Antibiotic Sensitivity Test

What is an antibiotic sensitivity test?

Antibiotics are medicines used to fight bacterial infections. There are different types of antibiotics. Each type is only effective against certain bacteria. An antibiotic sensitivity test can help find out which antibiotic will be most effective in treating your infection.

The test can also be helpful in finding a treatment for antibiotic-resistant infections. Antibiotic resistance happens when standard antibiotics become less effective or ineffective against certain bacteria. Antibiotic resistance can turn once easily treatable diseases into serious, even life-threatening illnesses.

Other names: antibiotic susceptibility test, sensitivity testing, antimicrobial susceptibility test

What is it used for?

An antibiotic sensitivity test is used to help find the best treatment for a bacterial infection. It may also be used to find out which treatment will work best on certain fungal infections.

Why do I need an antibiotic sensitivity test?

You may need this test if you have an infection that has been shown to have antibiotic resistance or is otherwise hard to treat. These include tuberculosis, MRSA, and C. diff. You may also need this test if you have a bacterial or fungal infection that is not responding to standard treatments.

What happens during an antibiotic sensitivity test?

The test is done by taking a sample from the infected site. The most common types of tests are listed below.

• Blood culture
  • A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial.
• Urine culture
  • You will provide a sterile sample of urine in a cup, as instructed by your health care provider.
• Wound culture
  • Your health care provider will use a special swab to collect a sample from the site of your wound.
• Sputum culture
  • You may be asked to cough up sputum into a special cup, or a special swab may be used to take a sample from your nose.
• Throat culture
  • Your health care provider will insert a special swab into your mouth to take a sample from the back of the throat and tonsils.

Will I need to do anything to prepare for the test?

There are no special preparations needed for an antibiotic sensitivity test.

Are there any risks to the test?

There is very little risk to having a blood culture test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

There is no risk to having a throat culture, but it may cause slight discomfort or gagging.

There is no risk to having a urine, sputum, or wound culture.

What do the results mean?

Results are usually described in one of the following ways:

• Susceptible. The tested medicine stopped the growth or killed the bacteria or fungus causing your infection. The medicine may be a good choice for treatment.
• Intermediate. The medicine may work at a higher dose.
• Resistant. The medicine did not stop the growth or kill the bacteria or fungus causing the infection. It would not be a good choice for treatment.

If you have questions about your results, talk to your health care provider.

Is there anything else I need to know about an antibiotic sensitivity test?

Incorrect use of antibiotics has played a big role in the rise in antibiotic resistance. Make sure you use antibiotics the right way by:

• Taking all doses as prescribed by your provider
• Only taking antibiotics for bacterial infections. They don't work on viruses, like colds and flu.

Learn more about laboratory tests, reference ranges, and understanding results.