Gram Stain of Tissue
This test examines the microscopic appearance of tissue samples under a microscope after staining with a Gram dye. It helps identify the presence of bacteria or other microorganisms by differentiating their cell wall structure.
["A Gram stain helps doctors diagnose infections by showing whether bacteria are Gram-positive or Gram-negative."]
Key facts at a glance
- LOINC
- 6664-7
- Short code
- Gram Stn Tiss
- Synonyms
- Gram Stn Tiss
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- gram-stain
- 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 a Gram Stain Used For?
A Gram stain is primarily used to identify bacterial presence in tissue samples. It’s a quick and simple test that can guide treatment decisions, especially in cases of suspected infection. Doctors may order this test when they suspect bacterial infections in wounds, abscesses, or other tissues.
How Is the Test Performed?
A small sample of tissue is collected (often from a biopsy) and prepared on a microscope slide. The tissue is stained with crystal violet and iodine, followed by alcohol, and then counterstained with safranin. The stained sample is then viewed under a microscope to observe bacterial morphology.
When Might You Need This Test?
You might need a Gram stain if you have symptoms like redness, swelling, or pus in a wound, unexplained fever, or signs of infection in a biopsy sample. It’s also used in research or diagnostic settings where identifying bacteria is critical.
What Are the Limitations?
While useful for identifying bacteria, a Gram stain does not provide detailed information about bacterial species, antibiotic resistance, or viral/bacterial counts. It’s often used alongside other tests for a complete diagnosis.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Gram stains play a vital role in quickly narrowing down potential bacterial infections. The results can help doctors choose appropriate antibiotics or confirm whether an infection is bacterial (and thus treatable with antibiotics) or something else (like a fungal or viral infection). This rapid feedback can influence treatment decisions and improve patient outcomes.
Short name
Tissue Gram Stain
Frequently asked questions
How long does it take to get results from a Gram stain?
Can a Gram stain detect viruses or fungi?
Is there any pain or discomfort associated with the tissue sample collection?
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