Aztreonam, sold under the brand name Azactam among others, is an antibiotic used primarily to treat infections caused by gram-negative bacteria such as Pseudomonas aeruginosa.

[2] Aztreonam inhibits cell wall synthesis by blocking peptidoglycan crosslinking to cause bacterial death.

Nebulized forms of aztreonam are used to treat infections that are complications of cystic fibrosis and are approved for such use in the EU and the US; they are also used off-label for non-CF bronchiectasis, ventilator-associated pneumonia, chronic obstructive pulmonary disease, mycobacterial disease, and to treat infections in people who have received lung transplants.

It is known to be effective against a wide range of bacteria including Citrobacter, Enterobacter, E. coli, Haemophilus, Klebsiella, Proteus, and Serratia species.

In the United States, the Food and Drug Administration (FDA) approved the inhalation form in February 2010, for the suppression of P. aeruginosa infections in people with cystic fibrosis.

[14] Reported side effects include injection site reactions, rash, and rarely toxic epidermal necrolysis.

Aztreonam binds the penicillin-binding proteins of Gram-positive and anaerobic bacteria very poorly and is largely ineffective against them.

[medical citation needed] Aztreonam is under consideration for human infections sustained by metallo-beta-lactamase (MBL)-producing gram-negative bacteria.

[18][19] The combination of aztreonam and avibactam has demonstrated to be active against 80% of MBL isolates reaching a clinical infection resolution in 80% of MBL-infected patients.