title: Antibiofilm activity of certain phytocompounds and their synergy with fluconazole against Candida albicans biofilms.
abstract: OBJECTIVE
  The aim of this study was to evaluate four phytocompounds (cinnamaldehyde, citral, eugenol and geraniol) for their in vitro inhibitory activity against pre-formed biofilms of Candida albicans alone or in combination with fluconazole and amphotericin B. These compounds were also tested at subinhibitory concentrations for their ability to inhibit biofilm formation.
  
  
  METHODS
  The XTT reduction assay, light microscopy and scanning electron microscopy (SEM) were employed to determine the inhibitory effect of the test compounds on biofilms. A chequerboard method was used for combination studies.
  
  
  RESULTS
  Both clinical and reference strains of C. albicans (C. albicans 04 and C. albicans SC5314, respectively) displayed formation of strong biofilms. Pre-formed Candida biofilms showed ≥1024× increased resistance to antifungal drugs and 2× increased resistance to cinnamaldehyde and geraniol, but no increased tolerance of eugenol. The test compounds were more active against pre-formed biofilms than amphotericin B and fluconazole. At 0.5× MIC, eugenol and cinnamaldehyde were the most inhibitory compounds against biofilm formation. Light and electron microscopic studies revealed the deformity of three-dimensional structures of biofilms formed in the presence of sub-MICs of eugenol and cinnamaldehyde. The cell membrane appeared to be the target site of compounds in both planktonic and sessile C. albicans cells, as observed by SEM. Combination studies showed that synergy was highest between eugenol and fluconazole (fractional inhibitory concentration index = 0.14) against pre-formed biofilms of C. albicans SC5314.
  
  
  CONCLUSIONS
  Promising antibiofilm activity was displayed by eugenol and cinnamaldehyde, which also showed synergy with fluconazole in vitro. Further evaluation in in vivo systems is required to determine whether these findings can be exploited in treating biofilm-associated candidiasis.
authors.affiliation: Department of Agricultural Microbiology, Aligarh Muslim University, Aligarh, India.
authors.forename: Mohd Sajjad Ahmad
authors.initials: MS
authors.lastname: Khan
authors.forename: Iqbal
authors.initials: I
authors.lastname: Ahmad
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives* / Q000494:pharmacology; D000666:Amphotericin B / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002176:Candida albicans / Q000187:drug effects* / Q000254:growth & development / Q000648:ultrastructure; D004357:Drug Synergism; D005054:Eugenol / Q000494:pharmacology*; D015725:Fluconazole / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D010936:Plant Extracts / Q000494:pharmacology; D013194:Staining and Labeling / Q000379:methods; D013778:Tetrazolium Salts / Q000378:metabolism
chemical_list: D000935:Antifungal Agents; D010936:Plant Extracts; D013778:Tetrazolium Salts; C059087:2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-((phenylamino)carbonyl)-2H-tetrazolium hydroxide; D005054:Eugenol; D000171:Acrolein; D000666:Amphotericin B; D015725:Fluconazole; C012843:cinnamaldehyde