Device and method for detecting antibiotic-inactivating enzymes

A method for determining whether a microorganism produces an AmpC β-lactamase comprising the steps of:

• a) admixing a culture of a microorganism suspected of producing a β-lactamase that inactivates a β-lactam-containing antibiotic with
• i) an antibiotic-effective amount of a penicillin- or cephalosporin-type antibiotic,
• ii) an effective amount of a β-lactamase inhibitor to which AmpC β-lactamase is resistant present in an amount of about 5 to about 50 μg, and
• iii) a permeabilizing agent for the microorganism dissolved or dispersed in a carrier present in a non-growth-inhibiting microorganism-permeabilizing effective amount to form an assay culture;
• and
• b) maintaining that 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 antibacterial compound, and thereby determine the presence of an AmpC β-lactamase, wherein a positive test indicates the presence of an AmpC β-lactamase.

A method for determining whether a microorganism produces an AmpC β-lactamase comprising the steps of:

• a) admixing a culture of a microorganism suspected of producing a β-lactamase that inactivates a β-lactam-containing antibiotic with
• i) an antibiotic-effective amount of a penicillin- or cephalosporin-type antibiotic,
• ii) an effective amount of clavulanate, sulbactam or tazobactam present in an amount of about 10 to about 30 μg, and
• iii) a permeabilizing agent for the microorganism comprised of a buffer solution dissolved or dispersed in a carrier present in a non-growth-inhibiting microorganism-permeabilizing effective amount to form an assay culture, wherein said carrier is a solid carrier, said culture is provided on a solid growth medium, said β-lactam-containing antibiotic is provided on a solid support, and said admixing is by contacting said culture with said solid carrier and said antibiotic provided on a solid support;
• and
• b) maintaining that 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 antibacterial compound, and thereby determine the presence of an AmpC β-lactamase, wherein a positive test indicates the presence of an AmpC β-lactamase.