Monobactam

Monobactams are monocyclic and bacterially-produced β-lactam antibiotics. The β-lactam ring is not fused to another ring, in contrast to most other β-lactams.[1] Monobactams are effective only against aerobic Gram-negative bacteria (e.g., Neisseria, Pseudomonas). Siderophore-conjugated monobactams show promise for the treatment of multi drug-resistant pathogens.[2]

Aztreonam. (The four-membered ring at the bottom is the β-lactam. There is a second thiazole ring, but it is not fused to the β-lactam ring.)

Tigemonam

Aztreonam is a commercially available monobactam antibiotic. Other examples of monobactams are tigemonam,[3] nocardicin A, and tabtoxin.

Adverse effects to monobactams can include skin rash and occasional abnormal liver functions.

Monobactam antibiotics exhibit no IgE cross-reactivity reactions with penicillin but have shown some cross reactivity with cephalosporins, most notably ceftazidime, which contains an identical side chain as aztreonam.[4] Monobactams can trigger seizures in patients with history of seizures, although the risk is lower than with penicillins.