Novel GES/IBC extended-spectrum β-lactamase variants with carbapenemase activity in clinical enterobacteria

Two clinical isolates, an Escherichia coli and a Klebsiella pneumoniae, with decreased Susceptibility to carbapenems were studied. This phenotype was associated with production of novel GES/IBC variant beta-lactamases, designated GES-3 (from E. coli) and GES-4 (from K pneumoniae), exhibiting carbapenemase activity. Both enzymes possessed Ser at Ambler's position 170 instead of Gly found in the beta-lactamases GES-1 and IBC-1 that lack carbapenemase activity. Additionally, position 104 in GES-4 was occupied by a Lys as in IBC-1. bla(GES-3) and bla(GES-4) Occurred as gene cassettes in the variable regions of class I integrons carried by plasmids. The structure of the GES-4-encoding integron was similar to that of previously described IBC-1 integrons. The GES-3-encoding integron was. most likely. truncated at the 3' conserved segment. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.