title: Effects of Iron Chelators on the Formation and Development of Aspergillus fumigatus Biofilm.
abstract: Iron acquisition is crucial for the growth of Aspergillus fumigatus. A. fumigatus biofilm formation occurs in vitro and in vivo and is associated with physiological changes. In this study, we assessed the effects of Fe chelators on biofilm formation and development. Deferiprone (DFP), deferasirox (DFS), and deferoxamine (DFM) were tested for MIC against a reference isolate via a broth macrodilution method. The metabolic effects (assessed by XTT [2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt]) on biofilm formation by conidia were studied upon exposure to DFP, DFM, DFP plus FeCl3, or FeCl3 alone. A preformed biofilm was exposed to DFP with or without FeCl3. The DFP and DFS MIC50 against planktonic A. fumigatus was 1,250 μM, and XTT gave the same result. DFM showed no planktonic inhibition at concentrations of ≤2,500 μM. By XTT testing, DFM concentrations of <1,250 μM had no effect, whereas DFP at 2,500 μM increased biofilms forming in A. fumigatus or preformed biofilms (P < 0.01). DFP at 156 to 2,500 μM inhibited biofilm formation (P < 0.01 to 0.001) in a dose-responsive manner. Biofilm formation with 625 μM DFP plus any concentration of FeCl3 was lower than that in the controls (P < 0.05 to 0.001). FeCl3 at ≥625 μM reversed the DFP inhibitory effect (P < 0.05 to 0.01), but the reversal was incomplete compared to the controls (P < 0.05 to 0.01). For preformed biofilms, DFP in the range of ≥625 to 1,250 μM was inhibitory compared to the controls (P < 0.01 to 0.001). FeCl3 at ≥625 μM overcame inhibition by 625 μM DFP (P < 0.001). FeCl3 alone at ≥156 μM stimulated biofilm formation (P < 0.05 to 0.001). Preformed A. fumigatus biofilm increased with 2,500 μM FeCl3 only (P < 0.05). In a strain survey, various susceptibilities of biofilms of A. fumigatus clinical isolates to DFP were noted. In conclusion, iron stimulates biofilm formation and preformed biofilms. Chelators can inhibit or enhance biofilms. Chelation may be a potential therapy for A. fumigatus, but we show here that chelators must be chosen carefully. Individual isolate susceptibility assessments may be needed.
authors.affiliation: California Institute for Medical Research, San Jose, California, USA Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA Department of Medical Microbiology, Faculty of Medicine, Istanbul University, Istanbul, Turkey.
authors.forename: Hasan
authors.initials: H
authors.lastname: Nazik
authors.affiliation: California Institute for Medical Research, San Jose, California, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Penner
authors.affiliation: California Institute for Medical Research, San Jose, California, USA Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA.
authors.forename: Jose A
authors.initials: JA
authors.lastname: Ferreira
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, California, USA.
authors.forename: Janus A J
authors.initials: JA
authors.lastname: Haagensen
authors.affiliation: California Institute for Medical Research, San Jose, California, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Cohen
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, California, USA.
authors.forename: Alfred M
authors.initials: AM
authors.lastname: Spormann
authors.affiliation: California Institute for Medical Research, San Jose, California, USA.
authors.forename: Marife
authors.initials: M
authors.lastname: Martinez
authors.affiliation: California Institute for Medical Research, San Jose, California, USA.
authors.forename: Vicky
authors.initials: V
authors.lastname: Chen
authors.affiliation: California Institute for Medical Research, San Jose, California, USA Division of Pulmonary and Critical Care Medicine, Stanford University, Stanford, California, USA.
authors.forename: Joe L
authors.initials: JL
authors.lastname: Hsu
authors.affiliation: California Institute for Medical Research, San Jose, California, USA Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA.
authors.forename: Karl V
authors.initials: KV
authors.lastname: Clemons
authors.affiliation: California Institute for Medical Research, San Jose, California, USA Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA stevens@stanford.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Stevens
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D001232:Aspergillus fumigatus / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D001565:Benzoates / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002712:Chlorides / Q000494:pharmacology; D000077588:Deferasirox; D000077543:Deferiprone; D003676:Deferoxamine / Q000494:pharmacology*; D005290:Ferric Compounds / Q000494:pharmacology; D007501:Iron / Q000378:metabolism; D007502:Iron Chelating Agents / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010933:Plankton / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D011728:Pyridones / Q000494:pharmacology*; D013172:Spores, Fungal / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D013778:Tetrazolium Salts; D014230:Triazoles / Q000494:pharmacology*
chemical_list: D000935:Antifungal Agents; D001565:Benzoates; D002712:Chlorides; D005290:Ferric Compounds; D007502:Iron Chelating Agents; D011728:Pyridones; D013778:Tetrazolium Salts; D014230:Triazoles; C059087:2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-((phenylamino)carbonyl)-2H-tetrazolium hydroxide; D000077543:Deferiprone; D007501:Iron; D003676:Deferoxamine; C024555:ferric chloride; D000077588:Deferasirox