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Sputum Microbial Culture (with Antimicrobial Susceptibility Testing)

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

This test checks for bacteria or fungi in your sputum to identify infections and determine the best treatment.

Quick summary

["Helps diagnose respiratory infections and guide antibiotic choices."]

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

Key facts at a glance

LOINC
106048-2
Short code
O+P Aspirate Micro
Synonyms
O+P Aspirate Micro
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
microscopy-light
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 Is Sputum Culture Used For?

Sputum culture is primarily used to diagnose infections in the lungs, such as pneumonia, bronchitis, or tuberculosis. It helps doctors identify the specific type of germ causing your symptoms and choose the most effective treatment, whether that’s antibiotics, antifungals, or other therapies.

How Is the Test Performed?

You’ll cough into a sterile container, and the sample is sent to a lab. The lab grows the microorganisms from your sputum to identify them and, if applicable, test their response to different antibiotics.

Preparation and Sample Collection

No special preparation is needed, but you may be asked to rinse your mouth with water before coughing into the container. Avoid smoking or using cough suppressants before the test, as they can affect results.

When Are Results Ready?

Results typically take 3–10 days, depending on the lab and whether antimicrobial susceptibility testing is included. You’ll be notified when your results are available.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Identifying the exact germ causing your respiratory infection ensures targeted treatment, reducing unnecessary side effects from broad-spectrum antibiotics. It’s especially critical for chronic conditions like cystic fibrosis or weakened immune systems, where infections can be more severe.

Short name

Sputum Culture

Frequently asked questions

Why did my doctor order this test?
Your doctor may recommend a sputum culture if you have symptoms like persistent coughing, fever, or difficulty breathing, especially if you’ve tried antibiotics without improvement. It’s also used for monitoring chronic lung conditions or before surgery to prevent infections.
How long does it take to get results?
Results usually take 3 to 10 business days, but this can vary. If you need urgent answers, your doctor may discuss alternative tests or follow-up steps.
What if my sputum culture comes back negative?
A negative result means no obvious germs were found in your sample. However, other causes of your symptoms—like inflammation, allergies, or a viral infection—could still be present. Your doctor may recommend additional tests or repeat the culture if symptoms persist.
  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