Antibiotic Sensitivity Test
Reviewed
Also called: Antibiotic Susceptibility Test, Sensitivity Testing, Antimicrobial Susceptibility Test, Drug Resistance Testing, Culture and Sensitivity, C & S
An antibiotic sensitivity test can help find out which antibiotic will be most effective in treating your infection.
Specimen: Blood, urine, wound swab, sputum, or throat swab
Why this test may be ordered
- To find the best antibiotic treatment for a bacterial or fungal infection
- When an infection is suspected to be antibiotic-resistant, such as tuberculosis, MRSA, or C. diff
Preparation and collection
There are no special preparations needed for an antibiotic sensitivity test.
To find out what type of bacteria or fungi you have, your provider may order a fungal or bacteria culture. The test is done by taking a sample from the infected site. Your sample will be tested against different antibiotics to see if they are effective in killing the germs causing your infection.
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.
Understanding results
Your results will show how effective different antibiotics were in killing the bacteria or fungus causing your infection.
- Susceptible: The tested antibiotic stopped the growth or killed the bacteria or fungus causing your infection, so it may be a good choice for treatment. Limitation: Make sure to finish all of the antibiotics. Next step: Talk with your provider or pharmacist if you have any questions about your antibiotics.
- Intermediate: The antibiotic may work at a higher dose, or you may need to take the dose more often. Limitation: Take them exactly as your provider tells you. Next step: If you have questions about your results, talk to your provider.
- Resistant: The antibiotic did not stop the growth or kill the bacteria or fungus causing the infection. It would not be a good choice for treatment. Limitation: With antibiotic resistance, some diseases that were once easily treated can become serious or even life-threatening. Next step: If your results are resistant to all of the medicines, you may need to take a few medicines that may work better together.
- Results are based on lab conditions and may not perfectly predict how the antibiotic will work in your body.
- If all tested antibiotics are resistant, you may need a combination of medicines.
What to do next
If you have questions about your results, talk to your provider.
- What does my result mean for my treatment?
- Are there any side effects I should watch for?
- How should I take this antibiotic?
- Should I avoid any other medicines or foods while on this antibiotic?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: Antibiotic Sensitivity Test