Antibiotic susceptibility data

Antibiotic susceptibility tests (antibiograms) measure the sensitivity of a bacterial strain towards antibiotics in specific concentrations.

These tests are performed by the disc diffusion method. For this, a bacteria suspension is spread evenly across an agar plate and paper discs, each impregnated with a specific concentration of an antibiotic are laid onto it. The antibiotic diffuses from the paper into the surrounding agar creating a concentration gradient. The sensitivity of the bacterial strain against the tested antibiotic is measured through the diameter of the resulting inhibition zone, the area where no bacterial growth occurs) surrounding the paper disc.

Antibiotic sensitivity testing using the disc diffusion method

Strains showing larger inhibition zones are more sensitive to an antibiotic, smaller inhibition zones are indicative of greater resistance.

In BacDive the inhibition zone diameters are displayed in tables. The respective cultivation conditions that were applied can be found in the header (see screenshot below).

BacDive displays raw data

It is important to note that BacDive only displays raw data. No statistics were applied to this data and therefore the single diameters may deviate between tests.

Breakpoints, the inhibition zone diameters where a strain can be classified as resistant to an antibiotic, depend on many factors, including species, antibiotic concentration, and cultivation conditions. BacDive does not apply any breakpoints to antibiotic sensitivity data, only tests showing no visible inhibition (diameter = 0) are marked in red as resistant.

Example antibiotic susceptibility testing data in BacDive