Characterization of HMRZ-86: a novel chromogenic cephalosporin for the detection of extended-spectrum beta-lactamases.

Sir, HMRZ-86 is a new chromogenic cephalosporin. A carboxypropyloxyimino group bonded to the side chain at position 7 in the compound (Figure 1) protects the β-lactam ring from a range of β-lactamases, but not from extended-spectrum β-lactamases (ESBLs) or metallo-β-lactamases. 1 Hydrolysis of the β-lactam ring by these enzymes changes the wavelength absorbed by the conjugated double bond located at position 3, shifting the colour of the compound from yellow to red, in much the same way as occurs with nitrocefin. 2 In this study, we determined the usefulness of the com