Genetic support of extended-spectrum β-lactamases

ABSTRACTGenes encoding extended-spectrum β-lactamases (ESBLs) have been reported in a variety of Gram-negative species, mostly in Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii. They are mostly either TEM or SHV derivatives, CTX-M-like enzymes—now emerging worldwide—or, less frequently, VEB, GES, and PER ESBLs. The mechanisms responsible for their acquisition are very diverse, and mostly are related to insertion sequences (ISs), transposons, class 1 integrons, and also sul1-type integrons containing the ISCR1 element. This diversity of genetic vehicles at the origin of these mobilisation/acquisition processes enhances the spread of ESBLs.