A bacterial enzyme (penicillin amido-β-lactam hydrolase, EC184.108.40.206) that will hydrolyse *β-lactam antibiotics thereby conferring resistance; competitively inhibited by clavulanic acid. Extended-spectrum β-lactamases (ESBLs) will degrade the extended spectrum cephalosporins (e.g. cefuroxime, cefotaxime, and ceftazidime) and are an increasing problem. ESBLs have been reported for E. coli, Klebsiella, Enterobacter, Proteus, Pseudomonas, Salmonella, and Serratia and more than 170 different ESBLs were known by 2007. Most are still inhibited by clavulanic acid but unfortunately many are carried on plasmids that also carry genes for resistance to aminoglycosides, tetracycline, chloramphenicol, and fluoroquinolones.
Subjects: Chemistry — Medicine and Health.