Inhibitor-resistant TEM -lactamases: phenotypic, genetic and biochemical characteristics

β-Lactamases represent the main mechanism of bacterial resistance to β -lactam antibiotics. The recent emergence of bacterial strains producing inhibitor-resistant TEM (IRT) enzymes could be related to the frequent use of β-lactamase inhibitors such as clavulanic acid, sulbactam and tazobactam in hospitals and in general practice. The IRT β -lactamases differ from the parental enzymes TEM-1 or TEM-2 by one, two or three amino acid substitutions at different locations. This paper reviews the phenotypic, genetic and biochemical characteristics of IRT β-lactamases in an attempt to shed light on the pressures that have contributed to their emergence.