

Submission Summary (Full Text)

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Image /page/0/Picture/0 description: The image shows the handwritten text "K102342" above a logo. The logo is a semi-circular shape with a dark gray section on the left and a lighter gray section on the right. The text appears to be written in black ink on a white background.

# MIC ROP H A G E

## 510(k) Summary

As required by 21 CFR Section 807.92(c).

| Submitted by: | MicroPhage, Inc.<br>2400 Trade Centre Ave<br>Longmont, CO 80503 | MAY - 5 2011 |
|------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------|
| Phone number: | [phone] | |
| Fax number: | [phone] | |
| Contact: | Drew Smith, PhD | |
| Date of Preparation: | April 29, 2011 | |
| Device:<br>Trade name: | KeyPathTM MRSA/MSSA Blood Culture Test - BT | |
| Common name: | Bacterial Identification and Antimicrobial Susceptibility Test (ID/AST);<br>KeyPathTM AST; Methicillin-resistant Staphylococcus aureus (MRSA)<br>and Methicillin-sensitive Staphylococcus aureus (MSSA) from positive<br>blood culture bottles test. | |
| Type of Test: | Bacteriophage amplification, Methicillin-resistant<br>Staphylococcus aureus (MRSA) and Methicillin-sensitive Staphylococcus<br>aureus (MSSA), qualitative | |
| Regulation section: | 866.2050 - Staphylococcal typing bacteriophage | |
| Classification: | I | |
| Product code: | OUS | |
| Panel: | 83 Microbiology | |

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## MicroPhage KeyPath™ MRSA/MSSA Blood Culture Test - BT: 510(k) Summary

| Predicate Devices: | | BD GeneOhm™ StaphSR Assay |
|--------------------|----------------|-----------------------------------------|
| | K851949 | Wellcome (Remel) Staphaurex® ZL30 |
| | K011710 | Oxoid PBP2' Latex Agglutination |
| | (preAmendment) | BBL (BD) cefoxitin 30 µg Sensi-Disc |
| | (preAmendment) | BBL (BD) oxacillin 1 µg Sensi-Disc |
| | (preAmendment) | Coagulase Test (multiple manufacturers) |
| | (preAmendment) | Catalase Test (multiple manufacturers) |

### Device Description:

The KeyPath™ MRSA/MSSA Blood Culture Test – BT uses lytic bacteriophage, specific for Staphylococcus aureus, as an amplification technology for detection of S. aureus and determination of methicillin resistance or susceptibility in positive blood cultures. To detect S. aureus (ID Reaction Tube), the bacteriophage infect the S. aureus (if present), replicate within the host (culminating in bacterial lysis) and over the incubation period, produce several cvcles of bacteriophage amplification. In a separate Reaction Tube (RS), the Test uses cefoxitin (an oxacillin and methicillin analog) which inhibits bacteriophage amplification for susceptible organisms (MSSA) and fails to inhibit bacteriophage amplification when the organism is resistant to methicillin (MRSA). The Test then uses a self-performing immunoassay (Detector) to detect the increase in concentration of bacteriophage using antibodies specific to the Test bacteriophage, and calibrated such that at above a threshold concentration, it produces a visible signal.

### Device Intended Use:

The KeyPath™ MRSA/MSSA Blood Culture Test – BT is a qualitative in vitro diagnostic test for the timely identification of Staphylococcus aureus (S. aureus) and determination of methicillin susceptibility (MSSA) or methicillin resistance (MRSA) directly from positive blood cultures.

The Test uses bacteriophage amplification to identify the presence of S. aureus and assess the phenotypic response of the target organism to cefoxitin, an indicator of oxacillin (a methicillin analog) resistance.

The assay is performed directly on positive blood culture specimens that are determined as Gram Positive Cocci in singles (GPC) or as Gram Positive Cocci in Clusters (GPCC) by Gram stain.

The KeyPath™ MRSA/MSSA Blood Culture Test – BT is performed directly on positive blood culture specimens from BD BACTEC™ blood culture bottles (Plus Aerobic/F and Plus Anaerobic/F).

The Test is indicated for use in conjunction with other laboratory and clinical data available to the physician as an aid in the detection of MRSA/MSSA from positive blood cultures.

Subculturing of positive blood cultures is necessary for additional susceptibility test determinations, differentiation of mixed growth and for epidemiological typing.

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## Substantial Equivalence:

The KeyPath™ MRSA/MSSA Blood Culture Test - BT is substantially equivalent to the BD GeneOhm™ StaphSR Assay (510(k)# K071026). Both assays are indicated for the identification/detection of S. aureus from blood culture positives and both are indicated for determination/detection of MRSA. Though each use different technologies (bacteriophage amplification vs. RT - PCR), and the MicroPhage Test is phenotypic as opposed to genotypic, both perform with high sensitivity and specificity to their intended targets. Table 1 summarizes the major similarities and differences between these two methods.

