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. The following represents minimum inhibitory concentration (MIC) susceptibility data for a few medically significant microorganisms. Staphylococcus aureus 8 - >128 μg/ml
Staphylococcus epidermidis 8 - 32 μg/ml
Streptococcus pyogenes 8 - ≥128 μg/mlSynergism between aztreonam and arbekacin or tobramycin against P. aeruginosa has been suggested. Spectrum of activity
Acinetobacter anitratus, Escherichia coli, Pseudomonas aeruginosa, and Proteus mirabilis are generally susceptible to aztreonam, while some staphylococci, Staphylococcus aureus, Staphylococcus haemolyticus and Xanthomonas maltophilia are resistant to it. Furthermore, Aeromonas hydrophila, Citrobacter koseri (Citrobacter diversus), Pantoea agglomerans (Enterobacter agglomerans), Haemophilus spp. and Streptococcus pyogenes have developed resistance to aztreonam to varying degrees.Aztreonam can be safely used in patients with a penicillin or cephalosporin allergy (except for patients with a ceftazidime allergy as ceftazidime and aztreonam share a similar side chain). It is also frequently used as an alternative to aminoglycosides because is not ototoxic or nephrotoxic.Aztreonam use has been recently reconsidered for human infections sustained by metallo-beta-lactamase (MBL)-producing Gram-negative bacteria. In these circumstances aztreonam is combined with avibactam (ceftazidime/avibactam). 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. Administration
Aztreonam is poorly absorbed when given orally, so it must be administered as an intravenous or intramuscular injection (trade name Azactam), or inhaled (trade name Cayston) using an ultrasonic nebulizer.
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. This may include bone infections, endometritis, intra abdominal infections, pneumonia, urinary tract infections, and sepsis. It is given by intravenous or intramuscular injection  or by inhalation.Common side effects when given by injection include pain at the site of injection, vomiting, and rash. Common side effects when inhaled include wheezing, cough, and vomiting. Serious side effects include Clostridium difficile infection and allergic reactions including anaphylaxis. Those who are allergic to other β-lactam have a low rate of allergy to aztreonam. Use in pregnancy appears to be safe. It is in the monobactam family of medications. Aztreonam inhibits cell wall synthesis by blocking peptidoglycan crosslinking to cause bacterial death.Aztreonam was approved for medical use in the United States in 1986. It was removed from the World Health Organizations List of Essential Medicines in 2019. It is available as a generic medication. It is a manufactured version of a chemical from the bacterium Chromobacterium violaceum. Medical uses
Nebulized forms of aztreonam are used to treat infections that are complications of cystic fibrosis and are approved for such use in Europe 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.Aztreonam has strong activity against susceptible Gram-negative bacteria, including Pseudomonas aeruginosa. It is resistant to some beta-lactamases, but is inactivated by extended-spectrum beta-lactamases.