Clinics and Departments

Laboratory Services

Lab Dept:

Microbiology/Virology

Test Name:

MRSA DETECTION BY PCR

General Information

Lab Order Codes:

MRSP (Routine testing), SMRSP (Infection Prevention surveillance MRSA testing)

Synonyms:

MRSA PCR screen, Methicillin-resistant Staphylococcus aureus PCR screen; Surveillance MRSA PCR

CPT Codes:

87641 - Staphylococcus aureus, methicillin resistant, amplified probe technique

Test Includes:

Detection of MRSA from nasal swabs in patients at risk for nasal colonization by PCR (polymerase chain reaction).

Logistics

Lab Testing Sections:

Molecular Diagnostics, Mpls campus

Phone Number:

612-813-7013

Test Availability:

Specimens accepted daily, 24 hours

Turnaround Time:

24-48 hours

Special Instructions:

Requisition must state site of specimen and date/time of collection.

Specimen

Specimen Type:

Anterior nares

Container:

Swab transport medium

Volume:

One swab

Collection:

Anterior Nares

1. Insert swab, premoistened with sterile saline, approximately 1-2 cm into the nostril. (1/2 inch from edge of nares)
2.
Rotate the swab against the nasal mucosa approximately 5 times.
3.
Insert the same swab into the second nostril and repeat sampling as in steps 1 and 2.
4.
Place in swab transport medium.
5.
Label container and transport to the laboratory.

Transport/Storage:

Transport to the Microbiology Laboratory at room temperature. If a delay is anticipated, refrigerate specimen at 4 C. Specimens are stable at room temperature for 2 days and 5 days at refrigerated temperature (2 - 8 C).

Sample Rejection:

NP wire swab (green); unrefrigerated specimen(s) with a transit time exceeding 2 days after collection; improper source; improperly labeled specimen; external contamination. If an unacceptable specimen is received, the patient’s caregiver will be notified and another specimen will be requested before the specimen is discarded.

Interpretive

Reference Range:

Negative: No MRSA DNA detected, MRSA nasal colonization unlikely

Unresolved results due to PCR inhibition are inconclusive. Consider repeat collection if clinically indicated.

Significant Finding:

Positive: MRSA DNA detected, MRSA nasal colonization likely
Newly identified patients will be called to the patient’s caregiver.

Limitations:

● Blood, excessive nasal secretions/mucus, decongestants and substances used to relieve nasal dryness or irritation may inhibit PCR and give unresolved results.
● Negative results may occur from improper specimen collection, handling and storage or because the number of organisms in the specimen is below the analytical sensitivity of the test.
● Results should be used as an adjunct to nosocomial infection control efforts to identify MRSA nasal carriers. This test is not intended to identify patients with staphylococcal infection.
● A positive test result does not necessarily indicate the presence of viable organisms.
● Mutations or polymorphisms in primer or probe binding sites may affect new or unknown MRSA variants resulting in a false negative result.

Methodology:

Polymerase Chain Reaction (PCR)

References:

Baron, EJ and RB Thompson Jr, Specimen Collection, Transport, and Processing: Bacteriology In J. Versalovic, et al, (ed) Manual of Clinical Microbiology, 11th edition, American Society for Microbiology, Washington DC, pg 237

Miller, J. Michael (1999), A Guide To Specimen Management in Clinical Microbiology, American Society for Microbiology, Washington, D.C.

BD Max™ MRSA XT Assay (2014/01), Circular PO168(01), GeneOhm Sciences Canada, Inc, 2555 boul. Parc-Technologique, Quebec, Qc, Canada, G1P 4s4.

Updates:

9/1/2010: Transport time extended from 2 hours to 1 day.
11/30/2011: Updated availability from M-S to Daily. Changed sample storage, previously listed as 2-5 degrees C. BD reference for ACP updated. Transport extended from 1 day to 2 days @ room temp.
2/20/12: Changed from Critical value to Significant finding.
6/7/15: Changed significant finding Alert Value; added Surveillance MrSA PCR to synonyms; updated references.



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