scholarly journals Multiple Molecular Mechanisms Contribute to a Stepwise Development of Fluconazole Resistance in Clinical Candida albicans Strains

1998 ◽  
Vol 42 (12) ◽  
pp. 3065-3072 ◽  
Author(s):  
Renate Franz ◽  
Steven L. Kelly ◽  
David C. Lamb ◽  
Diane E. Kelly ◽  
Markus Ruhnke ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Candida Albicans ◽  
Molecular Mechanisms ◽  
Multiple Drug Resistance ◽  
Genetic Alterations ◽  
Mutant Form ◽  
Mrna Levels ◽  
Fluconazole Resistance ◽  
Stepwise Development ◽  
Target Enzyme

ABSTRACT From each of two AIDS patients with oropharyngeal candidiasis, fiveCandida albicans isolates from recurrent episodes of infection which became gradually resistant against fluconazole during antimycotic treatment were analyzed for molecular changes responsible for drug resistance. In both patients, a single C. albicans strain was responsible for the recurrent infections, but the CARE-2 fingerprint pattern of the isolates exhibited minor genetic alterations, indicating that microevolution of the strains took place during fluconazole therapy. In the isolates from patient 1, enhanced mRNA levels of theMDR1 gene, encoding a multiple drug resistance protein from the superfamily of major facilitators, and constitutive high expression of the ERG11 gene, coding for the drug target enzyme sterol 14α-demethylase, correlated with a stepwise development of fluconazole resistance. The resistant strains exhibited reduced accumulation of fluconazole and, for the last in the series, a slight increase in drug needed to inhibit sterol 14α-demethylation in vitro. In the isolates from patient 2, increasedMDR1 mRNA levels and the change from heterozygosity to homozygosity for a mutant form of the ERG11 gene correlated with continuously decreased drug susceptibility. In this series, reduced drug accumulation and increased resistance in the target enzyme activity, sterol 14α-demethylase, were observed. These results demonstrate that different molecular mechanisms contribute to a gradual development of fluconazole resistance in C. albicans.

scholarly journals Increased mRNA levels of ERG16, CDR, and MDR1 correlate with increases in azole resistance in Candida albicans isolates from a patient infected with human immunodeficiency virus.

1997 ◽  
Vol 41 (7) ◽  
pp. 1482-1487 ◽  
Author(s):  
T C White
Keyword(s):  
Human Immunodeficiency Virus ◽  
Candida Albicans ◽  
Abc Transporter ◽  
Genetic Alterations ◽  
Antifungal Drugs ◽  
Cross Resistance ◽  
Mrna Levels ◽  
Fluconazole Resistance ◽  
Immunodeficiency Virus ◽  
Major Facilitator

Resistance to antifungal drugs, specifically azoles such as fluconazole, in the opportunistic yeast Candida albicans has become an increasing problem in human immunodeficiency virus (HIV)-infected individuals. The molecular mechanisms responsible for this resistance have only recently become apparent and can include alterations in the target enzyme of the azole drugs (lanosterol 14alpha demethylase [14DM]), or in various efflux pumps from both the ABC transporter and major facilitator gene families. To determine which of these possible mechanisms was associated with the development of drug resistance in a particular case, mRNA levels have been studied in a series of 17 clinical isolates taken from a single HIV-infected patient over 2 years, during which time the levels of fluconazole resistance of the strain increased over 200-fold. Using Northern blot analysis of steady-state levels of total RNA from these isolates, we observed increased mRNA levels of ERG16 (the 14DM-encoding gene), CDR1 (an ABC transporter), and MDR1 (a major facilitator) in this series. The timing of the increase in mRNA levels of each of these genes correlated with increases in fluconazole resistance of the isolates. Increased mRNA levels were not observed for three other ABC transporters, two other genes in the ergosterol biosynthetic pathway, or the NADPH-cytochrome P-450 oxidoreductase gene that transfers electrons from NADPH to 14DM. Increases in mRNA levels of ERG16 and CDR1 correlated with increased cross-resistance to ketoconazole and itraconazole but not to amphotericin B. A compilation of the genetic alterations identified in this series suggests that resistance develops gradually and is the sum of several different changes, all of which contribute to the final resistant phenotype.

