GES: an emerging family of extended spectrum beta-lactamases

Extended-spectrum β-lactamases (ESBLs) are well known for their role in bacterial resistance to β-lactam antibiotics. They occupy a wide variety of geographical niches and occur almost freely in some nosocomial environments. Toward the very end of the 20th century, a novel family of ESBLs was described, called Guiana-Extended-Spectrum (GES), named after the country of origin of the first isolate, French Guiana. Once labeled as “obscure,” GES-type ESBLs have emerged in a variety of countries, with nine known variants and several documented outbreaks. Outstanding features of these class A ESBLs are the ability of certain members to hydrolyze carbapenems, difficulties experienced in reliablying identifying them in the clinical laboratory, problems arising due to unclear nomenclature, and the paucity of available clinical data.