Monobactam

Monobactams are bacterially-produced monocyclic β-lactam antibiotics. The β-lactam ring is not fused to another ring, in contrast to most other β-lactams.

Monobactams are narrow-spectrum antibiotics effective only against (strictly or facultatively) aerobic Gram-negativebacilli, exhibiting a high level of resistance to beta-lactamases of these organisms. Due to their narrow spectrum, monobactams can be used to treat infections by susceptible bacteria without disrupting the patient's microbiota. Monobactams are nevertheless seldom used.

Aztreonam is the archetypal monobactam. Other monobactams include tigemonam, nocardicin A, carumonam and tabtoxin. An example of a monobactam that lacks antibiotic activity, but is used clinically for other purposes, is the cholesterol absorption inhibitor ezetimibe which is used to treat hypercholesterolemia.