Test Id : MECPI
Methicillin Resistance Gene, Molecular Detection, PCR, Varies
Useful For
Suggests clinical disorders or settings where the test may be helpful
Detecting mecA in staphylococcal bacterial isolates
Evaluating treatment options when oxacillin or cefoxitin breakpoints are unavailable (eg, certain Staphylococcus species other than Staphylococcus aureus)
Predicting antimicrobial resistance when bacterial growth is inadequate for phenotypic antimicrobial susceptibility testing (eg, staphylococcal small colony variants)
Assessing discrepancies amongst cefoxitin and oxacillin phenotypic testing results or penicillin-binding protein 2a test results
Highlights
This rapid molecular test detects mecA DNA associated with prediction of resistance to methicillin and other applicable beta-lactam antibiotics in isolates of Staphylococcus species.
Method Name
A short description of the method used to perform the test
Real-Time Polymerase Chain Reaction (PCR)/Reverse Transcription PCR (RT-PCR)
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
mecA
Staph
Staphylococcus
Specimen Type
Describes the specimen type validated for testing
Varies
Shipping Instructions
1. For shipping information, see Infectious Specimen Shipping Guidelines.
2. Place specimen in a large infectious container and label as an etiologic agent/infectious substance.
Necessary Information
Organism identification and specimen source are required.
ORDER QUESTIONS AND ANSWERS
| Question ID | Description | Answers |
|---|---|---|
| MESCR | Specimen Source |
31208-2 |
| MEORG | Organism Identified by Client |
43409-2 |
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Supplies: Infectious Container, Large (T146)
Container/Tube: Agar slant or other appropriate media
Specimen Volume: Organism in pure culture
Collection Instructions:
1. Perform isolation of bacteria.
2. Organism must be in pure culture, actively growing. Do not submit mixed cultures.
Special Instructions
Library of PDFs including pertinent information and forms related to the test
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
See Specimen Required
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Agar plate Mixed culture | Reject |
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Varies | Ambient (preferred) | ||
| Refrigerated | |||
Useful For
Suggests clinical disorders or settings where the test may be helpful
Detecting mecA in staphylococcal bacterial isolates
Evaluating treatment options when oxacillin or cefoxitin breakpoints are unavailable (eg, certain Staphylococcus species other than Staphylococcus aureus)
Predicting antimicrobial resistance when bacterial growth is inadequate for phenotypic antimicrobial susceptibility testing (eg, staphylococcal small colony variants)
Assessing discrepancies amongst cefoxitin and oxacillin phenotypic testing results or penicillin-binding protein 2a test results
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The presence of mecA has been associated with methicillin resistance in staphylococcal isolates. Rapid identification of mecA in staphylococcal isolates will help in determining which antimicrobial therapy to use when treating infections due to methicillin-resistant Staphylococcus aureus or methicillin-resistant Staphylococcus species other than S aureus.
Bacteria can acquire resistance to certain beta-lactam antibiotics through a variety of mechanisms. One such mechanism is the mecA gene. The mecA gene encodes penicillin-binding protein 2a (PBP2a), which has a low affinity for beta-lactam antibiotics. Bacteria expressing this gene can maintain cell wall synthesis even in the presence of beta-lactam antibiotics.
Testing of bacterial isolates by molecular methods may be needed when oxacillin or cefoxitin breakpoints are unavailable (eg, certain Staphylococcus species other than S aureus) or when discrepancies exist among cefoxitin and oxacillin phenotypic antimicrobial susceptibility testing results or PBP2a results. Use of this assay may also be helpful when isolates do not grow adequately for phenotypic antimicrobial susceptibility testing (eg, staphylococcal small colony variants).
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Not detected
Interpretation
Provides information to assist in interpretation of the test results
A positive result indicates the presence of the methicillin resistance gene (mecA) in the bacterial isolate.
A negative result indicates the absence of detectable DNA in the bacterial isolate.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Only pure isolates of staphylococcal species should be tested.
