Evolution of beta-lactamase inhibitors.

Beta-lactamase, the bacterial enzyme that can inactivate penicillins, cephalosporins and related antibiotics, can function outside the cell or in the periplasmic space. This resistance can be transferred between bacteria of the same or different species. Most strains of Staphylococcus aureus, Staphylococcus epidermidis, Klebsiella, Enterobacter, Pseudomonas aeruginosa and Bacteroides species are beta-lactamase producers. Clavulanic acid is a beta-lactamase inhibitor that works by blocking the enzyme center. When it is combined with amoxicillin and ticarcillin, it expands those drugs' spectrum of activity to bacteria that are resistant to the single antibiotics as well as to anaerobic bacteria.