This invention provides novel beta-lactamase inhibitors of the aryl- and heteroaryl-sulfonamidomethylphosphonate monoester class having nitrogen-based cations or quarternary ammomium groups. The compounds inhibit three classes of beta-lactamases and synergize the antibacterial effects of beta-lactam antibiotics (e.g., imipenem and ceftazimdime) against those micro-organisms normally resistant to the beta-lactam antibiotics as a result of the presence of the beta-lactamases.
