Characterization of Candida glabrata complex isolates in blood cultures and evaluation of sensitivity to antifungal

Abstract

Candida glabrata has assumed great importance in clinical medicine, since acquired resistance   to fluconazole had been described. Furthermore, studies have shown the weak in vitro activity   of other azole drugs against isolates of this species. Since C. glabrata is an agent of invasive   infections, monitoring the effectiveness of antifungal agents used in medical practice against   isolates of this species has become of great importance. C. bracarensis and C. nivariensis   are phenotypically related species to C. glabrata and so it is necessary molecular methods to   identify properly these members. In Latin America, the occurrence of bloodstream infections   in C. glabrata and related species is not as high as in North America, and little is known about   their distribution and antifungal susceptibility profile in this region. In this study, we analyzed   75 isolates with morphological and biochemical features of C. glabrata obtained from the   bloodstream of patients treated in hospitals in the state of São Paulo, between 2007-2013. The   minimum inhibitory concentrations (MIC) of five antifungal drugs, namely: amphotericin B,   caspofungin, voriconazole, fluconazole and itraconazole were determined by microdilution   reference method M27-A3 from the Clinical and Laboratory Standards Institute (CLSI).   The fungicidal action of amphotericin B was evaluated by the method of time-kill curves.   The investigation of the two related species was performed with polymerase chain reaction   (PCR) in all isolates. No isolate of C. bracarensis and C. nivariensis was found in this study.   Resistance to itraconazole was found in 18.6% (14) strains of C. glabrata. High MIC values   of voriconazole (> 0.5 mg/L), according to epidemiological cut-off were observed for two   strains. The fluconzole-MICs ranged from 4mg/L to 16mg/L, caspofungin-MIC were between   0.03 mg/L and 0.5 mg/L, and amphotericin B-MIC were between 0.12 mg/L and 1 mg/L. Timekill   curves method showed that the majority of strains died before 24 h, remaining viable 3   isolates, and 2 of them suffered no fungicidal action of amphotericin B under the experimental   conditions. It was concluded that fluconazole, amphotericin B, and caspofungin showed   strong inhibitoy effect against all 75 clinical isolates of C. glabrata, however, resistance to   itraconazole and lower susceptibility to voriconazole, besides tolerance to killing effect of   amphotericin B was observed. These data indicate the emergence of strains resistant to more   than one drug and reinforce the need to monitor the activity of antifungal agents used in   clinical medicine, in order to optimize the treatment of cases of candidemia.