Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Azoles”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1999

In-vitro resistance to azoles associated with mitochondrial DNA deficiency in Candida glabrata.

A commercially available disk diffusion procedure was used in a large-scale study to evaluate the susceptibility of a wide range of Candida isolates to polyenes and azoles. With almost all isolates of C. glabrata resistant colonies were present within the inhibition zones for the azole compounds fluconazole, ketoconazole and miconazole, and less frequently for isoconazole, econazole and clotrimazole. Ten randomly selected isolates were cloned by limiting dilution and the susceptibility of the resulting strains to polyenes and azoles was determined. All strains presented a similar susceptibility pattern with sensitivity to polyenes and the presence of resistant colonies for all azole compounds except tioconazole. For each strain and each antifungal agent, one of these resistant colonies was subcultured and studied for antifungal susceptibility. All these colonies showed similar properties regardless of which antifungal agent allowed their selection, with increased sensitivity to polyenes and cross-resistance to the azole compounds except tioconazole. Similar results were obtained on Shadomy's modified medium and on synthetic medium. Likewise, determination of MICs by the Etest method confirmed the resistance to fluconazole. Comparative growth studies revealed a respiratory deficiency in the mutants caused by mitochondrial DNA (mtDNA) deletions. In addition, 'petite' mutants were obtained from a wild-type strain by exposure to ethidium bromide, and these respiratory mutants were shown to be resistant to azoles. These results demonstrate the relationship between mtDNA deficiency and resistance to azoles, and provide an interesting model to study the mechanisms of action of these antifungal agents.

Antifungal Agents↗
PubMed1995

Mechanisms of resistance to azole antifungal agents in Candida albicans isolates from AIDS patients involve specific multidrug transporters.

Azole antifungal agents, and especially fluconazole, have been used widely to treat oropharyngeal candidiasis in patients with AIDS. An increasing number of cases of clinical resistance against fluconazole, often correlating with in vitro resistance, have been reported. To investigate the mechanisms of resistance toward azole antifungal agents at the molecular level in clinical C. albicans isolates, we focused on resistance mechanisms related to the cellular target of azoles, i.e., cytochrome P450(14DM) (14DM) and those regulating the transport or accumulation of fluconazole. The analysis of sequential isogenic C. albicans isolates with increasing levels of resistance to fluconazole from five AIDS patients showed that overexpression of the gene encoding 14DM either by gene amplification or by gene deregulation was not the major cause of resistance among these clinical isolates. We found, however, that fluconazole-resistant C. albicans isolates failed to accumulate 3H-labelled fluconazole. This phenomenon was reversed in resistant cells by inhibiting the cellular energy supply with azide, suggesting that resistance could be mediated by energy-requiring efflux pumps such as those described as ATP-binding cassette (ABC) multidrug transporters. In fact, some but not all fluconazole-resistant clinical C. albicans isolates exhibited up to a 10-fold relative increase in mRNA levels for a recently cloned ABC transporter gene called CDR1. In an azole-resistant C. albicans isolate not overexpressing CDR1, the gene for another efflux pump named BENr was massively overexpressed. This gene was cloned from C. albicans for conferring benomyl resistance in Saccharomyces cerevisiae. Therefore, at least the overexpression or the deregulation of these two genes potentially mediates resistance to azoles in C. albicans clinical isolates from AIDS patients with oropharyngeal candidiasis. Involvement of ABC transporters in azole resistance was further evidenced with S. cerevisiae mutants lacking specific multidrug transporters which were rendered hypersusceptible to azole derivatives including fluconazole, itraconazole, and ketoconazole.

AIDS-Related Opportunistic Infections↗
PubMed1999

Antagonism of azole activity against Candida albicans following induction of multidrug resistance genes by selected antimicrobial agents.

