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

beta-Lactamases represent the main mechanism of bacterial resistance to bet a-lactam antibiotics. The recent emergence of bacterial strains producing i nhibitor-resistant TEM (IRT) enzymes could be related to the frequent use o f beta-lactamase inhibitors such as clavulanic acid, sulbactam and tazobact am in hospitals and in general practice. The IRT beta-lactamases differ fro m the parental enzymes TEM-1 or TEM-2 by one, two or three amino acid subst itutions at different locations. This paper reviews the phenotypic, genetic and biochemical characteristics of IRT beta-lactamases in an attempt to sh ed light on the pressures that have contributed to their emergence.