Patent ID: 7807403

Claim:
A method for determining whether a microorganism produces an AmpC β-lactamase comprising: a) admixing a culture of a microorganism with an effective amount of each of i) a β-lactam-containing antibiotic, ii) a β-lactamase inhibitor to which AmpC β-lactamase is resistant, and iii) a permeabilizing agent for the microorganism present in a non-growth-inhibiting microorganism-permeabilizing amount to form an assay culture, b) maintaining the assay culture under appropriate culture conditions and for a time period sufficient to determine the interaction of the microorganism with the AmpC β-lactamase resistant inhibitor and the antibiotic, and thereby determine the presence of AmpC β-lactamase, wherein significant growth of the microorganism or a distortion in a zone of inhibition indicates the production of an AmpC β-lactamase by the microorganism.