Potentiation of #betalactam #antibiotics and β-lactam/β-lactamase inhibitor combinations against #MDR and #XDR #Pseudomonas aeruginosa using non-ribosomal #tobramycin–cyclam conjugates (J Antimicrob Chemother., abstract)

[Source: Journal of Antimicrobial Chemotherapy, full page: (LINK). Abstract, edited.]

Potentiation of β-lactam antibiotics and β-lactam/β-lactamase inhibitor combinations against MDR and XDR Pseudomonas aeruginosa using non-ribosomal tobramycin–cyclam conjugates

Temilolu Idowu, Derek Ammeter, Gilbert Arthur, George G Zhanel, Frank Schweizer

Journal of Antimicrobial Chemotherapy, dkz228, https://doi.org/10.1093/jac/dkz228

Published: 28 May 2019




To develop a multifunctional adjuvant molecule that can rescue β-lactam antibiotics and β-lactam/β-lactamase inhibitor combinations from resistance in carbapenem-resistant Pseudomonas aeruginosa clinical isolates.


Preparation of adjuvant was guided by structure–activity relationships, following standard protocols. Susceptibility and chequerboard studies were assessed using serial 2-fold dilution assays. Toxicity was evaluated against porcine erythrocytes, human embryonic kidney (HEK293) cells and liver carcinoma (HepG2) cells via MTS assay. Preliminary in vivo efficacy was evaluated using a Galleria mellonella infection model.


Conjugation of tobramycin and cyclam abrogates the ribosomal effects of tobramycin but confers a potent adjuvant property that restores full antibiotic activity of meropenem and aztreonam against carbapenem-resistant P. aeruginosa. Therapeutic levels of susceptibility, as determined by CLSI susceptibility breakpoints, were attained in several MDR clinical isolates, and time–kill assays revealed a synergistic dose-dependent pharmacodynamic relationship. A triple combination of the adjuvant with ceftazidime/avibactam (approved), aztreonam/avibactam (Phase III) and meropenem/avibactam enhances the efficacies of β-lactam/β-lactamase inhibitors against recalcitrant strains, suggesting rapid access of the combination to their periplasmic targets. The newly developed adjuvants, and their combinations, were non-haemolytic and non-cytotoxic, and preliminary in vivo evaluation in G. mellonella suggests therapeutic potential for the double and triple combinations.


Non-ribosomal tobramycin–cyclam conjugate mitigates the effect of OprD/OprF porin loss in P. aeruginosa and potentiates β-lactam/β-lactamase inhibitors against carbapenem-resistant clinical isolates, highlighting the complexity of resistance to β-lactam antibiotics. Our strategy presents an avenue to further preserve the therapeutic utility of β-lactam antibiotics.

Topic: antibiotics – pseudomonas aeruginosa – immunologic adjuvants – pharmaceutical adjuvants – aztreonam – ceftazidime – lactams – ribosomes – infection – tobramycin – meropenem – toxic effect – potentiation – avibactam – carbapenem resistance


© The Author(s) 2019. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please email: journals.permissions@oup.com.

This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Keywords: Antibiotics; Drugs Resistance; Carbapenem; Beta-lactams; Pseudomonas aeruginosa; Tobramycin; Aztreonam; Avibactam; Ceftazidime.


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Giuseppe Michieli

I am an Italian blogger, active since 2005 with main focus on emerging infectious diseases such as avian influenza, SARS, antibiotics resistance, and many other global Health issues. Other fields of interest are: climate change, global warming, geological and biological sciences. My activity consists mainly in collection and analysis of news, public services updates, confronting sources and making decision about what are the 'signals' of an impending crisis (an outbreak, for example). When a signal is detected, I follow traces during the entire course of an event. I started in 2005 my blog ''A TIME'S MEMORY'', now with more than 40,000 posts and 3 millions of web interactions. Subsequently I added an Italian Language blog, then discontinued because of very low traffic and interest. I contributed for seven years to a public forum (FluTrackers.com) in the midst of the Ebola epidemic in West Africa in 2014, I left the site to continue alone my data tracking job.