Overexpression of Both ERG11 and ABC2 Genes Might Be Responsible for Itraconazole Resistance in Clinical Isolates of Candida krusei

Abstract

ObjectiveTo study the main molecular mechanisms responsible for itraconazole resistance in clinical isolates of Candida krusei.MethodsThe 14α-demethylases encoded by ERG11 gene in the 16 C.krusei clinical isolates were amplified by polymerase chain reaction (PCR), and their nucleotide sequences were determined to detect point mutations. Meanwhile, ERG11 and efflux transporters (ABC1 and ABC2) genes were determined by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) for their expression in itraconazole-resistant (R), itraconazole-susceptible dose dependent (SDD) and itraconazole-susceptible (S) C.krusei at the mRNA level.ResultsWe found 7-point mutations in ERG11 gene of all the C.krusei clinical isolates, including 6 synonymous mutations and 1 missense mutation (C44T). However, the missense mutation was found in the three groups. The mRNA levels of ERG11 gene in itraconazole-resistant isolates showed higher expression compared with itraconazole-susceptible dose dependent and itraconazole-susceptible ones (P = 0.015 and P = 0.002 respectively). ABC2 gene mRNA levels in itraconazole-resistant group was significantly higher than the other two groups, and the levels of their expression in the isolates appeared to increase with the decrease of susceptibility to itraconazole (P = 0.007 in SDD compared with S, P = 0.016 in SDD with R, and P<0.001 in S with R respectively). While ABC1 gene presented lower expression in itraconazole resistant strains. However, the mRNA levels of ERG11, ABC1 and ABC2 in a C.krusei (CK10) resistant to both itraconazole and voriconazole were expressed highest in all the itraconazole-resistant isolates.ConclusionsThere are ERG11 gene polymorphisms in clinical isolates of C.krusei. ERG11 gene mutations may not be involved in the development of itraconazole resistance in C.krusei. ERG11 and ABC2 overexpression might be responsible for the acquired itraconazole resistance of these clinical isolates.

Population genomics shows no distinction between pathogenic Candida krusei and environmental Pichia kudriavzevii: One species, four names

“…Two strains from a hospital in Ireland form the closest pair in the tree (C-IE2, C-IE4) and group weakly with a third (C-IE1), but three other strains from the same hospital are scattered across the tree. All four clinical isolates from Tianjin, China [ 57 ] lie in Clade 2, and among these, two strains form a close pair (C-CN3, C-CN4) and are both triploid. The only sample from soil in our dataset, E-JP4, groups with samples from faeces (C-BR1) and sewage (E-JP1) to form Clade 1, indicating possible clustering by habitat.…”

Novel point mutations in the ERG11 gene in clinical isolates of azole resistant Candida species

“… He et al (2015) studied the molecular mechanisms responsible for itraconazole resistance in clinical isolates of C. krusei and found ERG11 gene polymorphisms that may not be involved in the development of itraconazole resistance in C. krusei , but overexpression of ERG11 and ABC2 might be responsible for the acquired itraconazole resistance of the clinical isolates.…”

Azole Antifungal Resistance in Candida albicans and Emerging Non-albicans Candida Species

“…For example, analysis of itraconazole-resistant C. krusei isolates revealed that reduced intracellular content of the drug and not altered affinity for the drug target likely drives itraconazole resistance (Marichal et al, 1995; Venkateswarlu et al, 1996). However, more recently it has been suggested that overexpression of genes encoding both Erg11p and the efflux pump Abc2p may also play a role with itraconazole resistance (Tavakoli et al, 2010; He et al, 2015). Despite its fungicidal activity in C. krusei (Rubio et al, 2005), resistance to voriconazole has also emerged, and current research supports a theory where overexpression of the genes encoding the efflux pump Abc2 and Erg11 impart more transient resistance properties, while increased expression of Abc1p and point mutations in ERG11 predominate as time progresses to yield a stably resistant pathogen in the prolonged presence of voriconazole (Ricardo et al, 2014).…”