title: Repurposing as a means to increase the activity of amphotericin B and caspofungin against Candida albicans biofilms.
abstract: OBJECTIVE
  Biofilms of Candida species, often formed on medical devices, are generally resistant to currently available antifungal drugs. The aim of this study was to identify compounds that increase the activity of amphotericin B and caspofungin, commonly used antifungal agents, against Candida biofilms.
  
  
  METHODS
  A library containing off-patent drugs was screened for compounds, termed enhancers, that increase the in vitro activity of amphotericin B against Candida albicans biofilms. Biofilms were grown in 96-well plates and growth was determined by the cell titre blue assay. Synergy between identified enhancers and antifungal agents was further characterized in vitro using fractional inhibitory concentration index (FICI) values and in vivo using a worm biofilm infection model. In light of the application of these enhancers onto implants, their possible effect on the growth potential of MG63 osteoblast-like cells was assessed.
  
  
  RESULTS
  Pre-incubation of C. albicans biofilms with subinhibitory concentrations of the enhancers drospirenone, perhexiline maleate or toremifene citrate significantly increased the activity of amphotericin B or caspofungin (FICI  < 0.5) against C. albicans and Candida glabrata biofilms. Moreover, these enhancers did not affect the growth potential of osteoblasts. Interestingly, toremifene citrate also enhanced the in vitro activity of caspofungin in a mixed biofilm consisting of C. albicans and Staphylococcus epidermidis. Furthermore, we demonstrate synergy between toremifene citrate and caspofungin in an in vivo worm C. albicans biofilm infection model.
  
  
  CONCLUSIONS
  Our data demonstrate an in vitro and in vivo enhancement of the antibiofilm activity of caspofungin by toremifene citrate. Furthermore, our results pave the way for implant-related applications of the identified enhancers.
authors.affiliation: Centre of Microbial and Plant Genetics, CMPG, KU Leuven, Kasteelpark Arenberg 20, Box 2460, 3001 Heverlee, Belgium.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Delattin
authors.forename: Katrijn
authors.initials: K
authors.lastname: De Brucker
authors.forename: Katleen
authors.initials: K
authors.lastname: Vandamme
authors.forename: Els
authors.initials: E
authors.lastname: Meert
authors.forename: Arnaud
authors.initials: A
authors.lastname: Marchand
authors.forename: Patrick
authors.initials: P
authors.lastname: Chaltin
authors.forename: Bruno P A
authors.initials: BP
authors.lastname: Cammue
authors.forename: Karin
authors.initials: K
authors.lastname: Thevissen
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology*; D000736:Androstenes / Q000494:pharmacology; D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D017173:Caenorhabditis elegans / Q000382:microbiology; D002176:Candida albicans / Q000187:drug effects* / Q000502:physiology; D000077336:Caspofungin; D058492:Drug Repositioning; D004357:Drug Synergism; D054714:Echinocandins / Q000494:pharmacology*; D055666:Lipopeptides; D008826:Microbial Sensitivity Tests; D010006:Osteoblasts / Q000187:drug effects / Q000502:physiology; D010480:Perhexiline / Q000031:analogs & derivatives / Q000494:pharmacology; D017312:Toremifene / Q000494:pharmacology
chemical_list: D000736:Androstenes; D000935:Antifungal Agents; D054714:Echinocandins; D055666:Lipopeptides; D017312:Toremifene; D000666:Amphotericin B; D000077336:Caspofungin; C023470:perhexiline maleate; D010480:Perhexiline; C035144:drospirenone
keywords: antifungal agents; drug synergy; toremifene citrate; yeast