HomeLab TestsAntibiotic Sensitivity Test
Back to Lab Tests
Antibiotic Sensitivity Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Antibiotic Sensitivity Test

An antibiotic sensitivity test determines which specific medications will be most effective in treating a bacterial or fungal infection.

Overview

Antibiotics are designed to fight bacterial and certain fungal infections, but they are not effective against viruses. Because different antibiotics target specific types of germs, an antibiotic sensitivity test (also known as an antimicrobial susceptibility test) is used to identify the most effective treatment for your specific infection.

This test is also vital for identifying antibiotic-resistant infections. Antibiotic resistance occurs when bacteria change and resist the effects of standard medications, making once-treatable diseases potentially life-threatening.

Why do I need this test?

You may need this test if you have a bacterial or fungal infection that is suspected of being antibiotic-resistant. Examples include MRSA, tuberculosis, and C. diff.

What happens during the test?

Your provider will collect a sample from the site of the infection to identify the specific bacteria or fungi present. Common collection methods include:

  • Blood culture: A blood sample is drawn from a vein in your arm.
  • Urine culture: You provide a sterile urine sample in a cup.
  • Wound culture: A special swab is used to collect a sample from the wound site.
  • Sputum culture: You cough up mucus (phlegm) into a cup, or a nasal swab is used.
  • Throat culture: A swab is used to collect a sample from the back of the throat and tonsils.

The laboratory then tests your sample against various antibiotics to see which ones successfully kill the germs.

Understanding Results

Results are typically categorized as follows:

  • Susceptible: The antibiotic successfully stopped the growth or killed the germ, making it a good treatment choice.
  • Intermediate: The antibiotic may work if used at a higher dose or more frequently.
  • Resistant: The antibiotic failed to stop the growth or kill the germ and is not a suitable treatment choice.

Preventing Antibiotic Resistance

To ensure antibiotics remain effective, it is essential to use them correctly:

  • Take antibiotics exactly as prescribed and finish the entire course.
  • Do not use antibiotics for viral infections like the cold or flu.
  • Never share antibiotics or save them for later use.
  • Consult your pharmacist regarding the safe disposal of leftover medication.

Frequently Asked Questions

Ideally, you should not start any antibiotics until after the sample is taken, because early treatment can reduce the number of organisms and give a false‑negative culture. If you’re already on antibiotics, tell your clinician; sometimes the test can still be done, but the interpretation may be limited.
“Intermediate” indicates the antibiotic may work at higher doses, in the infection site where drug concentrations are higher, or when the organism is not highly resistant. Clinicians may still use an intermediate drug if it’s the best option, but they often prefer a “susceptible” agent or adjust the dose and duration accordingly.
Most labs report results within 24‑48 hours for common bacteria after the culture grows. For slower‑growing organisms (e.g., Mycobacterium tuberculosis) it can take several weeks. Your provider will usually call or update you as soon as the report is finalized.
Your provider will review the susceptibility profile and select an alternative antibiotic that the organism is susceptible to. In some cases, combination therapy or a newer drug class may be needed. The doctor may also consider the infection’s severity, site, and your medical history before finalizing the regimen.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

kontakt@hittavard.se

Ⓒ 2024. Alla rättigheter förbehålls av juxt ab

Sök
Om ossVillkor och policyVanliga frågorKontakta oss