title: Synergistic activity of fosfomycin, β-lactams and peptidoglycan recycling inhibition against Pseudomonas aeruginosa.
abstract: To evaluate the interconnection between peptidoglycan (PG) recycling, fosfomycin susceptibility and synergy between fosfomycin and β-lactams in Pseudomonas aeruginosa METHODS: Fosfomycin MICs were determined by broth microdilution and Etest for a panel of 47 PAO1 mutants defective in several components of PG recycling and/or AmpC induction pathways. PAO1 fosfomycin MICs were also determined in the presence of a 5 mM concentration of the NagZ inhibitor PUGNAc. Population analysis of fosfomycin susceptibility and characterization of the resistant mutants that emerged was also performed for selected strains. Finally, fosfomycin, imipenem and fosfomycin + imipenem killing curves were assessed.
  
  
  
  Mutants defective in AmpG, NagZ or all three AmpD amidases showed a marked increase in fosfomycin susceptibility (at least two 2-fold dilutions with respect to WT PAO1). Moreover, PAO1 fosfomycin MICs were consistently reduced from 48 to 24 mg/L in the presence of a 5 mM concentration of PUGNAc. Fosfomycin hypersusceptibility of the ampG, nagZ and triple ampD mutants was also clearly confirmed in the performed population analysis, although the emergence of resistant mutants, through GlpT mutations, was not avoided. Synergy between fosfomycin and imipenem was evidenced for the WT strain, the AmpC-hyperproducing strain (triple AmpD mutant) and the NagZ and AmpG mutants in killing curves. Moreover, regrowth of resistant mutants was not evidenced for the combination.
  
  
  
  PG recycling inhibitors are envisaged as useful adjuvants in the treatment of P. aeruginosa infections with β-lactams and fosfomycin and therefore further development of these molecules is encouraged.
authors.affiliation: Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Palma (IdISPa), Palma de Mallorca, Spain.
authors.forename: Myriam
authors.initials: M
authors.lastname: Hamou-Segarra
authors.affiliation: Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Palma (IdISPa), Palma de Mallorca, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Zamorano
authors.affiliation: Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Grishma
authors.initials: G
authors.lastname: Vadlamani
authors.affiliation: Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Mitchell
authors.initials: M
authors.lastname: Chu
authors.affiliation: Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Palma (IdISPa), Palma de Mallorca, Spain.
authors.forename: Irina
authors.initials: I
authors.lastname: Sanchez-Diener
authors.affiliation: Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Palma (IdISPa), Palma de Mallorca, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Juan
authors.affiliation: Centro Nacional de Biotecnología (CNB-CSIC), Madrid, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Blazquez
authors.affiliation: School of Chemistry and Biochemistry, The University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Mitchell
authors.initials: M
authors.lastname: Hattie
authors.affiliation: School of Chemistry and Biochemistry, The University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Keith A
authors.initials: KA
authors.lastname: Stubbs
authors.affiliation: Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Brian L
authors.initials: BL
authors.lastname: Mark
authors.affiliation: Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases, Instituto de Investigación Sanitaria de Palma (IdISPa), Palma de Mallorca, Spain antonio.oliver@ssib.es.
authors.forename: Antonio
authors.initials: A
authors.lastname: Oliver
mesh_terms: D000117:Acetylglucosamine / Q000031:analogs & derivatives / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002473:Cell Wall / Q000187:drug effects* / Q000378:metabolism; D004357:Drug Synergism; D005578:Fosfomycin / Q000494:pharmacology*; D017353:Gene Deletion; D015378:Imipenem / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010091:Oximes / Q000378:metabolism; D010457:Peptidoglycan / Q000378:metabolism*; D048448:Phenylcarbamates / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D010091:Oximes; D010457:Peptidoglycan; D048448:Phenylcarbamates; C068836:N-acetylglucosaminono-1,5-lactone O-(phenylcarbamoyl)oxime; D005578:Fosfomycin; D015378:Imipenem; D000117:Acetylglucosamine