scholarly journals Prevalence of Molecular Mechanisms of Resistance to Azole Antifungal Agents in Candida albicans Strains Displaying High-Level Fluconazole Resistance Isolated from Human Immunodeficiency Virus-Infected Patients

2001 ◽  
Vol 45 (10) ◽  
pp. 2676-2684 ◽  
Author(s):  
Sofia Perea ◽  
José L. López-Ribot ◽  
William R. Kirkpatrick ◽  
Robert K. McAtee ◽  
Rebecca A. Santillán ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Candida Albicans ◽  
Molecular Mechanisms ◽  
Azole Resistance ◽  
Mechanisms Of Resistance ◽  
Fluconazole Resistance ◽  
Immunodeficiency Virus ◽  
Genes Encoding ◽  
High Level ◽  
Target Enzyme

ABSTRACT Molecular mechanisms of azole resistance in Candida albicans, including alterations in the target enzyme and increased efflux of drug, have been described, but the epidemiology of the resistance mechanisms has not been established. We have investigated the molecular mechanisms of resistance to azoles inC. albicans strains displaying high-level fluconazole resistance (MICs, ≥64 μg/ml) isolated from human immunodeficiency virus (HIV)-infected patients with oropharyngeal candidiasis. The levels of expression of genes encoding lanosterol 14α-demethylase (ERG11) and efflux transporters (MDR1 and CDR) implicated in azole resistance were monitored in matched sets of susceptible and resistant isolates. In addition,ERG11 genes were amplified by PCR, and their nucleotide sequences were determined in order to detect point mutations with a possible effect in the affinity for azoles. The analysis confirmed the multifactorial nature of azole resistance and the prevalence of these mechanisms of resistance in C. albicans clinical isolates exhibiting frank fluconazole resistance, with a predominance of overexpression of genes encoding efflux pumps, detected in 85% of all resistant isolates, being found. Alterations in the target enzyme, including functional amino acid substitutions and overexpression of the gene that encodes the enzyme, were detected in 65 and 35% of the isolates, respectively. Overall, multiple mechanisms of resistance were combined in 75% of the isolates displaying high-level fluconazole resistance. These results may help in the development of new strategies to overcome the problem of resistance as well as new treatments for this condition.

scholarly journals Evolution of Drug Resistance in Experimental Populations of Candida albicans

2000 ◽  
Vol 182 (6) ◽  
pp. 1515-1522 ◽  
Author(s):  
Leah E. Cowen ◽  
Dominique Sanglard ◽  
David Calabrese ◽  
Caroline Sirjusingh ◽  
James B. Anderson ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Candida Albicans ◽  
Marker Genes ◽  
Gene Encoding ◽  
Fluconazole Resistance ◽  
Genomic Changes ◽  
Atp Binding Cassette Transporter ◽  
Experimental Populations ◽  
Major Facilitator ◽  
Different Levels

ABSTRACT Adaptation to inhibitory concentrations of the antifungal agent fluconazole was monitored in replicated experimental populations founded from a single, drug-sensitive cell of the yeast Candida albicans and reared over 330 generations. The concentration of fluconazole was maintained at twice the MIC in six populations; no fluconazole was added to another six populations. All six replicate populations grown with fluconazole adapted to the presence of drug as indicated by an increase in MIC; none of the six populations grown without fluconazole showed any change in MIC. In all populations evolved with drug, increased fluconazole resistance was accompanied by increased resistance to ketoconazole and itraconazole; these populations contained ergosterol in their cell membranes and were amphotericin sensitive. The increase in fluconazole MIC in the six populations evolved with drug followed different trajectories, and these populations achieved different levels of resistance, with distinct overexpression patterns of four genes involved in azole resistance: the ATP-binding cassette transporter genes,CDR1 and CDR2; the gene encoding the target enzyme of the azoles in the ergosterol biosynthetic pathway,ERG11; and the major facilitator gene, MDR1. Selective sweeps in these populations were accompanied by additional genomic changes with no known relationship to drug resistance: loss of heterozygosity in two of the five marker genes assayed and alterations in DNA fingerprints and electrophoretic karyotypes. These results show that chance, in the form of mutations that confer an adaptive advantage, is a determinant in the evolution of azole drug resistance in experimental populations of C. albicans.

