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 4º C. Specimens are stable at room temperature for 2 days and 5 days at refrigerated temperature (2 - 8º 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.