antibiotic-sensitivity-test
Reviewed
Also called: Antibiotic Susceptibility Test, Sensitivity Testing, Antimicrobial Susceptibility Test, Drug Resistance Testing, Culture and Sensitivity, C & S
This test helps find which antibiotic will be most effective against the bacteria or fungus causing your infection. It is often used when an infection may be resistant to standard antibiotics.
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
No special preparation is needed.
A sample is taken from the infected site. Common methods include blood draw from a vein, sterile urine collection, swab of a wound, coughing up sputum, or swabbing the back of the throat and tonsils.
Blood culture: slight pain or bruising at the needle site, usually brief. Throat culture: slight discomfort or gagging. Urine, sputum, and wound cultures have no physical risk.
Understanding results
Your results show how well different antibiotics worked against the bacteria or fungus in the lab. Your healthcare provider will use these results to choose the best treatment for you.
- Susceptible: The tested antibiotic stopped the growth or killed the bacteria or fungus. It may be a good choice for treatment. Limitation: Lab results do not guarantee clinical success; your provider will consider your overall health. Next step: Your provider may prescribe this antibiotic.
- Intermediate: The antibiotic may work at a higher dose or if taken more often. Limitation: Higher doses may increase side effects; your provider will weigh risks and benefits. Next step: Your provider may adjust the dose or frequency, or choose a different antibiotic.
- Resistant: The antibiotic did not stop the growth or kill the bacteria or fungus. It would not be a good choice for treatment. Limitation: Resistance means the antibiotic is unlikely to work; other options must be considered. Next step: Your provider will select a different antibiotic or a combination of medicines.
- 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
Your healthcare provider will discuss the results and recommend the most appropriate antibiotic treatment. Always take antibiotics exactly as prescribed and complete the full course.
- 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
U.S. National Library of Medicine: antibiotic-sensitivity-test