The AmpC phenotype in Norwegian clinical isolates of Escherichia coli is associated with an acquired ISEcp1-like ampC element or hyperproduction of the endogenous AmpC

Abstract

This is the first molecular study of Norwegian clinical E. coli isolates with an AmpC phenotype. Resistance was mediated either by expression of bla(CMY) from acquired ISEcp1-like-bla(CMY) elements, or by mutations or insertions in the chromosomal ampC gene control region leading to hyperproduction of the endogenous AmpC enzyme. There was no correlation between the level of ampC mRNA and the MICs of cephalosporins.