Patent ID: 7291480

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