From the Research
The combination of ceftazidime, clavulanic acid, and aztreonam can be effective against certain resistant bacterial infections, particularly those caused by organisms producing extended-spectrum beta-lactamases (ESBLs) or metallo-beta-lactamases (MBLs), as evidenced by a study published in 2019 1. This combination works through complementary mechanisms:
- ceftazidime provides broad-spectrum activity against gram-negative bacteria,
- clavulanic acid inhibits many beta-lactamases that would otherwise inactivate ceftazidime,
- and aztreonam adds coverage against aerobic gram-negative bacteria while remaining stable against many beta-lactamases. For severe infections caused by resistant organisms, typical dosing might include ceftazidime 2g IV every 8 hours, combined with clavulanic acid (usually as part of amoxicillin-clavulanate) and aztreonam 2g IV every 6-8 hours, with treatment duration typically 7-14 days depending on infection site and severity. This combination is particularly useful for complicated infections where standard therapies have failed. However, this specific triple combination is not a standard regimen, and treatment should be guided by culture and sensitivity results. The rationale is that the three agents together can overcome multiple resistance mechanisms simultaneously, providing synergistic activity against difficult-to-treat pathogens, as supported by studies evaluating the synergy of ceftazidime-avibactam in combination with other antimicrobials, including aztreonam 2. Some studies have shown that the combination of aztreonam and amoxicillin-clavulanate has a synergistic effect on certain resistant isolates, including those producing class B and/or class D carbapenemases with or without extended-spectrum β-lactamases 1. It is essential to consider the potential for emergence of resistance when using these combinations, as highlighted in a study comparing clinical outcomes and emergence of resistance of Pseudomonas aeruginosa infections treated with ceftolozane-tazobactam versus ceftazidime-avibactam 3. In clinical practice, the choice of treatment should be guided by the results of susceptibility testing and the severity of the infection, with consideration of the potential benefits and risks of combination therapy, as noted in a study published in 2021 4. Key points to consider when using this combination include:
- Monitoring for signs of resistance and adjusting treatment accordingly
- Using the combination for complicated infections where standard therapies have failed
- Guiding treatment by culture and sensitivity results
- Considering the potential for emergence of resistance and taking steps to mitigate this risk. Overall, the combination of ceftazidime, clavulanic acid, and aztreonam can be a useful option for treating certain resistant bacterial infections, but its use should be guided by careful consideration of the potential benefits and risks, as well as the results of susceptibility testing and clinical experience, as supported by the most recent and highest quality study available 5.