Low level of antifungal resistance of Candida glabrata blood isolates in Turkey: Fluconazole minimum inhibitory concentration and FKS mutations can predict therapeutic failure

Abstract

Background Candida glabrata is the third leading cause of candidaemia in Turkey; however, the data regarding antifungal resistance mechanisms and genotypic diversity in association with their clinical implication are limited. Objectives To assess genotypic diversity, antifungal susceptibility and mechanisms of drug resistance of C glabrata blood isolates and their association with patients' outcome in a retrospective multicentre study. Patients/Methods Isolates from 107 patients were identified by ITS sequencing and analysed by multilocus microsatellite typing, antifungal susceptibility testing, and sequencing of PDR1 and FKS1/2 hotspots (HSs). Results Candida glabrata prevalence in Ege University Hospital was twofold higher in 2014‐2019 than in 2005‐2014. Six of the analysed isolates had fluconazole MICs ≥ 32 µg/mL; of them, five harboured unique PDR1 mutations. Although echinocandin resistance was not detected, three isolates had mutations in HS1‐Fks1 (S629T, n = 1) and HS1‐Fks2 (S663P, n = 2); one of the latter was also fluconazole‐resistant. All patients infected with isolates carrying HS‐FKS mutations and/or demonstrating fluconazole MIC ≥ 32 µg/mL (except one without clinical data) showed therapeutic failure (TF) with echinocandin and fluconazole; seven such isolates were collected in Ege (n = 4) and Gulhane (n = 3) hospitals and six detected recently. Among 34 identified genotypes, none were associated with mortality or enriched for fluconazole‐resistant isolates. Conclusion Antifungal susceptibility testing should be supplemented with HS‐FKS sequencing to predict TF for echinocandins, whereas fluconazole MIC ≥ 32 µg/mL may predict TF. Recent emergence of C glabrata isolates associated with antifungal TF warrants future comprehensive prospective studies in Turkey.

Recent Increase in the Prevalence of Fluconazole-Non-susceptible Candida tropicalis Blood Isolates in Turkey: Clinical Implication of Azole-Non-susceptible and Fluconazole Tolerant Phenotypes and Genotyping

“…We also revealed correlation between the genotype cluster and patient mortality, which has been previously shown for C. glabrata ( Byun et al, 2018 ; Arastehfar et al, 2019a ). The mortality rate observed in this study is similar to those reported for C. tropicalis in Iran ( Arastehfar et al, 2020a ), Italy ( Montagna et al, 2013 ), and the United States ( Andes et al, 2016 ), and to that observed for C. glabrata in Turkey ( Arastehfar et al, 2020e ). Collectively, these findings emphasize the importance of using genotyping techniques in clinical settings, which may provide insightful observations with predictive prognostic values.…”

“…In contrast to a previous study reporting the absence of azole-resistant C. tropicalis ( Arikan-Akdagli et al, 2019 ), however, we identified 18.6% ANS C. tropicalis isolates, among which 93 and 58% were cross-resistant to three azoles or fluconazole + voriconazole, respectively. Importantly, we observed an alarming rate (40–50%) of ANS isolates in some hospitals in 2019, which is also documented in other studies ( Arendrup et al, 2011 ; Chen et al, 2019 ; Pfaller et al, 2019 ); these statistics require particular attention, especially in the countries where azoles are the main antifungals used for candidemia therapy ( Sellami et al, 2011 ; Singh et al, 2018 ; Arastehfar et al, 2019a , 2020e ). Notable variations in the rate of azole-resistant isolates (0–100%) observed among the analyzed hospitals could be attributed to differences in intervention strategies, including the use of azoles and infection control practices.…”

“…A recent study explored antifungal susceptibility patterns of Candida bloodstream isolates in Turkey (1997–2017) and reported the lack of drug resistance for C. tropicalis ( Arikan-Akdagli et al, 2019 ). However, our single- and multi-center investigations conducted later in Turkey have revealed a very recent (from 2017 onward) emergence of azole/echinocandin-resistant and even MDR Candida species ( Arastehfar et al, 2020b,c , e ), suggesting the existence of the same trend for C. tropicalis . Therefore, we conducted a comprehensive multi-center study to update the rate of antifungal resistance among C. tropicalis blood isolates recovered in 2017–2019 in Turkey; some isolates recovered before 2017 but not analyzed in the previous study ( Arikan-Akdagli et al, 2019 ) were also included.…”

“…Isolates were grown on Sabouraud glucose agar (SGA, Merck, Darmstadt, Germany) and chromogenic media (Candiselect, Bio-Rad, Hercules, CA, United States) at 35°C for 24–48 h. DNA was isolated by a CTAB method ( Arastehfar et al, 2018 ) and species identification was performed by sequencing internal transcribed spacers ITS1 and ITS4 ( Stielow et al, 2015 ). Therapeutic failure was considered if fever persisted and blood culture remained positive ( Arastehfar et al, 2020e ) despite antifungal treatment and the mortality rate reported herein was all-cause.…”

The Quiet and Underappreciated Rise of Drug-Resistant Invasive Fungal Pathogens

“…Therefore, isolates displaying echinocandin resistance without known mutations in the HS regions may harbor non-synonymous mutations located anywhere in the FKS genes. Importantly, it has been documented that occasionally C. glabrata blood isolates carrying mutation in HS1-Fks1 (S629T) are fully susceptible to echinocandins, while the patient infected with such isolate showed therapeutic failure [107]. Therefore, combination of both antifungal susceptibility testing (AFST) and FKS sequencing can more precisely predict therapeutic failure when treating candidemia patients with echinocandins.…”