In Vitro Antifungal Susceptibility of Candidemia Agents and Detection of Their Biofilm Production by Two Different Methods

Candida bloodstream infections are a significant cause of morbidity and mortality in hospitalized patients. The most important contribution of biofilm is the higher antifungal resistance than planktonic cells. We aimed to investigate the biofilm formation rate and antifungal susceptibility characteristics of our bloodstream isolates, and evaluate two different biofilm detection methods. A total of 200 bloodstream Candida isolates were included. The biofilms were formed on 96-well microtiter plates and measured by spectrophotometric percent transmittance and 2,3-bis(2- methoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium- 5-carboxanilide colorimetric assay. In addition antifungal susceptibilities of these isolates were evaluated against caspofungin, anidulafungin and amphotericin B by reference method. Biofilm production rate was considerably high among our bloodstream isolates. The most important biofilm producer species was C. tropicalis; C. glabrata had the lowest biofilm production rate. The consistency rate between biofilm detection methods was 66%. Remarkable antifungal resistance was not observed among our isolates in general. In conclusion, biofilm production in Candida species is an important virulence factor, and its rate is considerably high in bloodstream isolates. At present, a standardized method has not been established to detect the biofilm formation.