Activities of ceftazidime, ceftaroline, and aztreonam alone and combined with avibactam against isogenic Escherichia coli strains expressing selected single β-lactamases

Avibactam is a novel beta-lactamase inhibitor that restores the activity of otherwise hydrolyzed beta-lactams against Gram-negative bacteria expressing different classes of serine beta-lactamases. In the last decade, beta-lactam-avibactam combinations were tested against a variety of clinical isolates expressing multiple commonly encountered beta-lactamases. Here, we analyzed isogenic Escherichia coli strains expressing selected single beta-lactamase genes that were not previously tested or were not characterized in an isogenic background. The activities of ceftazidime, ceftaroline, and aztreonam alone and in combination with 4 mg/L of avibactam, as well as comparator agents, were assessed against a unique collection of isogenic strains of Escherichia coli carrying selected extended-spectrum, inhibitor-resistant, and/or carbapenem-hydrolyzing bla genes. When combined with avibactam, ceftazidime, ceftaroline, or aztreonam MICs were reduced for 91.4%, 80.0%, and 80.0% of isolates, respectively. The data presented add to our understanding of the microbiologic spectrum of these beta-lactams with avibactam and serve as a reference for further studies. Published by Elsevier Inc.