This Kit consists of four cartridges of disc diffusion tablets: one cartridge of tablets with Cefotaxime, one with Ceftazidime and two cartridges of the cephalosporins combined with Cloxacillin (AmpC inhibitor).
If an organism is suspected of AmpC activity, it can be shown by a difference in the inhibition zone of the cephalosporin(s) alone and in combination with the inhibitor.
Interpretation
The results are interpreted by comparing the inhibition zones of the different tablets.
1) Compare the zone of inhibition of Cefotaxime 30 μg and Ceftazidime 30 μg tablet to the zones of inhibition of Cefotaxime 30 μg + Cloxacillin and Ceftazidime 30 μg + Cloxacillin tablets, respectively. If these zones are within 3mm of each other, record the organism as not expressing AmpC activity.
2) Measure the inhibition zones around Cefotaxime 30 μg + Cloxacillin (CTXCX) and Ceftazidime 30 μg + Cloxacillin (CAZCX), and compare with the respective zones around Cefotaxime 30 μg (CTX30) and Ceftazidime 30 μg (CAZ30). If one or both of the combination discs show zones ≥ 5mm than the single discs, the organism is demonstrating AmpC activity.
