Pirazmonam is a potent anti-gram-negative monobactam that is differentiated from aztreonam by its high intrinsic activity against Ps. aeruginosa and good activity against Pseudomonas species. Pirazmonam has generally poor activity against gram-positive aerobic bacteria and anaerobic bacteria. Pirazmonam is a Trojan Horse molecule containing a b-lactam antibiotic that has been developed based on bacterial iron uptake systems. It features high structural similarity to aztreonam attached to a 3-hydroxy-4-pyridinone iron chelating group. Pirazmonam exhibited strong affinity to penicillin-binding protein 3 (PBP3) of Escherichia coli and moderate to negligible affinity to the other E. coli PBPs.