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Colistin Resistance Microbial Confirmation (Antimicrobial Susceptibility Test)

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

This test checks whether certain bacteria are resistant to colistin, a last-resort antibiotic used to treat serious infections caused by drug-resistant bacteria.

Quick summary

["Helps determine if your infection may require alternative treatments due to antibiotic resistance patterns."]

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

Key facts at a glance

LOINC
93701-1
Short code
Colistin res mcr-2 Islt/Spm Ql
Synonyms
Colistin res mcr-2 Islt/Spm Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
CPT
85610
SNOMED
396252006
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Matters

Colistin is used when other antibiotics fail, but resistance can develop over time. This test confirms whether bacteria in your sample have developed resistance to colistin, guiding appropriate treatment choices.

What to Expect Before the Test

No special preparation is needed unless your healthcare provider instructs otherwise. A healthcare professional will collect a sample (likely from blood, urine, or other body fluid depending on infection site).

How the Test Works

The test involves culturing bacteria from your sample and testing their response to colistin. If bacteria grow despite colistin exposure, resistance is confirmed.

What the Results Mean

Results indicate whether your bacteria are sensitive or resistant to colistin. Resistance may prompt a switch to alternative antibiotics or further investigation into infection source.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: serum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Resistance to colistin is critical because it limits treatment options for severe infections. Early detection helps prevent spread of resistant bacteria and guides targeted therapy to prevent treatment failures.

Short name

Colistin Resistance Confirmation

Frequently asked questions

Will I need to take antibiotics before this test?
No, but if you’ve recently taken antibiotics, your provider may need to adjust testing procedures. Always follow your healthcare team’s instructions for sample collection.
What if my bacteria test resistant to colistin?
Resistance means your infection may require a different antibiotic. Your provider will work with you to choose the best treatment based on your specific bacteria and infection type.
How long will it take to get results?
Results typically take 2–5 business days, depending on lab processing. Your provider will contact you once available.
  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