Beta-lactamases and bacterial resistance to antibiotics.

The efficiency of beta-lactam antibiotics, which are among our most useful chemotherapeutic weapons, is continuously challenged by the emergence of resistant bacterial strains. This is most often due to the production of beta-lactamases by the resistant cells. These enzymes inactivate the antibiotics by hydrolysing the beta-lactam amide bond. The elucidation of the structures of some beta-lactamases by X-ray crystallography has provided precious insights into their catalytic mechanisms and revealed unsuspected similarities with the DD-transpeptidases, the bacterial enzymes which constitute the lethal targets of beta-lactams. Despite numerous kinetic, structural and site-directed mutagenesis studies, we have not completely succeeded in explaining the diversity of the specificity profiles of beta-lactamases and their surprising catalytic power. The solutions to these problems represent the cornerstones on which better antibiotics can be designed, hopefully on a rational basis.