aztreonam

Overview

Aztreonam is a synthetic monocyclic beta-lactam antibiotic (monobactam) first approved in the 1980s, notable for its narrow-spectrum activity exclusively targeting aerobic Gram-negative bacteria. Unlike penicillins and cephalosporins, aztreonam lacks the bicyclic ring structure of classical beta-lactams and is therefore non-cross-reactive in most patients with penicillin allergy. Its mechanism of action involves binding to penicillin-binding protein 3 (PBP3) in Gram-negative organisms, inhibiting cell wall transpeptidation and triggering bacterial lysis. Because aztreonam has no intrinsic activity against anaerobes or Gram-positive bacteria, it exerts minimal disruption on the anaerobic components of human gut flora, a property that distinguishes it from broader-spectrum beta-lactams and carries meaningful implications for colonization resistance.

Aztreonam is used clinically to treat serious infections caused by susceptible Gram-negative pathogens, including Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Stenotrophomonas maltophilia complex. Its utility has been substantially extended in the era of multidrug-resistant (MDR) pathogens through combination with beta-lactamase inhibitors. Aztreonam is intrinsically stable to metallo-beta-lactamases (MBLs) such as NDM, making it an important backbone for combination regimens against carbapenem-resistant Enterobacterales. Its contemporary research profile reflects this role: aztreonam is increasingly studied in partnership with inhibitors such as avibactam, nacubactam, and ceftazidime-avibactam to overcome complex resistance mechanisms including MBL co-production and PBP3 mutations.

Focus of Latest Publications

Recent publications highlight aztreonam as an active subject of investigation across several intersecting areas: novel beta-lactam/inhibitor combinations, the management of MDR Gram-negative infections, gut microbiome preservation, and clinical pharmacology in diverse populations.

Novel combination regimens with beta-lactamase inhibitors

A central theme in 2025–2026 literature is pairing aztreonam with next-generation beta-lactamase inhibitors to restore activity against MBL-producing organisms. The Integral-1 trial (PMID 42134354), a double-blind randomized phase 3 study published in The Lancet, evaluated aztreonam-nacubactam alongside cefepime-nacubactam against imipenem-cilastatin as the comparator for complicated urinary tract infections (cUTI) and acute uncomplicated pyelonephritis. This represents a pivotal efficacy and safety assessment of aztreonam combined with nacubactam — a novel diazabicyclooctane inhibitor active against serine-beta-lactamases — in a well-controlled clinical setting.

Parallel to this, Phase 1 pharmacokinetic studies (PMID 41973073) conducted in healthy Japanese male participants assessed the safety, tolerability, and pharmacokinetics of nacubactam administered either alone or in combination with cefepime or aztreonam (2 g per dose each, intravenously over 60 minutes for 7 days). These studies established foundational PK/PD data for the aztreonam-nacubactam combination in a Japanese population, supporting broader international development.

The combination of aztreonam with avibactam (aztreonam-avibactam, AZA) also featured prominently. A comparative in vitro study (PMID 41874381) assessed the activity of aztreonam-avibactam and aztreonam plus ceftazidime-avibactam against the Stenotrophomonas maltophilia complex — an intrinsically MDR pathogen. The study exploited the complementary inhibitory spectrum of aztreonam (stable to L1 metallo-beta-lactamase) and avibactam (an L2 serine-beta-lactamase inhibitor), rationalizing their pairing for this organism where both resistance mechanisms co-exist.

Resistance emergence and genomic determinants

A retrospective clinical and genomic analysis (PMID 41870042) at a tertiary cancer center examined ceftazidime-avibactam-resistant E. coli isolates collected between 2017 and 2024. The study investigated patient- and isolate-level factors associated with reduced susceptibility to the aztreonam/ceftazidime-avibactam (ATM/CZA) combination as well as aztreonam-avibactam. Oxford Nanopore Technologies long-read sequencing was employed to characterize genomic determinants of resistance, providing high-resolution insight into resistance gene context and mobile genetic elements. These findings are particularly relevant for oncology patients with Gram-negative infections, a population with high antibiotic exposure and elevated risk of resistance selection.

A complementary case-level study (PMID 41718487) described treatment optimization for a patient with MDR E. coli harboring both NDM metallo-beta-lactamase and PBP3 mutations — a combination that undermines both aztreonam monotherapy (via MBL hydrolysis of aztreonam's partner agents) and ceftazidime-avibactam alone (via PBP3 alteration reducing target engagement). Post-surgical administration of ceftazidime-avibactam combined with aztreonam was used, exploiting the MBL-stability of aztreonam and the serine-beta-lactamase inhibition provided by avibactam, illustrating the rational basis for such "hybrid" combinations.

Gut microbiome and colonization resistance

A murine model study (PMID 42224177) compared the microbiome impact of extended antibiotic courses. Notably, 5 or 10 days of aztreonam treatment did not alter colonization resistance, in stark contrast to piperacillin/tazobactam, which caused prolonged disruption of human gut flora even at shorter durations. This finding reinforces aztreonam's ecological advantage as a narrow-spectrum agent preserving anaerobic gut communities, relevant to infection prevention and antimicrobial stewardship decisions.

Contextual note on co-published research

One publication co-indexed in this dataset (PMID 41661672) concerns FASN inhibition in colorectal cancer and mentions ATM only in the context of the ATM kinase (ataxia-telangiectasia mutated) rather than aztreonam; it also involves BRCA1 pathway biology, PARP inhibitor olaparib, and TVB-2640 (a FASN inhibitor). While this publication does not involve aztreonam the antibiotic, its co-occurrence reflects database overlap between the abbreviation "ATM" (aztreonam) and the ATM kinase gene symbol.