scholarly journals Exploiting evolutionary trade-offs for posttreatment management of drug-resistant populations

2020 ◽  
Vol 117 (30) ◽  
pp. 17924-17931
Author(s):  
Sergey V. Melnikov ◽  
David L. Stevens ◽  
Xian Fu ◽  
Hui Si Kwok ◽  
Jin-Tao Zhang ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Molecular Mechanisms ◽  
Genetic Alterations ◽  
Trna Synthetase ◽  
Molecular Defect ◽  
Antibiotic Resistant ◽  
Resistance Evolution ◽  
Growth Defects ◽  
Trade Offs ◽  
Resistant Cells

Antibiotic resistance frequently evolves through fitness trade-offs in which the genetic alterations that confer resistance to a drug can also cause growth defects in resistant cells. Here, through experimental evolution in a microfluidics-based turbidostat, we demonstrate that antibiotic-resistant cells can be efficiently inhibited by amplifying the fitness costs associated with drug-resistance evolution. Using tavaborole-resistantEscherichia colias a model, we show that genetic mutations in leucyl-tRNA synthetase (that underlie tavaborole resistance) make resistant cells intolerant to norvaline, a chemical analog of leucine that is mistakenly used by tavaborole-resistant cells for protein synthesis. We then show that tavaborole-sensitive cells quickly outcompete tavaborole-resistant cells in the presence of norvaline due to the amplified cost of the molecular defect of tavaborole resistance. This finding illustrates that understanding molecular mechanisms of drug resistance allows us to effectively amplify even small evolutionary vulnerabilities of resistant cells to potentially enhance or enable adaptive therapies by accelerating posttreatment competition between resistant and susceptible cells.

scholarly journals Effects of Azole Antifungal Drugs on the Transition from Yeast Cells to Hyphae in Susceptible and Resistant Isolates of the Pathogenic Yeast Candida albicans

1999 ◽  
Vol 43 (4) ◽  
pp. 763-768 ◽  
Author(s):  
Kien C. Ha ◽  
Theodore C. White
Keyword(s):  
Drug Resistance ◽  
Candida Albicans ◽  
Molecular Mechanisms ◽  
Opportunistic Infections ◽  
Antifungal Drugs ◽  
Yeast Cells ◽  
Pathogenic Yeast ◽  
Oral Infections ◽  
Antifungal Drug Resistance ◽  
Hyphal Formation

ABSTRACT Oral infections caused by the yeast Candida albicansare some of the most frequent and earliest opportunistic infections in human immunodeficiency virus-infected patients. The widespread use of azole antifungal drugs has led to the development of drug resistance, creating a major problem in the treatment of yeast infections in AIDS patients and other immunocompromised individuals. Several molecular mechanisms that contribute to drug resistance have been identified. InC. albicans, the ability to morphologically switch from yeast cells (blastospores) to filamentous forms (hyphae) is an important virulence factor which contributes to the dissemination ofCandida in host tissues and which promotes infection and invasion. A positive correlation between the level of antifungal drug resistance and the ability to form hyphae in the presence of azole drugs has been identified. Under hypha-inducing conditions in the presence of an azole drug, resistant clinical isolates form hyphae, while susceptible yeast isolates do not. This correlation is observed in a random sample from a population of susceptible and resistant isolates and is independent of the mechanisms of resistance.35S-methionine incorporation suggests that growth inhibition is not sufficient to explain the inhibition of hyphal formation, but it may contribute to this inhibition.

scholarly journals Hospital Specificity, Region Specificity, and Fluconazole Resistance of Candida albicans Bloodstream Isolates

1998 ◽  
Vol 36 (6) ◽  
pp. 1518-1529 ◽  
Author(s):  
M. A. Pfaller ◽  
S. R. Lockhart ◽  
C. Pujol ◽  
J. A. Swails-Wenger ◽  
S. A. Messer ◽  
...  
Keyword(s):  
United States ◽  
Drug Resistance ◽  
Candida Albicans ◽  
Genetic Relatedness ◽  
Computer Assisted ◽  
Specific Probe ◽  
Fluconazole Resistance ◽  
Fluconazole Resistant ◽  
Species Specific ◽  
Close Genetic Relationship