Table 1 - Similarities and Differences between the KeyPath™ MRSA/MSSA Blood Culture Test - BT and the BD GeneOhm™ StaphSR assay.

| SIMILARITIES | | |
|------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Item | KeyPath™ MRSA/MSSA Blood Culture Test - BT | BD GeneOhm™ StaphSR Assay |
| Intended Use | The KeyPath™ MRSA/MSSA Blood Culture Test - BT<br>is a qualitative in vitro diagnostic test for the timely<br>identification of <i>Staphylococcus aureus</i> ( <i>S. aureus</i> ) and<br>determination of methicillin susceptibility (MSSA) or<br>methicillin resistance (MRSA) directly from positive<br>blood cultures. | The BD GeneOhm™ StaphSR<br>Assay is a qualitative in vitro<br>diagnostic test for the <b>rapid<br/>detection</b> of <i>Staphylococcus<br/>aureus</i> ( <i>SA</i> ) and methicillin-<br>resistant <i>Staphylococcus aureus</i><br>(MRSA) directly from positive<br>blood culture. |
| | The Test uses bacteriophage amplification to identify the<br>presence of <i>S. aureus</i> and assess the phenotypic response<br>of the target organism to cefoxitin, an indicator of<br>oxacillin (a methicillin analog) resistance. | The assay utilizes polymerase chain<br>reaction (PCR) for the amplification<br>of specific targets and fluorogenic<br>target-specific hybridization probes<br>for the real-time detection of the<br>amplified DNA. |
| | The assay is performed directly on positive blood<br>culture specimens that are determined as Gram<br>Positive Cocci in singles (GPC) or as Gram Positive<br>Cocci in Clusters (GPCC) by Gram stain. | The assay is performed on gram<br>positive cocci, identified by Gram<br>stain, from positive blood<br>cultures. The BD GeneOhm™<br>StaphSR Assay is not intended to<br>monitor treatment for MRSA/SA<br>infections. Subculturing of positive<br>blood cultures is necessary for |
| | The KeyPath™ MRSA/MSSA Blood Culture Test - BT<br>is performed directly on positive blood culture specimens<br>from BD BACTECTM blood culture bottles (Plus<br>Aerobic/F and Plus Anaerobic/F). | |
| | The Test is indicated for use in conjunction with other<br>laboratory and clinical data available to the physician as<br>an aid in the detection of MRSA/MSSA from positive<br>blood cultures. | StaphSR Assay is not intended to<br>monitor treatment for MRSA/SA<br>infections. Subculturing of positive<br>blood cultures is necessary for |
| | Subculturing of positive blood cultures is necessary for<br>additional susceptibility test determinations,<br>differentiation of mixed growth and for epidemiological<br>typing | further susceptibility testing. |
| Single Use | Yes | Yes |
| Indication for<br>Use | Professional Use | Professional Use |
| Interpretation<br>of results | Visual | Visual |
| Patient<br>population | Clinical patients | Clinical patients |
| Specimen type | Positive blood culture | Positive blood culture |

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| Assay controls | Pos Control 1: MRSA | Pos Control: MRSA |
|----------------|---------------------|-------------------|
| | Pos Control 2: MSSA | Pos Control: SA |
| | Neg Control: NSA | Neg Control: NSA |

| | DISSIMILARITIES | |
|----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Item | KeyPathTM MRSA/MSSA Blood Culture Test - BT | BD GeneOhmTM StaphSR Assay |
| Time to result | 5 hours | 60-75 minutes |
| Mode of action | The test uses bacteriophage amplification with cefoxitin to quickly determine the presence of MRSA and MSSA in positive blood cultures. | The assay utilizes polymerase chain reaction (PCR) for the amplification of specific targets and fluorogenic target-specific hybridization probes for the real-time detection of the amplified DNA. |
| Assay format | Amplification: bacteriophage amplification<br>Detection: Lateral flow immunoassay with colloidal gold particles with monoclonal antibodies specific to assay bacteriophage. | Amplification: polymerase chain reaction (PCR)<br>Detection: Fluorogenic target-specific hybridization probes of the amplified DNA. |

*Bolded and underlined portions indicates similarities of intended use.

The KeyPath™ MRSA/MSSA Blood Culture Test – BT is substantially equivalent to combined Coagulase and Catalase Test (both pre-amendment). Both Coag/Cat and MicroPhage Tests are indicated for the identification or detection of S. aureus and are phenotypic tests. Table 2 summarizes the major similarities and differences between these two methods.

