Evaluation of a Double Synergy Differential Test (DSDT) for differential detection of ESBL and AmpC-type beta-lactamases in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis

This work describes a simple and practical double synergy differential test (DSDT) that couples the detection of ESBLsand AmpC-type enzymes by means of a combo-disk approach using cefotaxime and ceftazidime as indicator substrates,and clavulanate and boronic acid as enzyme inhibitors. The DSDT was tested with a collection of 118 Escherichiacoli, Klebsiella pneumoniae and Proteus mirabilis strains with different beta-lactamase profiles, and proved to be highlysensitive and specific for the detection of ESBL and AmpC-producing isolates.