aztreonam-avibactam

Overview

Aztreonam-avibactam (AZA) is a novel antibacterial combination therapy pairing aztreonam (ATM), a monobactam antibiotic, with avibactam (AVI), a non-β-lactam β-lactamase inhibitor. The combination received regulatory approval in the United States and Europe, with FDA approval granted in 2025, representing a significant advance in the treatment of multidrug-resistant (MDR) Gram-negative infections. aztreonam is notable for its intrinsic stability against metallo-β-lactamases (MBLs), a class of enzymes that hydrolyze and inactivate most β-lactam antibiotics including carbapenems. Avibactam complements this profile by inhibiting serine-based β-lactamases, including extended-spectrum β-lactamases (ESBLs), AmpC enzymes, and serine carbapenemases such as KPC and OXA-48-type enzymes, but does not inhibit MBLs. Together, aztreonam-avibactam covers a broad spectrum of resistance mechanisms, making it a critical therapeutic option against carbapenem-resistant Enterobacterales (CRE) and MBL-producing organisms that are otherwise extremely difficult to treat.

The clinical significance of aztreonam-avibactam is underscored by its activity against pathogens harboring New Delhi metallo-β-lactamase (NDM) and other MBLs, which have spread globally and rendered many existing antibiotic classes ineffective. By combining aztreonam's inherent MBL stability with avibactam's serine β-lactamase inhibition, the combination addresses co-resistance scenarios in which organisms produce both MBL and serine β-lactamase enzymes simultaneously — a pattern that undermines alternatives such as ceftazidime-avibactam used alone.

Focus of Latest Publications

Recent publications have positioned aztreonam-avibactam as a focal point of investigation in the context of MBL-producing Enterobacterales, carbapenem-resistant organisms, and challenging pathogens with complex resistance profiles.

A 2026 multicenter study published in the Journal of Clinical Microbiology (PMID: 42007819) evaluated the performance of aztreonam-avibactam susceptibility testing using gradient diffusion methods, reflecting the need for reliable and standardized diagnostic tools now that the drug has entered clinical practice in the U.S. and Europe. Accurate susceptibility testing is a prerequisite for appropriate therapeutic deployment, and this work addressed the practical laboratory challenges of implementing AZA testing across multiple sites.

In parallel, a study published in Antimicrobial Agents and Chemotherapy (PMID: 41891866) assessed the comparative in vitro efficacy of aztreonam-avibactam against 593 MBL-producing Enterobacterales collected in France in 2024, benchmarking it against other emerging agents including cefepime-taniborbactam, cefepime-zidebactam, and cefiderocol. This head-to-head comparison is particularly relevant given the limited therapeutic alternatives against MBL producers, and it positions aztreonam-avibactam alongside cefiderocol as one of the most active options in this setting.

Another 2026 study in Antimicrobial Agents and Chemotherapy (PMID: 41874381) examined the in vitro activity of aztreonam-avibactam against the Stenotrophomonas maltophilia complex, comparing it to aztreonam combined with ceftazidime-avibactam. This study highlighted the mechanistic rationale of the combination: aztreonam is stable to the L1 MBL produced by S. maltophilia, while avibactam inhibits the L2 serine β-lactamase. The combination of aztreonam with ceftazidime-avibactam had previously been used off-label to approximate this dual coverage before aztreonam-avibactam became a co-formulated, approved product, making this comparative data clinically instructive.

A further study published in Transactions of the Royal Society of Tropical Medicine and Hygiene (PMID: 41869915) underscored the epidemiological urgency in lower-middle-income settings, documenting an outstanding prevalence of NDM-producing carbapenem-resistant Enterobacterales in India and demonstrating exceptionally potent in vitro activity of both cefiderocol and aztreonam-avibactam against these isolates. The authors emphasized the immediate need for access to these agents in India, where NDM-mediated carbapenem resistance is a major public health threat.

Across these studies, aztreonam-avibactam consistently emerges as one of few agents retaining reliable activity against MBL-producing Enterobacterales, and its approval fills a long-standing therapeutic gap in the management of infections caused by organisms resistant to carbapenems, polymyxins, and earlier-generation β-lactam/β-lactamase inhibitor combinations.

Key Publications

May A multicenter performance evaluation of aztreonam-avibactam gradient diffusion susceptibility testing for Enterobacterales. (Journal of clinical microbiology, 2026, PMID 42007819): "Aztreonam-avibactam (AZA) is a new monobactam/beta-lactamase inhibitor combination that recently received regulatory approval in the United States (U.S.) and Europe."
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-avibactam (ATM-AVI), FDA approved in 2025, combines aztreonam (ATM; stable to L1 β-lactamase) with avibactam (AVI; an L2 β-lactamase inhibitor)."
May Comparative in vitro efficacy of aztreonam-avibactam and other alternatives (cefepime-taniborbactam, cefepime-zidebactam, and cefiderocol) against metallo-β-lactamase-producing Enterobacterales isolated in 2024 in France. (Antimicrobial agents and chemotherapy, 2026, PMID 41891866): "We evaluated the in vitro activity of aztreonam-avibactam and other agents against 593 metallo-β-lactamase (MBL)-producing Enterobacterales collected in France in 2024."
May Outstanding presence of New Delhi metallo-beta-lactamase in carbapenem-resistant Enterobacterales and exceptionally potent in vitro activity of cefiderocol and aztreonam-avibactam emphasises their immediate access in India. (Transactions of the Royal Society of Tropical Medicine and Hygiene, 2026, PMID 41869915): "Outstanding presence of New Delhi metallo-beta-lactamase in carbapenem-resistant Enterobacterales and exceptionally potent in vitro activity of cefiderocol and aztreonam-avibactam emphasises their immediate access in India."