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Table 2 – Similarities and Differences between the KeyPath™ MRSA/MSSA Blood Culture Test – BT and the Coagulase Tube and Catalase Slide Tests.

| SIMILARITIES | | |
|---------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Item | KeyPath™ MRSA/MSSA Blood Culture Test - BT | Coagulase Tube, Catalase Slide Tests (pre-amendment) |
| Intended Use | The KeyPath™ MRSA/MSSA Blood Culture Test - BT is a qualitative in vitro diagnostic test for the timely identification of Staphylococcus aureus (S. aureus) and determination of methicillin susceptibility (MSSA) or methicillin resistance (MRSA) directly from positive blood cultures. The Test uses bacteriophage amplification to identify the presence of S. aureus and assess the phenotypic response of the target organism to cefoxitin, an indicator of oxacillin (a methicillin analog) resistance. The assay is performed directly on positive blood culture specimens that are determined as Gram Positive Cocci in singles (GPC) or as Gram Positive Cocci in Clusters (GPCC) by Gram stain. The KeyPath™ MRSA/MSSA Blood Culture Test - BT is performed directly on positive blood culture specimens from BD BACTECTM blood culture bottles (Plus Aerobic/F and Plus Anaerobic/F). The Test is indicated for use in conjunction with other laboratory and clinical data available to the physician as an aid in the detection of MRSA/MSSA from positive blood cultures. Subculturing of positive blood cultures is necessary for additional susceptibility test determinations, differentiation of mixed growth and for epidemiological typing | The Coagulase Tube and Catalase Slide Tests (multiple manufacturers) are qualitative in vitro diagnostic test for the identification of Staphylococcus aureus (SA) directly from isolated colonies from a positive blood culture. "Positive" results for both catalase and coagulase are indicative of S. aureus. The assays contain rabbit serum with EDTA for Coagulase Test and peroxide (H2O2) for Catalase Test substrates which will react with coagulase and catalase enzymes expressed by S. aureus. A clumping of rabbit serum confirms the presence of coagulase and production of O₂ bubbles confirms the presence of catalase (i.e. both results indicating presence of S. aureus). The assay is performed on gram positive cocci which have been isolated by streaking on culture plates, identified by Gram stain, from positive blood cultures. Further subculturing of positive blood cultures are necessary for susceptibility testing. |
| Single Use | Yes | Yes |
| Indication for Use | Professional Use | Professional Use |
| Interpretation of results | Visual | Visual |
| Patient population | Clinical patients | Clinical patients |

Table 2 – Similarities and Differences between the KeyPath™ MRSA/MSSA Blood Culture Test – BT and Coagulase/Catalase Tests for S. aureus determination.

| DISSIMILARITIES | | |
|-----------------|------------------------------------------------|------------------------------------------------------------------------------------------------|
| Item | KeyPathTM MRSA/MSSA Blood Culture<br>Test - BT | Coagulase Tube, Catalase<br>Slide Tests<br>(pre-amendment) |
| Specimen type | Positive blood culture | Overnight purified plate culture (i.e. isolated<br>colonies) originating from a Positive blood |

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| DISSIMILARITIES | | |
|-----------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Item | KeyPath™ MRSA/MSSA Blood Culture<br>Test - BT | Coagulase Tube, Catalase<br>Slide Tests<br>(pre-amendment) |
| Time to result | 5 hours | culture<br>Catalase: 5 minutes<br>Coagulase: 4-24 hours |
| Mode of action | The test uses bacteriophage amplification with<br>cefoxitin to quickly determine the presence of<br>MRSA and MSSA in positive blood cultures. | The assays contain rabbit serum with EDTA<br>for the Coagulase Test and peroxide ( $H_2O_2$ )<br>for the Catalase Test, substrates which will<br>react with coagulase and catalase enzymes<br>expressed by <i>S. aureus</i> . A clumping of rabbit<br>serum confirms the presence of coagulase and<br>production of $O_2$ bubbles confirms the<br>presence of catalase. Both results indicate the<br>presence of <i>S. aureus</i> . |
| Assay format | Amplification: bacteriophage amplification<br><br>Detection: Lateral flow immunoassay with<br>colloidal gold particles with monoclonal<br>antibodies specific to assay bacteriophage. | Amplification: none<br><br>Detection: Clumping of coagulase substrate<br>and $O_2$ gas production (i.e. bubbles) of<br>catalase substrate when metabolized by the<br>respective enzymes. |

*Bolded and underlined portions indicates similarities of intended use.

