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Methicillin Resistance Detection by Probe-Based Assay (e.g., for *Staphylococcus aureus* or other *Staphylococcus* species)

Published: August 9, 2026Updated: August 16, 2026

This test checks whether certain bacteria, such as *Staphylococcus aureus*, are resistant to the antibiotic methicillin. Resistance is detected using a specialized DNA probe to identify genes (like *mecA*) that confer this trait.

Quick summary

["This test helps doctors determine if your infection may require alternative antibiotics to treat effectively."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
88251-4
Short code
mecA Bld Pos Ql Probe
Synonyms
mecA Bld Pos Ql Probe
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order this test if you have a suspected *Staphylococcus* infection (e.g., skin infections, surgical site infections, or bloodstream infections) and are being treated with or considered for methicillin-based antibiotics. It helps guide treatment decisions to avoid ineffective or overly broad antibiotic use.

How the Test Works

A small sample of your bacteria (often collected from a wound, blood, or other site) is analyzed using a molecular probe. The probe binds to a specific gene linked to methicillin resistance, allowing the test to detect resistance quickly and accurately.

Sample Collection and Preparation

A healthcare provider will collect a sample (e.g., swab, blood, or other bodily fluid) from the affected area. The sample is then processed in a lab to extract bacterial DNA, which is tested for the presence of resistance genes.

What to Expect After the Test

Results are typically available within 24 to 48 hours. Your doctor will discuss the findings with you and adjust your treatment plan if needed, such as switching to a different antibiotic if resistance is confirmed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Methicillin Resistance Probe Test

Frequently asked questions

What does a positive result mean?
A positive result means the bacteria in your sample carry genes that make them resistant to methicillin. This means your doctor may need to adjust your antibiotic treatment to one that works better against this type of infection.
How long does it take to get results?
Results are usually available within 24 to 48 hours, depending on lab processing times. Your doctor will contact you once the results are ready.
Can I take antibiotics before the test?
Yes, you may be prescribed antibiotics before the test if your infection is severe or spreading. However, taking antibiotics can affect the test results. Your doctor will guide you on whether to stop or adjust your medication before sample collection.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy