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Objectives: Fungal infections in immunocompromised patients have been contributing to the increasing morbidity and mortality ofthese patients, especially associated to yeast resistance to antifungal therapy. The increase in antibiotic-resistant microorganisms has prompted interest in the use of silver as an antimicrobial agent. Thus, the aim of this study was to evaluate the antifungal efficacy of silver nanoparticles against Candida a/bicans and Candida glabrata biotilms.

Methods: Spherical nano-silver (average diameter snm) particles were synthesized by silver nitrate reduction with sodium citrate. Minimal inhibitory concentration (MIC) tests were performed for C. a/bicans (n= 2) and C. glabrata (n= 2) grown in suspension using the micro broth dilution method. Silver nanoparticles were applied on adhered cells (2 h) or biotilms (48 h) and after 24h biotilms were characterized by colony forming units (CFUs) enumeration and total biomass quantification (using crystal violet staining). Results: Interestingly, C. glabrata MIC values were higher (0.4-3· 3 j. Jg/ml) than C. albicans (0.4-1.6 jJg/mL). Furthermore, the results obtained revealed that silver nanoparticles were more effective in reducing 24h biotilms' biomass when applied onto adhered cells (2h) than on pre-formed biofilms (48h), with the exception of C. glabrata clinical isolate, which in both cases had a reduction around 90%. Regarding cell viability, silver nanoparticles were highly effective on adhered C. glabrata (reduction of around 70%) and respective biotilms (reduction of around so%). On C. a/bicans the effect was not so notorious but there was also a reduction on the number of biotilm …