Monobactam

Aztreonam
Drug class
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.)
Class identifiers
Use	Bacterial infection
ATC code	J01DF
External links
MeSH	D008997
Legal status
In Wikidata

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.¹

Monobactams are narrow-spectrum antibiotics² effective only against (strictly or facultatively³) aerobic Gram-negative bacilli,⁴⁵³ exhibiting a high level of resistance to beta-lactamases of these organisms.³ Due to their narrow spectrum, monobactams can be used to treat infections by susceptible bacteria without disrupting the patient's microbiota.² Monobactams are nevertheless seldom used.²

Aztreonam is the archetypal monobactam.⁶ Other monobactams include tigemonam,⁷ 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.⁸

Monobactams exert their antibacterial effects by binding to penicillin-binding proteins (PBPs), thereby inhibiting bacterial wall synthesis.⁵ Monobactams exhibit poor affinity for PBPs of Gram-positive bacteria as well as of strictly anaerobic bacteria, resulting in a lack of significant antimicrobial activity against these kinds of organisms.³ Monobactams are synergetic with aminoglycosides, and piperacillin.⁵

Bacterial resistance to monobactams have been observed, and is mediated by bacterial beta-lactamases.⁵

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.⁹ Monobactams can trigger seizures in patients with history of seizures, although the risk is lower than with penicillins.

Siderophore-conjugated monobactams show promise for the treatment of multi drug-resistant pathogens.¹⁰