%0 Journal Article
%T Characterisation of a novel AmpC beta-lactamase, DHA-33, resistant to inhibition by cloxacillin.
%A Findlay J
%A Poirel L
%A Cherkaoui A
%A Schrenzel J
%A Nordmann P
%J Diagn Microbiol Infect Dis
%V 109
%N 4
%D 2024 Aug 18
%M 38763036
%F 2.983
%R 10.1016/j.diagmicrobio.2024.116356
%X Plasmid-encoded DHA-type AmpCs have been extensively reported in Enterobacterales. The expression of the genes encoding these plasmid-mediated enzymes are inducible and these enzymes are capable of conferring resistance to a wide spectrum of beta-lactams including penicillins and broad-spectrum cephalosporins. The identification of infections caused by AmpC-producing bacteria is a necessity, both for infection control/epidemiology purposes and to inform treatment choices. A common testing method for AmpC production in the clinical laboratory setting is to supplement Mueller-Hinton agar plates used for antibiotic disk diffusion with cloxacillin, a potent inhibitor of AmpC enzymes. Here we describe a novel DHA variant, produced by a clinical Escherichia coli isolate, which is resistant to cloxacillin inhibition.