Notable Trend of Increase in Azole Non-Susceptible Candida tropicalis Causing Invasive Candidiasis in China, August 2009 to July 2014

X. Fan, M. Xiao, H. Wang, Y-C. Xu

Author address: 

Peking Union Med. Coll. Hosp., Beijing, China

Abstract: 

Background: Worldwide, C. tropicalis has become the first to fourth leading cause of invasive candidiasis (IC). Here we report a notable and continuous increase in azole non-susceptibility among C. tropicalis causing IC in China in the past half-decade.Methods: Between August 2009 and July 2014, 585 C. tropicalis isolates were collected from 10 hospitals from the China Hospital Invasive Fungal Surveillance Net (CHIF-NET) study. The in vitro susceptibility of isolates to nine antifungal drugs - fluconazole, voriconazole, itraconazole, posaconazole, caspofungin, micafungin, anidulafungin, amphotericin B and 5-flucytosine - was determined by Sensititre YeastOne YO10 methodology. Current available species-specific clinical breakpoint or epidemiological cut-off values were used for interpretation of results.Results: Overall, 22.1% and 19.5% of isolates were non-susceptible to fluconazole and voriconazole, respectively, with 10.4% of the isolates showing cross-resistance to both. Over five years, there was a significant decrease in azole susceptibilities, particularly during the last two years. As shown in the Figure, the non-susceptible rate of C. tropicalis isolates to fluconazole and voriconazole continuously increased from 10.4% to 42.6% for fluconazole, and from 10.4% to 39.1% for voriconazole. The prevalence of fluconazole-voriconazole cross-resistant isolates also increased from 6.6% to 21.7%. Moreover, although all isolates remained of wild-type phenotype to itraconazole and posaconazole, the GM MIC and MIC50 values for these two drugs also rose by over two fold, and the MIC90 values had a 4-fold increase in the study period. In comparison, all C. tropicalis isolates included in the present study were of wild-type to amphotericin B, and only 0.7% of isolates were of non-wild type phenotype to 5-flucytosine. Over 99% of the isolates remained susceptible to all three echinocandin agents tested. In addition, during the five years of surveillance, there were no significant changes (within ±1 dilution) in MIC50, MIC90, and GM MIC values for these drugs.Conclusions: Our findings show an unusual high-level of fluconazole and voriconazole resistance, and a significant trend of decreasing azole susceptibility. Further study is needed to identify the contributing factors.
2016

abstract No: 

SATURDAY-296

Full conference title: 

ASM Microbe 2016
    • ASM microbe 1st (2016)