Aztreonam is a synthetic monocyclic beta-lactam antibiotic, with the nucleus based on a simpler monobactam isolated from Chromobacterium violaceum. Aztreonam is similar in action to penicillin. It inhibits mucopeptide synthesis in the bacterial cell wall, thereby blocking peptidoglycan crosslinking. It has a very high affinity for penicillin-binding protein 3 (PBP-3) and mild affinity for PBP-1a. Aztreonam binds the penicillin-binding proteins of gram-positive and anaerobic bacteria very poorly and is largely ineffective against them. Aztreonam is bactericidal but less so than some of the cephalosporins. Aztreonam has strong activity against susceptible gram-negative bacteria, including Pseudomonas aeruginosa. It has no useful activity against gram-positive bacteria or anaerobes. It is known to be effective against a wide range of bacteria including Citrobacter, Enterobacter, E. coli, Haemophilus, Klebsiella, Proteus, and Serratia species.
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