Insights into the Multi-Azole Resistance Profile in Candida haemulonii Species Complex

Laura Nunes Silva,Eamim Daidrê Squizani,Simone Santiago Carvalho Oliveira,Lívia Kmetzsch,Lucas Barros Magalhães,Marta Helena Branquinha,Lívia De Souza Ramos,André Luis Souza Dos Santos,Marilene Henning Vainstein

doi:10.3390/jof6040215

Abstract

The Candida haemulonii complex (C. duobushaemulonii, C. haemulonii, and C. haemulonii var. vulnera) is composed of emerging, opportunistic human fungal pathogens able to cause invasive infections with high rates of clinical treatment failure. This fungal complex typically demonstrates resistance to first-line antifungals, including fluconazole. In the present work, we have investigated the azole resistance mechanisms expressed in Brazilian clinical isolates forming the C. haemulonii complex. Initially, 12 isolates were subjected to an antifungal susceptibility test, and azole cross-resistance was detected in almost all isolates (91.7%). In order to understand the azole resistance mechanistic basis, the efflux pump activity was assessed by rhodamine-6G. The C. haemulonii complex exhibited a significantly higher rhodamine-6G efflux than the other non-albicans Candida species tested (C. tropicalis, C. krusei, and C. lusitaneae). Notably, the efflux pump inhibitors (Phe-Arg and FK506) reversed the fluconazole and voricolazole resistance phenotypes in the C. haemulonii species complex. Expression analysis indicated that the efflux pump (ChCDR1, ChCDR2, and ChMDR1) and ERG11 genes were not modulated by either fluconazole or voriconazole treatments. Further, ERG11 gene sequencing revealed several mutations, some of which culminated in amino acid polymorphisms, as previously reported in azole-resistant Candida spp. Collectively, these data point out the relevance of drug efflux pumps in mediating azole resistance in the C. haemulonii complex, and mutations in ERG11p may contribute to this resistance profile.

Highlights

The recently described Candida haemulonii clade has caused deep concerns in hospital environments worldwide, since its members are able to cause life-threatening infections presenting high rates of clinical treatment failures [1]
The MIC values determined for 12 clinical isolates forming the C. haemulonii species complex (C. haemulonii, n = 5 isolates; C. duobushaemulonii, n = 4; and C. haemulonii var. vulnera, n = 3) against five different azoles (FLC, ITC, KTC, PSC, and VRC) were summarized in Table 2 and Table S1
Despite some isolates remaining susceptible to VRC, the MIC distribution exhibited a peak at 16 mg/L, with 66% (n = 8) of isolates being resistant to this azole

Summary

Introduction

The recently described Candida haemulonii clade has caused deep concerns in hospital environments worldwide, since its members are able to cause life-threatening infections presenting high rates of clinical treatment failures [1]. The C. haemulonii clade is composed of emerging, opportunistic, J. J. Fungi 2020, 6, 215 and multidrug-resistant species formed by C. auris, C. duobushaemulonii, C. haemulonii sensu stricto, C. haemulonii var. Vulnera, C. pseudohaemulonii, and C. vulturna [1,2]. Vulnera, which form the C. haemulonii complex, have been identified in different geographic regions in the globe, prominently in Latin. American (e.g., Brazil) and Asian (e.g., India and China) countries.

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Discussion

Conclusion