ceftazidime-avibactam

Overview

Ceftazidime-avibactam is a combination antibacterial therapy consisting of the third-generation cephalosporin ceftazidime and the non-β-lactam β-lactamase inhibitor avibactam. It is designed to restore or enhance ceftazidime activity against many Gram-negative bacteria that produce β-lactamases, including some carbapenemase-producing Enterobacterales. Clinically, it is used for serious multidrug-resistant infections in settings where standard β-lactam therapy may be ineffective.

Its medical significance lies in its role as a targeted option for difficult-to-treat Gram-negative infections, particularly those caused by organisms such as Klebsiella pneumoniae, Enterobacter cloacae complex, and Pseudomonas aeruginosa. Because resistance can emerge through β-lactamase evolution, porin changes, efflux upregulation, or acquisition of metallo-β-lactamases such as NDM, ceftazidime-avibactam is often discussed alongside aztreonam, aztreonam-avibactam, cefiderocol, meropenem-vaborbactam, and imipenem/relebactam in the context of contemporary antimicrobial stewardship and resistance management.

Focus of Latest Publications

Recent studies have focused on ceftazidime-avibactam as a key therapy for multidrug-resistant Gram-negative infections and on the mechanisms that determine success, failure, or resistance. A multicenter U.S. study across 22 medical centers examined outcomes and the timing of initiation of ceftazidime-avibactam for MDR Gram-negative infections, highlighting that the impact of when therapy is started remains an important real-world question. The publication framed ceftazidime-avibactam as a crucial treatment option, but noted that timing-related effects on outcomes were still unclear.

Several studies addressed carbapenem-resistant Enterobacterales and the growing challenge of metallo-β-lactamase production. One report described ceftazidime-avibactam plus aztreonam use after surgery in a patient with multidrug-resistant Escherichia coli carrying NDM and PBP3 mutations, reflecting the clinical strategy of pairing aztreonam with ceftazidime-avibactam to address NDM-mediated resistance. Another study examined clinical and genomic determinants of emergent non-susceptibility to ceftazidime-avibactam plus aztreonam in ceftazidime-avibactam-resistant E. coli, emphasizing that increasing NDM prevalence has driven use of the combination aztreonam/ceftazidime-avibactam. These findings underscore the evolving role of aztreonam-based combinations when ceftazidime-avibactam alone is insufficient.

Comparative effectiveness was also explored. In a propensity-score-weighted cohort of patients with KPC-producing Enterobacterales infections, ceftazidime-avibactam and meropenem-vaborbactam were associated with similar 30-day mortality, suggesting broadly comparable outcomes in that setting. This type of comparison is clinically relevant because both agents are used for resistant Enterobacterales, but their activity profiles differ depending on the resistance mechanism.

Resistance surveillance and mechanistic studies further defined the limits of ceftazidime-avibactam activity. In a Tunisian intensive care unit, resistance prevalence in Pseudomonas aeruginosa was reported for ceftazidime-avibactam and ceftolozane-tazobactam, indicating that resistance to newer anti-pseudomonal β-lactam/β-lactamase inhibitor combinations is already present in some hospital settings. Another study investigated ceftazidime-avibactam resistance evolution in P. aeruginosa and linked resistance to amino acid substitutions in ampC and OXA β-lactamases, as well as mutations in regulatory genes that increase AmpC production and MexAB-OprM efflux pump expression. These mechanisms help explain cross-resistance concerns with other novel β-lactams.

Additional in vitro work compared aztreonam-avibactam with aztreonam plus ceftazidime-avibactam against the Stenotrophomonas maltophilia complex, noting that aztreonam plus ceftazidime-avibactam has been used as a surrogate for aztreonam-avibactam, although direct comparisons had been lacking. This line of research reflects the broader interest in avibactam-containing regimens for organisms with complex β-lactam resistance phenotypes.

Key Publications

• May Ceftazidime-avibactam for multidrug-resistant gram-negative infections: outcomes and timing of initiation across 22 U.S. medical centers. (Antimicrobial agents and chemotherapy, 2026, PMID 42138697): "Ceftazidime-avibactam (CAZ-AVI) is a crucial treatment for multidrug-resistant (MDR) gram-negative infections; however, the impact of treatment timing and outcomes in real-world practice remains unclear."
• May Prevalence and Resistance Patterns of Pseudomonas aeruginosa in a Tunisian Intensive Care Unit. (The American journal of tropical medicine and hygiene, 2026, PMID 41806369): "The prevalence of resistance of P. aeruginosa was 29.8% and 26.2% to ceftazidime-avibactam (CAV) and ceftolozane-tazobactam (C/T), respectively."
• May Optimizing target inactivation to treat multidrug-resistant Escherichia coli with NDM and PBP3 mutations: "going the extra mile". (Antimicrobial agents and chemotherapy, 2026, PMID 41718487): "After surgery, ceftazidime-avibactam/aztreonam was administered."
• May Clinical and genomic determinants associated with emergent ceftazidime-avibactam plus aztreonam non-susceptibility in ceftazidime-avibactam resistant Escherichia coli. (Antimicrobial agents and chemotherapy, 2026, PMID 41870042): "Ceftazidime-avibactam (CZA) has revolutionized care for carbapenem-resistant Enterobacterales infections, yet increasing New Delhi metallo-β-lactamase (NDM) prevalence has driven use of CZA plus aztreonam (ATM/CZA)."
• May Comparative in vitro activity of aztreonam-avibactam and aztreonam plus ceftazidime-avibactam against Stenotrophomonas maltophilia complex. (Antimicrobial agents and chemotherapy, 2026, PMID 41874381): "Aztreonam plus ceftazidime-avibactam (ATM-CZA) has been used as a surrogate for ATM-AVI, but direct comparisons between the two regimens are lacking."
• May Comparative outcomes of ceftazidime-avibactam versus meropenem-vaborbactam for KPC-producing Enterobacterales infections. (Antimicrobial agents and chemotherapy, 2026, PMID 41870149): "Thirty-day mortality was similar in a propensity-score-weighted cohort of 73 patients with KPC-producing Enterobacterales infections treated with ceftazidime-avibactam or meropenem-vaborbactam."
• May Ceftazidime-avibactam resistance evolution in Pseudomonas aeruginosa and implications for cross-resistance to other novel β-lactams. (Antimicrobial agents and chemotherapy, 2026, PMID 41940815): "Resistance was associated with amino acid substitutions in ampC and OXA β-lactamases, or mutations in regulatory genes conferring hyper-production of AmpC and MexAB-OprM efflux pumps."