Synergistic effects of inhaled aztreonam plus tobramycin on hypermutable cystic fibrosis Pseudomonas aeruginosa isolates in a dynamic biofilm model evaluated by mechanism-based modeling and whole genome sequencing

Siobhonne K J Breen; Marina Harper; Carla López-Causapé; Kate E Rogers; Jessica R Tait; Thomas R Smallman; Yinzhi Lang; Wee Leng Lee; Jieqiang Zhou; Yongzhen Zhang; Jurgen B Bulitta; Roger L Nation; Antonio Oliver; John D Boyce; Cornelia B Landersdorfer

doi:10.1016/j.ijantimicag.2024.107161

Synergistic effects of inhaled aztreonam plus tobramycin on hypermutable cystic fibrosis Pseudomonas aeruginosa isolates in a dynamic biofilm model evaluated by mechanism-based modeling and whole genome sequencing

Int J Antimicrob Agents. 2024 Mar 30:107161. doi: 10.1016/j.ijantimicag.2024.107161. Online ahead of print.

Authors

Affiliations

¹ Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia. Electronic address: Siobhonne.Breen@monash.edu.
² Biomedicine Discovery Institute, Department of Microbiology, Monash University, Melbourne, Victoria, Australia. Electronic address: Marina.harper@monash.edu.
³ Servicio de Microbiología, Hospital Universitario Son Espases-IdISBa, Palma de Mallorca, Spain; CIBER Enfermedades Infecciosas (CIBERINFEC), Madrid, Spain. Electronic address: carla.lopez@ssib.es.
⁴ Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia. Electronic address: Kate.Rogers@monash.edu.
⁵ Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia. Electronic address: Jess.Tait@monash.edu.
⁶ Biomedicine Discovery Institute, Department of Microbiology, Monash University, Melbourne, Victoria, Australia.
⁷ Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Orlando, Florida, USA. Electronic address: y.lang@cop.ufl.edu.
⁸ Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia. Electronic address: wee.lee@monash.edu.
⁹ Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Orlando, Florida, USA. Electronic address: zhou.jieqiang@cop.ufl.edu.
¹⁰ Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Orlando, Florida, USA. Electronic address: yongzhenzhang@cop.ufl.edu.
¹¹ Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Orlando, Florida, USA. Electronic address: jbulitta@ufl.edu.
¹² Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia. Electronic address: Roger.Nation@monash.edu.
¹³ Servicio de Microbiología, Hospital Universitario Son Espases-IdISBa, Palma de Mallorca, Spain; CIBER Enfermedades Infecciosas (CIBERINFEC), Madrid, Spain. Electronic address: antonio.oliver@ssib.es.
¹⁴ Biomedicine Discovery Institute, Department of Microbiology, Monash University, Melbourne, Victoria, Australia. Electronic address: john.boyce@monash.edu.
¹⁵ Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia. Electronic address: cornelia.landersdorfer@monash.edu.

PMID: 38561094
DOI: 10.1016/j.ijantimicag.2024.107161

Abstract

Hypermutable Pseudomonas aeruginosa strains are highly prevalent in chronic lung infections of patients with cystic fibrosis (CF). Acute exacerbations of these infections have limited treatment options. This study aimed to investigate inhaled aztreonam and tobramycin against clinical hypermutable P. aeruginosa strains using the CDC dynamic in vitro biofilm reactor (CBR), mechanism-based mathematical modeling (MBM) and genomic studies. Two CF multidrug-resistant strains were investigated in a 168h CBR (n=2 biological replicates). Regimens were inhaled aztreonam (75 mg 8-hourly) and tobramycin (300 mg 12-hourly) in monotherapies and combination. The simulated pharmacokinetic profiles of aztreonam and tobramycin (t_1/2=3h) were based on published lung fluid concentrations in patients with CF. Total viable and resistant counts were determined for planktonic and biofilm bacteria. MBM of total and resistant bacterial counts, and whole genome sequencing were completed. Both isolates showed reproducible bacterial regrowth and resistance amplification for the monotherapies by 168h. The combination performed synergistically, with minimal resistant subpopulations compared to the respective monotherapies at 168h. Mechanistic synergy appropriately described the antibacterial effects of the combination regimen in the MBM. Genomic analysis of colonies recovered from monotherapy regimens indicated noncanonical resistance mechanisms were likely responsible for treatment failure. The combination of aztreonam and tobramycin was required to suppress regrowth and resistance of planktonic and biofilm bacteria in all biological replicates of both hypermutable multidrug-resistant P. aeruginosa CF isolates. The developed MBM could be utilized for future investigations of this promising inhaled combination.

Keywords: Pseudomonas aeruginosa; combination therapy; dynamic biofilm model; hypermutator; mathematical modeling; resistance mechanisms.