Antifungal azoles (e.g., fluconazole) are widely used for prophylaxis or treatment of Candida albicans infections in immunocompromised individuals, such as those with AIDS. These individuals are frequently treated with a variety of additional antimicrobial agents. Potential interactions between three azoles and 16 unrelated drugs (antiviral, antibacterial, antifungal, and antiprotozoal agents) were examined in vitro. Two compounds, tested at concentrations achievable in serum, demonstrated an antagonistic effect on azole activity against C. albicans. At fluconazole concentrations two to four times the 50% inhibitory concentration, C. albicans growth (relative to treatment with fluconazole alone) increased 3- to 18-fold in the presence of albendazole (2 microg/ml) or sulfadiazine (50 microg/ml). Antagonism (3- to 78-fold) of ketoconazole and itraconazole activity by these compounds was also observed. Since azole resistance has been correlated with overexpression of genes encoding efflux proteins, we hypothesized that antagonism results from drug-induced overexpression of these same genes. Indeed, brief incubation of C. albicans with albendazole or sulfadiazine resulted in a 3-to->10-fold increase in RNAs encoding multidrug transporter Cdr1p or Cdr2p. Zidovudine, trimethoprim, and isoniazid, which were not antagonistic with azoles, did not induce these RNAs. Fluphenazine, a known substrate for Cdr1p and Cdr2p, strongly induced their RNAs and, consistent with our hypothesis, strongly antagonized azole activity. Finally, antagonism was shown to require a functional Cdr1p. The possibility that azole activity against C. albicans is antagonized in vivo as well as in vitro in the presence of albendazole and sulfadiazine warrants investigation. Drug-induced overexpression of efflux proteins represents a new and potentially general mechanism for drug antagonism.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Inhibitory effect of azole antifungal agents on the glucuronidation of lorazepam using rabbit liver microsomes in vitro.

Azole antifungal agents (azoles) have inhibitory effects on the cytochrome P450. However, the effect of azoles on conjugative metabolism has not been given much attention. Lorazepam (LZP), a benzodiazepine sedative agent, is known to be metabolized by uridine 5'-diphosphate (UDP)-glucuronyltransferase. Herein we report investigation of the effect of azoles on the enzyme-kinetics of glucuronidation of lorazepam using rabbit liver microsomes in vitro. The Km and Vmax for LZP glucuronidation were determined to be 0.26+/-0.08 mM and 1.25+/-0.21 nmol/min/mg protein, respectively, when evaluated in the presence of a detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) (0.8 mg/mg protein). Azoles fluconazole, miconazole, and ketoconazole competitively inhibited the glucuronidation of LZP, with Ki values of 7.17+/-4.78 mM, 0.17+/-0.08 mM, and 0.092+/-0.026 mM, respectively. These results are comparable to the previously reported Ki values of azoles with zidovudine (AZT) glucuronidation (1.4, 0.18, and 0.08 mM for fluconazole, miconazole, and ketoconazole, respectively) [Sampol et al., Br. J. Clin. Pharmacol., 40, 83-86, 1995]. Therefore, in order to avoid possible side effects of LZP, the concomitant administration of LZP and azoles should be carefully evaluated.

Animals↗
PubMed1997

Unresponsive HIV-related oro-oesophageal candidosis--an evaluation of two new in-vitro azole susceptibility tests.

Azole-resistant HIV-related candidosis is increasingly recognized. We evaluated two new in-vitro susceptibility tests (the NCCLS proposed MIC method and Odds' assessment of relative growth in single anti-fungal concentration) as predictors of the clinical outcome of 66 HIV-positive patients with oral candidosis, of whom 22 were azole naive, 27 had always previously responded to azole therapy and 17 had persistent candidosis unresponsive to 7 days of standard azole therapy. None of the last group responded to increased daily doses of fluconazole or itraconazole capsules, though nine responded to itraconazole cyclodextrin solution 200 mg bd for 7 days. Our findings suggest that agreement between the Odds' test and the MIC method was excellent (96-98%) and that both could discriminate between isolates of azole-unresponsive patients and those of azole-responsive patients. For fluconazole susceptibility an MIC > or = 8 mg/L detected fluconazole-unresponsive patients with a sensitivity of 94% and specificity of 100%; Odds' method achieved 100% sensitivity and 100% specificity using all cut-offs between 77 and 88% relative growth in medium containing fluconazole (10(-5) M; 3 mg/L). For itraconazole and ketoconazole agreement between MIC and Odds' method was again excellent (98% and 96%, respectively) but five azole-unresponsive patients appeared to have ketoconazole-susceptible organisms as defined by both tests, and similarly 11 appeared to have itraconazole-susceptible organisms by both tests despite failing to respond to the capsule formulation of the drug. Of these 11, eight responded to itraconazole solution; this finding implies that itraconazole capsule failure might represent poor drug absorption rather than fungal resistance.

AIDS-Related Opportunistic Infections↗
PubMed2002

Azole susceptibility patterns and genetic relationship among oral Candida strains isolated in the era of highly active antiretroviral therapy.