In a survey of bloodstream infection (BSI) isolates across the continental United States, 162 Candida albicans isolates were fingerprinted with the species-specific probe Ca3 and the patterns were analyzed for relatedness with a computer-assisted system. The results demonstrate that particular BSI strains are more highly concentrated in particular geographic locales and that established BSI strains are endemic in some, but not all, hospitals in the study and undergo microevolution in hospital settings. The results, however, indicate no close genetic relationship among fluconazole-resistant BSI isolates in the collection, either from the same geographic locale or the same hospital. This study represents the first of three fingerprinting studies designed to analyze the origin, genetic relatedness, and drug resistance of Candida isolates responsible for BSI.

scholarly journals Rapid, Transient Fluconazole Resistance in Candida albicans Is Associated with Increased mRNA Levels ofCDR

1999 ◽  
Vol 43 (2) ◽  
pp. 438-438
Author(s):  
Kieren A. Marr ◽  
Christopher N. Lyons ◽  
Tige R. Rustad ◽  
Raleigh A. Bowden ◽  
Theodore C. White
Keyword(s):  
Candida Albicans ◽  
Mrna Levels ◽  
Fluconazole Resistance

scholarly journals Mechanisms and Advances in Anti-Ovarian Cancer with Natural Plants Component

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 5949
Author(s):  
Jingyuan Wu ◽  
Tuoyu Zhou ◽  
Yinxue Wang ◽  
Yanbiao Jiang ◽  
Yiqing Wang
Keyword(s):  
Ovarian Cancer ◽  
Drug Resistance ◽  
Molecular Mechanisms ◽  
Malignant Tumors ◽  
Multiple Drug Resistance ◽  
Multiple Drug ◽  
Therapeutic Effects ◽  
Dna Lesion ◽  
Female Reproductive Health ◽  
Wide Availability

Ovarian cancer ranks seventh in the most common malignant tumors among female disease, which seriously threatens female reproductive health. It is characterized by hidden pathogenesis, missed diagnosis, high reoccurrence rate, and poor prognosis. In clinic, the first-line treatment prioritized debulking surgery with paclitaxel-based chemotherapy. The harsh truth is that female patients are prone to relapse due to the dissemination of tumor cells and drug resistance. In these circumstances, the development of new therapy strategies combined with traditional approaches is conductive to improving the quality of treatment. Among numerous drug resources, botanical compounds have unique advantages due to their potentials in multitarget functions, long application history, and wide availability. Previous studies have revealed the therapeutic effects of bioactive plant components in ovarian cancer. These natural ingredients act as part of the initial treatment or an auxiliary option for maintenance therapy, further reducing the tumor and metastatic burden. In this review, we summarized the functions and mechanisms of natural botanical components applied in human ovarian cancer. We focused on the molecular mechanisms of cell apoptosis, autophagy, RNA and DNA lesion, ROS damage, and the multiple-drug resistance. We aim to provide a theoretical reference for in-depth drug research so as to manage ovarian cancer better in clinic.

scholarly journals Overexpression of Erg11p by the RegulatableGAL1 Promoter Confers Fluconazole Resistance inSaccharomyces cerevisiae

1999 ◽  
Vol 43 (11) ◽  
pp. 2798-2800 ◽  
Author(s):  
Dimitrios P. Kontoyiannis ◽  
Namita Sagar ◽  
Kendal D. Hirschi
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Candida Albicans ◽  
Azole Resistance ◽  
Fluconazole Resistance ◽  
Target Enzyme

ABSTRACT The contribution of the dosage of target enzyme P-450 14α-demethylase (14αDM) to fluconazole resistance in bothCandida albicans and Saccharomyces cerevisiaeremains unclear. Here, we show that overexpression ofSaccharomyces P-450 14αDM in S. cerevisiae, under the control of the regulatable promoter GAL1, results in azole resistance.

Sign in / Sign up

Export Citation Format

Share Document