Expression Pattern of Drug-Resistance Genes in Matched Clinical Isolates of Candida albicans at Variable Fluconazole Exposure Times

Candida albicans is an opportunistic fungus that exists naturally in the vaginal, urinary, and gastrointestinal tracts of humans. Typically, this yeast remains balanced with the body’s other natural microbial flora and the host immune system. However, infections may occur in individuals with compromised immune systems. A common drug used to treat these infections is fluconazole (FLC), a fungistatic azole targeting lanosterol 14α-demethylase (Erg11) in the ergosterol biosynthesis pathway. In some clinical isolates, resistance to FLC is due to overexpression of a) the encoding genes CDR1 and CDR2 for the ABC Transporters, b) the Major Facilitator Transporter encoding gene MDR1, or c) ERG11, the azole target gene. Previous studies have shown gene expression in a matched set of clinical isolates is maximized at the drug concentration that matches the minimum inhibitory concentration (MIC80) of the strain to FLC. This study investigates the gene expression levels of the drug resistant genes in selected C. albicans isolates from the matched series in the presence of their corresponding MIC80 to FLC at different times in the growth cycle. The four isolates used in this study were selected from a series of 17 isolates all taken from the same patient. Quantitative real time PCR (qRT-PCR) was used to measure mRNA expression of the aforementioned genes in the presence and absence of FLC at their respective MIC80 concentrations at growth times ranging from 1 hour to 32 hours. Gene expression in the presence of drug was compared to the respective expression levels in the absence of drug. The results from the experiment demonstrate variable gene expression between susceptible and resistant isolates. FLC susceptible isolates began overexpressing CDR2, MDR1, and ERG11 at 4 hours of drug exposure. FLC exposure does not affect CDR1 expression in any of the four isolates with the exception of isolates 1 and 4 at 32 hours. As the target of FLC, ERG11 overexpression is induced by drug in all strains. Susceptible isolates begin overexpressing resistance genes earlier and at higher levels than resistant isolates that express high basal gene expression in the absence of drug. Therefore, gene overexpression of resistance genes in response to the exposure time of FLC at MIC80 concentrations varies depending on the resistant gene, and its basal expression levels in resistant isolates.

Name thesis:degree_name

M.S. (Master of Science)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Cellular and Molecular Biology (UMKC)

Grantor

University of Missouri--Kansas City

Year dc:date.issued

2016

Author dc:creator

• Geanes, Eric Stephen

Advisor dc:contributor.advisor

• White, Theodore C.

Handle dc:identifier.uri

https://hdl.handle.net/10355/94501

OAI identifier oai:identifier

oai:mospace.umsystem.edu:10355/94501