Plates without AB-loading (5x 50 sheets, Oxoid)

BACKGROUND
Antibiotic susceptibility discs are used to determine the semi-quantitative susceptibility of common, fast-growing, and certain fastidious bacteria to antibiotics using the agar diffusion method.

TEST PRINCIPLE
Filter paper discs impregnated with defined quantities of antibiotics are applied to the surface of an appropriate medium (e.g., Mueller-Hinton agar). The culture medium must first be inoculated with a standardized inoculum (EUCAST recommendation: McFarland 0.5) of a fresh pure culture of the bacterial strain to be tested. After 24 hours of incubation, growth is checked, the zones of inhibition around the test discs are measured, and compared with the clinical breakpoints for the various antibiotics tested to determine susceptibility (S - Susceptible at standard exposure, I - Susceptible to increased exposure, R - Resistant). The diameter of the zones of inhibition corresponds to the susceptibility of the tested bacterial strain to the antibiotic concentration at the edge of the zone of inhibition. 

You can find various service documents, such as templates with inhibition zone limits for easy evaluation of the agar diffusion test and a collection of guidelines in our Media Library. Content and Storage:

·Cartridges with 50 test discs each
·Store at 2-8°C.

As an alternative to agar diffusion, we recommend agar dilution, which can be partially automated with systems such as the MICRONAUT system. There are increasingly more precise clinical breakpoints available for agar dilution, meaning that, at least since EUCAST 10.0 (2020), certain antibiotics can only be tested using agar dilution and no longer using agar diffusion (!). We would be happy to advise you on this and help you find the best solution.