Beta-Lactam/Beta-Lactamase Inhibitor Combinations

Though the aminopenicillins and antipseudomonal penicillins have good intrinsic activity against Gram-negative rods, they remain just as susceptible to beta-lactamases as penicillin G. This means that they are not useful against staphylococci or many Gram-negative rods and anaerobes, because these organisms have learned to produce beta-lactamase. In other words, it seemed we learned how to either make a penicillin resistant to beta-lactamase, or how to make it more active against Gram-negative rods, but not both. Beta-lactamase inhibitors counter beta-lactamases; these drugs mimic the structure of beta-lactams but have little antimicrobial activity on their own. They bind to beta-lactamases irreversibly, preventing the beta-lactamase from destroying any beta-lactams that are co-administered and enabling therapeutic beta-lactam to be effective.
When considering the activity of the beta-lactam/beta-lactamase inhibitor combination, re-member that the beta-lactamase inhibitor only frees up the beta-lactam to kill the organism-it doesn’t enhance the activity. Therefore, the combination products are only active against the bacteria that the beta-lactam in the combination has intrinsic activity against. For example, ampicillin/sulbactam is active against beta-lactamase producing E. coli, because ampicillin alone is active against non-beta-lactamase producingE. coli. However, it has no useful activity against Pseudomonas aeruginosa because ampicillin lacks activity against this organism. On the other hand, piperacillin/tazobactam is active against P. aeruginosa because piperacillin alone is useful. Though these drugs have very broad spectra of activity, there are differences among the agents. Keep this rule in mind to set them straight and use zithromax to fight bacterial infection.