We performed a cross-sectional study to analyze patterns of azole susceptibility of oral isolates in the highly active antiretroviral therapy (HAART) era and compared current data with those obtained for isolates from 1994. We further identified patients with relapsing oral pharyngeal candidiasis (OPC) who had been included in a similar study in 1994. For these subjects, we compared the susceptibility pattern for the OPC isolates, and if a modification of azole resistance was observed, we analyzed the genotypic pattern for the 1994 and 2000 isolates to determine whether the dominant strain was closely related. We included 69 consecutive HIV-infected subjects with 137 episodes of OPC who were admitted to our ward from January to June 2000. Ninety-two strains (67%) and 21 non- strains (15%) were isolated. We identified 24 episodes of OPC caused by two different species. Compared with the pre-HAART era, the fluconazole resistance of isolates significantly decreased from 45% to 10% (p <.001). Itraconazole resistance decreased from 37% to 7% (p <.001). Ketoconazole resistance (3% in 1994) was not detected more. Nine patients whose isolate was susceptible to all azole drugs had a previous isolate resistant to all azole drugs. We observed that these isolates exhibited different fingerprint profiles. Our findings demonstrate that most cases of HIV-associated OPC observed in the HAART era are caused by azole-susceptible strains. The reversion of an isolate from azole resistant to azole susceptible is related to strain replacement.

AIDS-Related Opportunistic Infections↗
PubMed1997

Cloning of Candida albicans genes conferring resistance to azole antifungal agents: characterization of CDR2, a new multidrug ABC transporter gene.

Resistance to azole antifungal agents in Candida albicans can be mediated by multidrug efflux transporters. In a previous study, we identified at least two such transporters, Cdr1p and Benp, which belong to the class of ATP-binding cassette (ABC) transporters and of major facilitators, respectively. To isolate additional factors potentially responsible for resistance to azole antifungal agents in C. albicans, the hypersusceptibility of a Saccharomyces cerevisiae multidrug transporter mutant, delta pdr5, to these agents was complemented with a C. albicans genomic library. Several new genes were isolated, one of which was a new ABC transporter gene called CDR2 (Candida drug resistance). The protein Cdr2p encoded by this gene exhibited 84% identity with Cdr1p and could confer resistance to azole antifungal agents, to other antifungals (terbinafine, amorolfine) and to a variety of metabolic inhibitors. The disruption of CDR2 in the C. albicans strain CAF4-2 did not render cells more susceptible to these substances. When the disruption of CDR2 was performed in the background of a mutant in which CDR1 was deleted, the resulting double delta cdr1 delta cdr2 mutant was more susceptible to these agents than the single delta cdr1 mutant. The absence of hypersusceptibility of the single delta cdr2 mutant could be explained by the absence of CDR2 mRNA in azole-susceptible C. albicans strains. CDR2 was overexpressed, however, in clinical C. albicans isolates resistant to azole antifungal agents as described previously for CDR1, but to levels exceeding or equal to those reached by CDR1. Interestingly, CDR2 expression was restored in delta cdr1 mutants reverting spontaneously to wild-type levels of susceptibility to azole antifungal agents. These data demonstrate that CDR2 plays an important role in mediating the resistance of C. albicans to azole antifungal agents.

ATP-Binding Cassette Transporters↗
PubMed1987

Sterols in Candida albicans mutants resistant to polyene or azole antifungals, and of a double mutant C. albicans 6.4.

Investigations of resistant mutants could help resolve differences and similarities in the action of azole and polyene antifungals whose modes of action are related; both disrupt membrane properties, such as permeability, by interfering with membrane sterols--polyenes by direct binding and azoles by inhibiting their synthesis. Studies of laboratory-derived mutants of Candida albicans which have an altered sterol content and/or an altered sterol composition do not provide evidence for a unified mechanism of polyene resistance. Clinical isolates of azole-resistant C. albicans have an increased or unaltered content of ergosterol and are impermeable to azoles. C. albicans 6.4, a laboratory-derived mutant resistant to both polyenes and azoles, is impermeable to azoles and has an increased content of methylated sterols. This unusual sterol composition resembles that of sensitive strains grown in the presence of azoles and may prevent polyene binding.

Antifungal Agents↗
PubMed1988

Cytochrome P450 of fungi: primary target for azole antifungal agents.