The KeyPath™ MRSA/MSSA Blood Culture Test – BT is substantially equivalent to Remel Staphaurex® (510(k)# K851949). Both assays are indicated for the identification or detection of S. aureus and are phenotypic tests. Additionally, both use antibody-based detection methods (lateral flow immunoassay vs. latex agglutination). Table 3 summarizes the major similarities and differences between these two methods.

Table 3 - Similarities and Differences between the KeyPath™ MRSA/MSSA Blood Culture Test - BT and Wellcome (Remel) Staphaurex for S. aureus determination.

| SIMILARITIES | | |
|--------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Item | KeyPathTM MRSA/MSSA Blood Culture Test – BT | Remel Staphaurex® |
| Intended Use | The KeyPathTM MRSA/MSSA Blood Culture Test - BT is a<br>qualitative <i>in vitro</i> diagnostic test for the timely<br>identification of <i>Staphylococcus aureus</i> ( <i>S. aureus</i> ) and<br>determination of methicillin susceptibility (MSSA) or<br>methicillin resistance (MRSA) directly from positive blood<br>cultures.<br><br>The Test uses bacteriophage amplification to identify the<br>presence of <i>S. aureus</i> and assess the phenotypic response of<br>the target organism to cefoxitin, an indicator of oxacillin (a<br>methicillin analog) resistance.<br><br>The assay is performed directly on positive blood culture<br>specimens that are determined as Gram Positive Cocci in<br>singles (GPC) or as Gram Positive Cocci in Clusters<br>(GPCC) by Gram stain.<br><br>The KeyPathTM MRSA/MSSA Blood Culture Test - BT is<br>performed directly on positive blood culture specimens<br>from BD BACTECTM blood culture bottles (Plus Aerobic/F | Staphaurex® is a rapid slide<br>agglutination procedure for<br>differentiating staphylococci<br>which possess clumping factor<br>and/or protein A, particularly<br><i>Staphylococcus aureus</i> , from<br>staphylococci which possess<br>neither of these factors. |

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| SIMILARITIES | | |
|------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------|
| Item | KeyPathTM MRSA/MSSA Blood Culture Test – BT<br>and Plus Anaerobic/F).<br><br>The Test is indicated for use in conjunction with other<br>laboratory and clinical data available to the physician as an<br>aid in the detection of MRSA/MSSA from positive blood<br>cultures.<br><br>Subculturing of positive blood cultures is necessary for<br>additional susceptibility test determinations, differentiation<br>of mixed growth and for epidemiological typing | Remel Staphaurex® |
| Single Use | Yes | Yes |
| Indication for<br>Use | Professional Use | Professional Use |
| Interpretation<br>of results | Visual | Visual |
| Patient<br>populations | Clinical patients | Clinical patients |
| Assay<br>controls | Pos Control 1: MRSA<br>Pos Control 2: MSSA<br>Neg Control: NSA | Pos Control: SA<br>Neg Control: NSA |

| DISSIMILARITIES | | |
|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------|
| Item | KeyPathTM MRSA/MSSA Blood Culture Test -<br>BT | Remel Staphaurex® |
| Specimen type | Positive blood culture | Overnight Purified Culture<br>(16-24hr) |
| Time to result | 5 hours | 10 - 15 minutes |
| Mode of action | The test uses bacteriophage amplification with<br>cefoxitin to quickly determine the presence of<br>MRSA and MSSA in positive blood cultures. | The test detects the presence of clumping<br>factor and protein A using coated latex<br>particles which agglutinate in a rapid<br>slide procedure. |
| Assay format | Amplification: bacteriophage amplification<br>Detection: Lateral flow immunoassay with<br>colloidal gold particles with monoclonal<br>antibodies specific to assay bacteriophage. | Amplification: none<br>Detection: Agglutination of latex<br>particles. |

* Bolded and underlined portions indicates similarities of intended use.

The KeyPath™ MRSA/MSSA Blood Culture Test – BT is substantially equivalent to the Oxoid PBP2' Latex Agglutination test (510(k)# K011710). Both assays are indicated for the determination or identification of MRSA by surrogate markers (bacteriophage amplification vs. penicillin binding protein 2'). Additionally, both use antibody-based detection methods (lateral flow immunoassay vs. latex agglutination) and are phenotypic tests. Table 4 summarizes the major similarities and differences between these two methods.

