Cefotaxime CTA 5 µg (5x 50 discs, Oxoid)

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

TEST PRINCIPLE
Filter paper discs impregnated with defined amounts 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 inhibition zones around the test discs are measured and compared with the clinical breakpoints for the different antibiotics tested to determine susceptibility (S - Susceptible at standard exposure, I - Susceptible with increased exposure, R - Resistant). The diameter of the inhibition zones corresponds to the susceptibility of the tested bacterial strain to the antibiotic concentration at the edge of the inhibition zone.

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, for example, with the MICRONAUT system. There are increasingly more and more precise clinical breakpoints for this method, meaning that at least since EUCAST 10.0 (2020), certain antibiotics can only be tested using agar dilution and no longer by agar diffusion (!). We would be happy to advise you on this and help you find the best solution for your needs.