Two Sequential Clinical Isolates of Candida glabrata with Multidrug-Resistance to Posaconazole and Echinocandins.

Qiqi Wang,Yun Li,Ence Yang,Tianyu Liang,Bo Zheng,Wei Liu,Xuan Cai,Xinyu Yang,Zhe Wan,Ruoyu Li

doi:10.3390/antibiotics10101217

Abstract

Candida glabrata is one of the most prevalent causative pathogens of invasive candidiasis, and multidrug-resistant strains are emerging. We identified two clinical isolates of C. glabrata, BMU10720 and BMU10722 sequentially isolated from one patient with multidrug-resistance to posaconazole (POS), caspofungin (CAS), micafungin (MCF), and anidulafungin (ANF). Overexpression of ERG11 in BMU10720 and CDR1 in BMU10722 were detected at basal level. When exposed to POS, CDR1 was significantly up-regulated in both isolates compared with susceptible reference strain, while ERG11 was up-regulated considerably only in BMU10720. PDR1 sequencing revealed that both isolates harbored P76S, P143T, and D243N substitutions, while ERG11 was intact. Cdr1 inhibitor FK520 reversed POS-resistance by down-regulating ERG11 expression. FKS sequencing revealed that both isolates harbored S663P substitution in FKS2, and four single nucleotide polymorphisms (SNPs) existed in FKS2 genes between BMU10720 and BMU10722, while FKS1 was intact. Both FKS1 and FKS2 were up-regulated by CAS in BMU10720 and BMU10722. FK520 down-regulated FKS2 expression induced by CAS through inhibiting calcineurin, resulting in synergic effect with echinocandins as well as Congo Red and Calcofluor White, two cell wall-perturbing agents. In conclusion, the multidrug-resistance of C. glabrata isolates in our study was conferred by different mechanisms. CDR1 and ERG11 overexpression in one isolate and only CDR1 overexpression in the other isolate may mediate POS-resistance. S663P mutation in FKS2 and up-regulation of FKS2 may contribute to echinocandin-resistance in both isolates.

Highlights

Candida albicans remains the most prevalent Candida species causing Invasive candidiasis (IC), the past decades have witnessed an epidemiological shift to non-albicans spp., among which Candida glabrata is one of the most common pathogens and exhibits an increasing trend [1,2,3]
The MICs of POS against BMU10720 and BMU10722 were 4 mg/L (Table 2), which were defined as NWT to POS (ECV is 1 mg/L) [22]
Overexpression of ERG11 plays a subtle role in triazole-resistance in C. glabrata, another study showed that ERG11 up-regulation was inducible in susceptible C. albicans growing in subinhibitory concentrations of FLC [33]

Summary

Introduction

Candida albicans remains the most prevalent Candida species causing IC, the past decades have witnessed an epidemiological shift to non-albicans spp., among which Candida glabrata is one of the most common pathogens and exhibits an increasing trend [1,2,3]. C. glabrata has become the most prevalent non-albicans Candida spp. for candidemia in the United States and the third most common in China [4,5]. Triazoles, such as fluconazole (FLC), itraconazole (ITC), voriconazole (VRC), and posaconazole (POS), acting by binding and inhibiting the

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