Candida albicans planktonic and sessile cells treated with biosynthesized silver nanoparticles.

IVANA L GALERA; MARÍA G PARAJE; MELISA A QUINTEROS; PAULINA L PÁEZ.

San Luis

Congreso; XIII Congreso Argentino de Microbiología General.; 2018

SAMIGE

Candidaalbicans is anormal commensal of the gastrointestinal microbiota in healthy individuals; however, as anopportunistic pathogen, is the most common etiological agent of candidiasis. C.albicans has the ability to form biofilms and morphogenetic conversionsbetween yeast and hyphal morphologies contribute to biofilm development and representan essential virulence factor. These attached communities of cells aresurrounded by a protective exopolymeric matrix that effectively shelters Candidaagainst the action of antifungals (ATFs). As fungi are eukaryotic,research and development of new ATFs agents have been difficult due to the limited numberof selective targets, also leading to toxicity. Silver nanoparticles (AgNPs)were considered, in recent years, particularly attractive for the production ofa new class of antimicrobials and the use of microorganisms for the synthesisof nanoparticles is relatively new in basic research and technology areas, openingup a completely new way to combat a wide range of pathogens. Although thehighly antibacterial effect of AgNPs has been described, their mechanism ofaction is yet to be fully elucidated. This study firstly evaluated the activity of biosynthesized AgNPs in Candida albicans planktoniccells and then the effect over biofilms.TheAgNPs was synthesized by the supernatant of Pseudomonasaeruginosa and characterized by Ultraviolet-visible (UV-vis)spectroscopy, dynamic light scattering (DLS) and transmission electronmicroscopy (TEM), previously by Quinteroset al, 2016.Minimum inhibitory (MIC), minimum fungicidal concentrations for planktoniccells (MFC) and minimum biofilm inhibitory concentration (MBIC) ofthe AgNPs and amphotericin B (AmB)against C. albicans were determined byplate microdilution technique at sub y supra CIM concentration. Biofilmformation (48 h of incubation) was assayed by adhesion to 96-well plate andcrystal violet (CV) stain (0.1 OD595nm=1BBU). Viable cells were determined by enumerationcolony-forming units per milliliter (CFU/mL) and the results showed a good correlation with the CV assay.  Ourresults demonstrate that AgNPs are potentinhibitors of C. albicans planktonic cells. The MIC results showedthat AgNPs were fungicidal against C.albinans SC5314 (0.037 pM) and C. albinans L20 (0.15 pM) at very lowconcentrations compared to silver standard (AgNO3 4 x 107 pMand 2 x 107 pM respectively) and AmB (2.7 x 105 pM). Biofilmreduction of both strains was obtained, however, sessile cells are not fullyremoved.These results are promising for its future application,due to the high activity observed at low concentrations. The biosynthesized AgNPs solution is a promising ATFs agents, these approachesare expected to be helpful in finding newmolecules to helpresistance to ATFs. Nanoparticles are now considered a viablealternative and seem to have a high potential to solve the problem of theemergence of bacterial multidrug resistance.