Cytochromes of fungi are essentially similar to those of animals. Cytochromes of fungi constitute two electron transport systems occurring in mitochondria and the endoplasmic reticulum. The former system, called the respiratory chain, contributes to cellular respiration and ATP generation, whereas the later system, named the microsomal electron transport system, is responsible for biosynthesis of several cellular components. The oxidative metabolism of lanosterol, that is included in the biosynthetic pathway of ergosterol, is one of the important functions of the microsomal electron transport system, which is catalyzed by P450(14DM). Many azole antifungal agents avidly combine with P450(14DM) and inhibit the oxidative removal of C-32 (the 14 alpha-demethylation) of lanosterol. This inhibition causes depletion of ergosterol and accumulation of 14-methylsterols in the membrane of fungal cells. Such change in sterol composition disturbs membrane function and results in growth inhibition and death of the fungal cells. Accordingly, P450(14DM) is considered as the primary target for azole antifungal agents. Cytochrome P450, which mediates the 14 alpha-demethylation of lanosterol, is also present in mammalian cells. Mammalian cells contain various species of cytochrome P450 which are responsible for many important cellular metabolic functions. If azole antifungal agents inhibit mammalian cytochrome P450 too, their systemic use may result in potentially significant adverse reactions. The high selectivity of azole antifungal agents for fungal P450(14DM) will be necessary for their systemic application. Binding ability of an azole antifungal agent to P450(14DM) is predominantly determined by the substituent at N-1 of the azole group, and the substituent must interact with the substrate site of the cytochrome. Extensive modification of the N-1 substituents and the screening of newly developed compounds with respect to the selectivity to fungal P450(14DM) with some conventional methods will be necessary. For this project, a biochemical understanding of cytochrome P450 and other cytochromes is important.

Animals↗
PubMed2006

Structure-based optimization of azole antifungal agents by CoMFA, CoMSIA, and molecular docking.

In a continuing effort to develop highly potent azole antifungal agents, the three-dimensional quantitative structure-activity relationship methods, CoMFA and CoMSIA, were applied using a set of novel azole antifungal compounds. The binding mode of the compounds at the active site of lanosterol 14alpha-demethylase was further explored using the flexible docking method. Various hydrophobic, van der Waals, pi-pi stacking, and hydrogen bonding interactions were observed between the azoles and the enzyme. Based on results from the molecular modeling, a receptor-based pharmacophore model was established to guide the rational optimization of the azole antifungal agents. Thus, a total of 57 novel azoles were designed and synthesized by a three-step optimization process. In vitro antifungal assay revealed that the antifungal activities of these novel azoles were greatly improved, which confirmed the reliability of the model from molecular modeling.

Antifungal Agents↗
PubMed2000

Sensitizing capacity of azole derivatives: Part III. Investigations with anthelmintics, antimycotics, fungicides, antithyroid compounds, and proton pump inhibitors.

BACKGROUND: More than hundred azole derivatives are used today for different purposes. The majority possess antimycotic, antibacterial, anthelmintic, and antiprotozoal properties. They are used as agricultural fungicides; topical antimycotics, and, for example, in antidandruff cosmetics. More recently the antithyroid and antiulcerative activity of certain imimidazoles and benzimidazoles also has been proven, which led to the introduction of proton pump inhibitors and antithyroid drugs to the market. OBJECTIVE: Case reports from the literature and experimental studies suggest that some of the azole derivatives possess a distinct sensitizing potency. Occupational exposure either in the pharmaceutical manufacture or in the pesticide's application by farmers caused allergic contact dermatitis (ACD). However, experimental studies in guinea pigs to determine their sensitizing capacity have been performed only sporadically. METHOD: Guinea pigs were sensitized by a modified Freund's complete adjuvant (FCA) method, with 35 azoles used as agricultural fungicides, proton pump inhibitors, antimycotics, antithyroid agents, antiprotozoals, antimicrobials, anthelmintics, and wood preservatives. RESULTS: Four azoles exhibited a strong sensitizing capacity, 3 a moderate, and 11 a weak sensitizing capacity. Seventeen derivatives remained negative. Among the strong sensitizers were the 3 proton pump inhibitors omeprazole, pantoprazole, and rabeprazole, as well as the antithyroid drug carbimazole. The latter displayed the highest sensitizing power (mean response = 2.50) of all 62 azole derivatives investigated in the present and the 2 previous experimental studies. CONCLUSION: As long as the strong sensitizing azoles are used only systemically the risk of acquiring contact hypersensitivity is low. However, if the idea should arise to use them topically, for example in ointments, tinctures, or lotions against fungal infections, skin problems will probably be observed abundantly.

Animals↗
PubMed2004

Comparative assessment of the inhibition of recombinant human CYP19 (aromatase) by azoles used in agriculture and as drugs for humans.