This test should be used in conjunction with phenotypic antimicrobial susceptibility tests, when available, and interpreted considering the patient's clinical condition.
This US Food and Drug Administration-modified assay will not predict methicillin resistance caused by mechanisms other than mecA. Methicillin resistance due to mecC is not assessed by this assay.
False-negative results may occur due to the presence of mecA in quantities lower than the limit of detection of the assay.
Mutations or polymorphisms in primer or probe binding regions may affect detection of new or unknown Staphylococcus aureus or methicillin-resistant S aureus variants resulting in a false-negative result.
Xpert SA Nasal Complete assay results may sometimes be invalid due to a failed sample processing control, an error, or lack of a result and may require retesting, which can lead to a delay in obtaining final results.
Supportive Data
Staphylococcal bacterial isolates were tested for the presence of mecA by the Cepheid GeneXpert - Xpert SA Nasal Complete compared to Mayo Clinic’s laboratory developed test (LDT) MARP / mecA, Molecular Detection, PCR, Varies. There was 95% or greater concordance for the detection of 25 mecA negative methicillin susceptible Staphylococcus species other than Staphylococcus aureus, 10 mecA negative methicillin susceptible S aureus, and 20 mecA positive methicillin-resistant S aureus. Greater than 95% concordance was achieved for 25 mecA positive methicillin-resistant Staphylococcus species other than S aureus isolates. Additionally, 10 isolates of Staphylococcus saccharolyticus and 10 isolates of small colony variant staphylococci were tested for the presence of mecA by both the Cepheid GeneXpert - Xpert SA Nasal Complete platform and the LDT, yielding 95% or greater correlation.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Xpert SA Nasal Complete 300-8799. Package insert: Cepheid; Rev H, 09/2019
2. Ali GH, Seiffein N. Association of some virulence genes in methicillin resistant and methicillin sensitive Staphylococcus aureus infections isolated in community with special emphasis on pvl/mecA genes profiles in Alexandria, Egypt. Gene Reports. 2021;25:101334. doi:10.1016/j.genrep.2021.101334
3. Seker E, Ozenc E, Turedi OK, Yilmaz M. Prevalence of mecA and pvl genes in coagulase negative staphylococci isolated from bovine mastitis in smallholder dairy farms in Turkey. Anim Biotechnol. 2022;34(7):2427-2432. doi:10.1080/10495398.2022.2094802
4. Palavecino E. Rapid methods for detection of MRSA in clinical specimens. Methods Mol Biol. 2020:2069:29-45. doi:10.1007/978-1-4939-9849-4_2
Method Description
Describes how the test is performed and provides a method-specific reference
The GeneXpert Dx System automates and integrates sample purification, nucleic acid amplification, and detection of the target sequence using real-time polymerase chain reaction (PCR). The system uses single-use disposable cartridges that hold the PCR reagents and host the PCR process. Because the cartridges are self-contained, cross-contamination is minimized. The test utilizes automated PCR for qualitative detection of proprietary sequences for the staphylococcal protein A (spa) gene, the gene for methicillin resistance (mecA), and the staphylococcal methicillin-resistant Staphylococcus aureus /S aureus DNA cassette chromosome mec (SCCmec) inserted into the S aureus chromosomal attB site. The assay includes a sample processing control to ensure the sample was processed correctly and to monitor for the presence of inhibitors in the PCR reaction. A probe check control verifies reagent rehydration, PCR tube filling in the cartridge, probe integrity, and dye stability.(Package insert: Xpert SA Nasal Complete 300-8799. Cepheid; Rev H, 09/2019)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Monday through Friday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
- Authorized users can sign in to Test Prices for detailed fee information.
- Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
- Prospective clients should contact their account representative. For assistance, contact Customer Service.
Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.
CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
87641
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| MECPI | Methicillin Resistance Gene, Varies | 48813-0 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| MESCR | Specimen Source | 31208-2 |
| MEORG | Organism Identified by Client | In Process |
| MECPR | mecA Resistance Gene | 48813-0 |