Multidrug Resistance: A Global Concern

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Multiple drug resistance among bacteria has become a global issue with a considerable impact on the mortality associated with infectious diseases. This book is a detailed compilation of available ...
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β-Lactamases as Major Mechanism of Resistance in Gram-Negative Bacteria

Pp. 210-226 (17)

Mariagrazia Perilli, Giuseppe Celenza, Cristina Pellegrini and Gianfranco Amicosante


β-lactamases are the major mechanism of resistance against β-lactam antibiotics among Gram-negative bacteria. On the basis of their amino acid sequence, β-lactamases are divided into four classes: A, B, C and D. This classification was first proposed by Ambler. The classes A, C and D include enzymes that hydrolyse their substrates by forming an acyl enzyme through an active site, whereas class B β-lactamases are metallo-enzymes which utilise one or two ions in their active sites. The massive use of expanded-spectrum cephalosporins, since the 1980s, has been conducive for the emergence of extended-spectrum β-lactamases (ESBLs) in the clinical setting, a group of enzymes capable of hydrolysing a wide range of expanded-spectrum β-lactams, including the oxyiminocephalosporins, but they are inactive against cephamicins and carbapenems. The emergence and widespread of ESBLs compromised the usefulness of carbapenems in clinical therapy leading to the emergence and diffusion of carbapenemases and in particular metallo-β-lactamases


β-lactamases, metalloenzymes, ESBL, cephamicins, carbapenems, oxyiminocephalosporins


Department of Biomedical Sciences and Technologies, University of L'Aquila, Italy