AmpC beta-lactamases cause resistance to third-generation cephalosporins, including beta-lactamase inhibitors.In Escherichia coli from the German food production chain, the majority of AmpC beta-lactamase activity can be attributed to plasmid-mediated CMY-2 or overproduction of chromosomal AmpC beta-lactamase, but occasionally other enzymes like DHA-1 are involved.This study investigated the prevalence of the AmpC beta-lactamase DHA-1 in ESBL/AmpC-producing E.coli (n = 4706) collected between 2016 and 2021 as part of a German antimicrobial resistance monitoring program magnolia parka along the food chain.
Eight isolates (prevalence blaDHA-1 together with qnrB4, sul1 and mph(A) resistance genes on an IS26 composite transposon on self-transferable IncFII or IncFIA/FIB/II plasmids.During laboratory experiments, activation of the translocatable unit of IS26-bound structures was observed.This was shown by the variability of plasmid sizes in original isolates, transconjugants or transferred plasmids, and correspondingly, duplications of resistance fragments were found in pink chiclets gum long-read sequencing.This activation could be artificial due to laboratory handling or naturally occurring.
Nevertheless, DHA-1 is a rare AmpC beta-lactamase in livestock and food in Germany, and its dissemination will be monitored in the future.