Monobactams are β-lactam compounds wherein the β-lactam ring is alone and not fused to another ring (in contrast to most other β-lactams, which have at least two rings). They work only against aerobic Gram negative bacteria (e.g., Neisseria, Pseudomonas ). The only commercially available monobactam antibiotic is aztreonam. Adverse effects to monobactams can include skin rash and occasional abnormal liver functions. They have no cross-hypersensitivity reactions with penicillin but like penicillins can trigger seizures in patients with history of seizures.