In vitro susceptibility testing of Candida species isolated from blood stream infections to five conventional antifungal drugs

Abstract

Candida is an opportunistic fungal pathogen which can cause fatal bloodstream infections (BSIs) in immunocompromised and immunodeficient persons. In this study, the susceptibility of 196 Candida species isolated from bloodstream infections (BSI) to 5 antifungal drugs were conducted from October 2014 through October 2017. The antifungal drugs used in this study were including fluconazole, itraconazole, voriconazole, Amphotericin B and Caspofungin. From 196 studied isolates, Candida albicans comprised 63.3% of the isolates, followed by C.parapsilosis (18.9 %), C. glabrata (8.7%), C. tropicalis (6.1%), C.krusei (2%) and C.gillermundii (1%). In this study, all isolates of Candida albicans and Candida non-albicans species were completely resistant to voriconazole and itraconazole. Of the 196 Candida isolates, 80 isolates with MIC of 32-16 μg/ml had a dose dependent susceptibility to fluconazole and 111 isolates showed resistance (MIC=64 μg / ml) and only 5 isolates were sensitive (MIC=8 μg / ml) to fluconazole. In this study, out of 196 isolates, 37 isolates were sensitive to amphotericin (MIC=1 μg/ml) and 159 isolates were resistant to amphotericin B (MIC>1 μg/ml). Caspofungin was effective on 104 isolates (MIC<2 μg/ml) and 92 isolates were non-susceptible (MIC>2 μg / ml) to this drug. Out of 124 isolates of Candida albicans, 3 were susceptible, 61 susceptible dose dependent and 60 were resistant to fluconazole. Only 24 isolates were susceptible to amphotericin B and 100 isolates showed resistance to this antifungal drug. Eighty-eight isolates were sensitive to caspofungin and 36 isolates were insensitive. With respect to susceptibility to fluconazole, among 37 isolates of Candida parapsilosis, one was identified as susceptible, 13 isolates were susceptible dose dependent and 13 were resistant. Of these isolates, five were susceptible and 32 isolates were resistant to amphotericin B and caspofungin. Of 12 isolates of Candida tropicalis, 11 showed resistance and 1 was susceptible dose dependent to fluconazole. Of these isolates, 11 were resistant to amphotericin B and 1 isolate was sensitive. Ultimately, only 2 isolates showed susceptibility to caspofungin. Out of 17 isolates of Candida glabrata, 13 isolates were resistant, and 4 isolates had a dose-dependent sensitivity to fluconazole. Eight isolates were susceptible and 9 isolates were resistant to caspofungin. Seven isolates were susceptible and 10 isolates were resistant to amphotericin B. All four Candida krusei isolates showed resistance to the five drugs used in the study. Of the two Candida guilliermondii isolates, both were resistant to amphotericin B, but 1 was sensitive to fluconazole and 1 was identified to be dose-dependent susceptible. One isolate was resistant to and the other one was susceptible to caspofungin. Our findings shows the prevalence of resistant candida species to conventional treatments and indicate that candidemia caused by Candida resistant species is incrasing. Keywords: Candidiasis; Antifungal drugs; Candidemia; Iran