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Colistin Resistance in Gram-Negative Bacteria (Qualitative, Culture-Based)

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

This test checks whether certain bacteria found in your sample are resistant to colistin, a broad-spectrum antibiotic used to treat infections caused by resistant bacteria.

Quick summary

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

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

Key facts at a glance

LOINC
100910-9
Short code
Gram neg colistin resist Stl Cult
Synonyms
Gram neg colistin resist Stl Cult
Category
chemistry
Sample
stool
Container
Clean container
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
organism-specific-culture
CPT
85610
SNOMED
396252006
Specimen volume
5 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

What This Test Measures

Colistin resistance is identified through bacterial culture and testing. A sample of your bodily fluid or tissue is grown in a lab to isolate bacteria, then exposed to colistin. If bacteria survive and grow despite colistin exposure, the result indicates resistance.

Why It Matters in Your Health

Colistin-resistant bacteria can be harder to treat with standard antibiotics. This test helps healthcare providers choose the most effective treatment for your infection, potentially preventing further spread of resistant bacteria.

Sample Collection and Preparation

A sample (such as blood, urine, or other bodily fluid) will be collected by your healthcare provider. The sample is then sent to a lab where bacteria are cultured and tested for colistin resistance.

When You Might Need This Test

This test is typically ordered if you have an infection caused by Gram-negative bacteria, especially if you’ve been exposed to colistin or other antibiotics, or if infections are recurring or resistant to standard treatments.

Reference range

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

Specimen: stool

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.

Clinical Significance

Short name

Colistin Resistance Screening

Frequently asked questions

How long will I need to wait for results?
Results are usually available within 3 to 5 business days, depending on the lab’s processing time. Your healthcare provider will discuss the results with you during your follow-up visit.
What does a positive result mean?
A positive result means the bacteria in your sample are resistant to colistin. This may require your doctor to adjust your antibiotic treatment plan to one that targets resistant bacteria more effectively.
Can I take antibiotics before this test?
It’s important to inform your healthcare provider about any antibiotics you’ve taken recently, as this can affect test results. Follow their instructions on when to stop antibiotics before testing if applicable.
  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