Ormetoprim and Sulfamethoxazole Isolate Minimum Inhibitory Concentration [Susceptibility]
This test measures the lowest concentration of the drug combination ormetoprim/sulfamethoxazole that stops a bacterial isolate from growing, helping determine whether the organism is susceptible to this antimicrobial.
["The ormetoprim/sulfamethoxazole MIC tells your care team how well this drug combination can inhibit the specific bacteria causing an infection."]
Key facts at a glance
- LOINC
- 73615-7
- Short code
- Ormetroprim+Sulfamethoxazole Islt MIC
- Synonyms
- Ormetroprim+Sulfamethoxazole Islt MIC
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- mic
- 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
What This Test Measures
The test determines the minimum inhibitory concentration (MIC), which is the smallest amount of ormetoprim/sulfamethoxazole that prevents visible growth of the isolated bacteria in the laboratory. The result is reported for a specific bacterial isolate rather than measured directly in your blood or other body fluid.
How the Sample Is Handled
A bacterial isolate is first cultured from a clinical specimen, such as urine, wound material, or another site of infection. That pure isolate is then exposed to a series of ormetoprim/sulfamethoxazole concentrations in the microbiology laboratory to determine the MIC.
How to Read the Result
Results are typically reported as a numeric MIC value and interpreted as susceptible, intermediate, or resistant according to published breakpoints. Interpretive categories are more useful to clinicians than the raw number alone, and breakpoints may differ by bacterial species and testing method.
Why the Combination Is Used
Ormetoprim and sulfamethoxazole are used together because the two agents block sequential steps in bacterial folate synthesis, which can enhance the antimicrobial effect. Testing the combination helps guide treatment selection for infections caused by susceptible organisms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Susceptibility testing guides antibiotic selection and helps avoid ineffective treatment. An MIC in the susceptible range suggests the organism is likely to respond to ormetoprim/sulfamethoxazole at appropriate therapeutic doses, while an intermediate or resistant result suggests another agent may be needed. Results should always be interpreted alongside the patient's clinical condition, infection site, and dosing considerations.
Short name
Ormetoprim/Sulfamethoxazole Isolate MIC
Frequently asked questions
Does this test measure drug levels in my body?
What does an MIC number mean?
Can the result change over time?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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