Phenotypic confirmation of extended-spectrum B-lactamases (ESBL) in clinical isolates of Escherichia coli and Klebsiella pneumoniae at the San Juan Veterans Affairs Medical Center.

Extended-spectrum Beta (beta)-lactamases (ESBLs) have emerged as an important mechanism of resistance to B-lactam antibiotics in gram-negative bacteria (GNB). They are enzymes that hydrolyze older B-lactam antibiotics as well as broad-spectrum cephalosporins and monobactams. ESBL producers have been reported in many bacteria but special attention has been paid to the ones in E.