Selected mechanisms of molecular resistance of Candida albicans to azole drugs.

Karolina Gołąbek; Joanna Katarzyna Strzelczyk; Aleksander Owczarek; Piotr Cuber; Anna Ślemp-Migiel; Andrzej Wiczkowski

Karolina Gołąbek Department of Medical and Molecular Biology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia, Zabrze, Poland.;
Joanna Katarzyna Strzelczyk Department of Medical and Molecular Biology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia, Zabrze, Poland.;
Aleksander Owczarek Statistical Division, Department of Instrumental Analysis, School of Pharmacy with the Division of Laboratory Medicine in Sosnowiec, Medical University of Silesia, Sosnowiec, Poland.;
Piotr Cuber Department of Parasitology, School of Pharmacy with the Division of Laboratory Medicine in Sosnowiec, Medical University of Silesia, Sosnowiec, Poland.;
Anna Ślemp-Migiel Laboratory of Microbiology in Hospital in Nowy Targ, Nowy Targ, Poland.;
Andrzej Wiczkowski Department of Medical and Molecular Biology, School of Medicine with the Division of Dentistry in Zabrze, Medical University of Silesia, Zabrze, Poland.;

Abstract

A phenomenon of increasing resistance of Candida spp. to azoles has been observed for several years now. One of the mechanisms of lack of sensitivity to azoles is associated with CDR1, CDR2, MRD1 genes (their products are active transport pumps conditioning drug efflux from pathogen's cell), and ERG11 gene (encoding lanosterol 14α-demethylase). Test material was 120 strains of Candida albicans (60 resistant and 60 susceptible to azole drugs) obtained from clinical samples. The first stage of experiment assessed the expression of CDR1, CDR2, MDR1 and ERG11 genes by Q-PCR. The impact of ERG11 gene's mutations on the expression of this gene was analysed. The final stage of the experiment assessed the level of genome methylation of Candida albicans strains. An increase in the expression of CDR2, MDR1 and ERG11 was observed in azole-resistant strains of Candida albicans in comparison to strains sensitive to this class of drugs. Furthermore, 19 changes in the sequence of ERG11 were detected in tested strains. Four of the discovered mutations: T495A, A530C, G622A and A945C led to the following amino acid substitutions: D116E, K128T, V159I and E266D, respectively. It has also been found that statistically five mutations: T462C, G1309A, C216T, C1257T and A945C affected the expression of ERG11. The applied method of assessing the level of methylation of Candida albicans genome did not confirm its role in the development of resistance to azoles. The results indicate however, that resistance of Candida albicans strains to azole drugs is multifactorial.