Table 4 - Similarities and Differences between the KeyPath™ MRSA/MSSA Blood Culture Test - BT and Oxoid PBP2' Latex Agglutination for MRSA determination.

| | SIMILARITIES | |
|--------------|----------------------------------------------------|-----------------------------------------|
| Item | KeyPathTM MRSA/MSSA Blood Culture Test – BT | Oxoid PBP2' Latex<br>Agglutination Test |
| Intended Use | The KeyPathTM MRSA/MSSA Blood Culture Test – BT is | This test is a rapid latex |

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| | SIMILARITIES | |
|------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------|
| Item | KeyPathTM MRSA/MSSA Blood Culture Test – BT | Oxoid PBP2' Latex Agglutination Test |
| | a qualitative <i>in vitro</i> diagnostic test for the timely<br>identification of <i>Staphylococcus aureus</i> ( <i>S. aureus</i> ) and<br>determination of methicillin susceptibility (MSSA) or<br>methicillin resistance (MRSA) directly from positive<br>blood cultures.<br>The Test uses bacteriophage amplification to identify the<br>presence of <i>S. aureus</i> and assess the phenotypic response<br>of the target organism to cefoxitin, an indicator of oxacillin<br>(a methicillin analog) resistance.<br>The assay is performed directly on positive blood culture<br>specimens that are determined as Gram Positive Cocci in<br>singles (GPC) or as Gram Positive Cocci in Clusters<br>(GPCC) by Gram stain.<br>The KeyPathTM MRSA/MSSA Blood Culture Test – BT is<br>performed directly on positive blood culture specimens<br>from BD BACTECTM blood culture bottles (Plus<br>Aerobic/F and Plus Anaerobic/F).<br>The Test is indicated for use in conjunction with other<br>laboratory and clinical data available to the physician as an<br>aid in the detection of MRSA/MSSA from positive blood<br>cultures.<br>Subculturing of positive blood cultures is necessary for<br>additional susceptibility test determinations, differentiation agglutination assay, detecting<br>PBP2' (also called PBP2a), in<br>isolates of <i>Staphylococcus</i> , as an<br>aid in identifying methicillin-<br>resistant <i>Staphylococcus aureus</i><br>(MRSA) and methicillin-resistant<br>coagulase-negative staphylococci. | |
| Single Use | Yes | Yes |
| Indication for<br>Use | Professional Use | Professional Use |
| Interpretation<br>of results | Visual | Visual |
| Patient<br>populations | Clinical patients | Clinical patients |
| Assay controls | Pos Control 1: MRSA<br>Pos Control 2: MSSA<br>Neg Control: NSA | Pos Control: MRSA<br>Neg Control: NSA |

| DISSIMILARITIES | | |
|-----------------|---------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Item | KeyPath™ MRSA/MSSA Blood Culture Test -<br>BT | Oxoid PBP2' Latex Agglutination<br>Test |
| Specimen | Positive blood culture | Overnight Purified Culture (16 - 24<br>hrs) |
| Time to result | 5 hours | 45 minutes |
| Mode of action | The test uses bacteriophage amplification with<br>cefoxitin to determine the presence of MRSA and<br>MSSA in positive blood cultures. | Latex particles sensitized with a<br>monoclonal antibody against PBP2'<br>specifically react with methicillin-<br>resistant staphylococci to cause<br>agglutination visible to the unaided<br>eye. |
| Assay format | Amplification: bacteriophage amplification<br>Detection: lateral flow immunoassay with | Amplification: none |

.

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| DISSIMILARITIES | | | |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------|--|
| ltem | KevPath "31 MRSA/MSSA Blood Culture Test - | Oxoid PBP2' Latex Agglutination | |
| | BT | Test | |
| | colloidal gold particles with monoclonal | Detection: | |
| | antibodies specific to assay bacteriophage. | Agglutination of latex particles | |
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* Bolded and underlined portions indicates similarities of intended use.

The KeyPath™ MRSA/MSSA Blood Culture Test - BT is substantially equivalent to the BD BBL 30 µg cefoxitin Sensi-Disc and BD BBL 1 µg oxacillin Sensi-Disc (both pre-Amendment devices). All three assays are indicated for the phenotypic determination of MRSA. Additionally, all use a viable culture of bacteria (e.g., S. aureus) to guide interpretation of results. though the MicroPhage Test does not require a subculture of the isolate. All methods produce highly sensitive and specific results for their indicated determinations with low rates of major and very major discrepancies. Table 5 summarizes the major similarities and differences between these two methods.

Table 5 - Similarities and Differences between the KeyPath™ MRSA/MSSA Blood Culture Test - BT, the BD BBL 30 ug cefoxitin Sensi-Disc, and the BD BBL 1 ug oxacillin Sensi-Disc for MRSA/MSSA breakpoint determinations.

| SIMILARITIES | | | |
|--------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------…