Aztreonam (trade names Azactam injection, Cayston inhalation) is a monobactam antibiotic used primarily to treat infections caused by gram-negative bacteria. It is a synthetic drug based on a simpler monobactam isolated from Chromobacterium violaceum. It is resistant to some beta-lactamases, but is inactivated by extended-spectrum beta-lactamases. It was approved by the U.S. Food and Drug Administration (FDA) in 1986.