Aztreonam (Synonyms: SQ 26,776)

Aztreonam (SQ-26) is a synthetic monocyclic beta-lactam antibiotic, which has a very high affinity for penicillin-binding protein 3 (PBP-3).

Aztreonam (SQ-26) is a synthetic monocyclic beta-lactam antibiotic (a monobactam), with the nucleus based on a simpler monobactam isolated from Chromobacterium violaceum. It was approved by the U.S. Food and Drug Administration in 1986. It is resistant to some beta-lactamases, but is inactivated by extended-spectrum beta-lactamases. Aztreonam has no useful activity against gram-positive or anaerobic microorganisms[1]. Aztreonam (SQ-26) is similar in action to penicillin. It inhibits mucopeptide synthesis in the bacterial cell wall, thereby blocking peptidogly can crosslinking. It has a very high affinity for penicillin-binding protein 3 (PBP-3) and mild affinity for PBP-1a. Aztreonam (SQ-26) binds the penicillin-binding proteins of gram-positive and anaerobic bacteria very poorly and is largely ineffective against them. Aztreonam (SQ-26) is bactericidal but less so than some of the cephalosporins[2].

References:
[1]. Kobayashi Y, et al. Synergy with aztreonam and arbekacin or tobramycin against Pseudomonas aeruginosa isolated from blood. J Antimicrob Chemother. 1992 Dec;30(6):871-2.
[2]. Guay DR, et al. Aztreonam, a new monobactam antimicrobial. Clin Pharm. 1985 Sep-Oct;4(5):516-26.