Azoles (imidazoles and triazoles) are used as antifungal agents in agriculture and in medicine, and also for antiestrogen therapy, e.g., for breast cancer treatment. Antifungal activity is based on inhibition of fungal CYP51 (lanosterol 14alpha-demethylase), and estrogen biosynthesis reduction is due to azole inhibition of CYP19 (aromatase). Inhibition of aromatase by antifungal agents is usually an unwanted side effect and may cause endocrine disruption. A fluorimetric assay based on human recombinant CYP19 enzyme with dibenzylfluorescein as a substrate was used to compare the inhibitory potency of 22 azole compounds. Dose responses were established and duplicate datasets were analyzed with a nonlinear mixed-effects model with cumulative normal distribution for the logarithm of concentration. IC50 values (50% inhibitory concentration) of 13 fungicides used in agriculture ranged more than 700-fold, starting from 0.047 microM. The potency of seven human drugs spanned more than 7000-fold, starting from 0.019 microM. Most potent fungicides included prochloraz, flusilazole, and imazalil, and most potent medicinal antifungals were bifonazole, miconazole, and clotrimazole. These in vitro data indicate that the top-ranking azoles used as antifungal agents or drugs are as potent inhibitors of aromatase as are antiestrogen therapeutics used to treat breast cancer. These putative effects of azole agents and drugs on steroid biosynthesis and sex hormone balance should be considered when used in human subjects and also in wildlife exposed to azole fungicides used in agriculture.

Agrochemicals↗
PubMed2006

Antifungal prophylaxis with azoles in high-risk, surgical intensive care unit patients: a meta-analysis of randomized, placebo-controlled trials.

OBJECTIVE: The use of antifungal prophylaxis remains controversial in most populations including surgical intensive care unit patients. A meta-analysis of randomized controlled trials was performed to evaluate the safety and effectiveness of azoles as antifungal prophylaxis in high-risk patients receiving treatment in the surgical intensive care unit. DATA SOURCE: Data were obtained from PubMed, Current Contents, Cochrane central register of controlled trials, and references from relevant articles. STUDY SELECTION: Randomized controlled trials using azoles as antifungal prophylaxis vs. placebo were included in the study. DATA EXTRACTION: Two independent reviewers extracted data concerning the development of fungal infections (superficial or invasive), adverse effects, and mortality. SYNTHESIS: Six randomized controlled trials were included in the main analysis. Publication bias and statistically significant heterogeneity were not observed among the analyzed studies. Patients receiving antifungal prophylaxis developed fewer episodes of candidemia (odds ratio [OR] = 0.28, 95% confidence interval [CI] 0.09-0.86), nonbloodstream invasive fungal infections (OR = 0.26, 95% CI 0.12-0.53), and noninvasive (superficial) fungal infections (OR = 0.22, 95% CI 0.11-0.43), respectively. No reduction in mortality was observed among patients who received azole prophylaxis (OR = 0.74, 95% CI 0.52-1.05). There was no significant difference in reported adverse effects (OR = 1.28, 95% CI 0.82-1.98). CONCLUSIONS: Despite its limitations, our meta-analysis suggests that the prophylactic use of azoles in high-risk surgical intensive care unit patients is associated with a reduction of fungal infections but not in all-cause mortality. However, although not noted in the analyzed randomized controlled trials, there is concern about the use of azoles due to possible shift toward non-albicans species and development of resistance to azoles.

Antifungal Agents↗
PubMed1997

Studies of the mechanism of human salivary histatin-5 candidacidal activity with histatin-5 variants and azole-sensitive and -resistant Candida species.

Histatins are a group of small, cationic, antifungal peptides present in human saliva. A previous molecular modeling analysis suggested structural similarity between the Phe14-His15 and His18-His19 dipeptide sequences in histatin-5 (Hsn-5; a 24-amino-acid polypeptide) and the sequence of miconazole (one of the azole-based antifungal therapeutic agents), implying that the mechanisms of killing of Candida albicans by these two molecules may be similar. To further elaborate on this observation, we have produced two variants of Hsn-5 in which Phe14-His15 or His18-His19 dipeptide sequences were replaced by Ala-Ala (F14A/H15A and H18A/H19A) to eliminate the phenyl and imidazole rings of the side chains and assessed their candidacidal activities against C. albicans. In addition, we tested azole-resistant C. albicans and Candida glabrata strains for their susceptibilities to Hsn-5. Analysis of the purified recombinant proteins for their candidacidal activities indicated that both variants were significantly less effective (the molar concentrations required to kill half of the maximum number of cells [ED50s], approximately 67 and approximately 149 microM for F14A/H15A and H18A/H19A, respectively) than the unaltered Hsn-5 (ED50, approximately 8 microM) at killing C. albicans, suggesting that the two dipeptide sequences are important for the candidacidal activity of Hsn-5. Assessment of the candidacidal activity of Hsn-5 with the well-characterized azole-resistant strains of C. albicans and C. glabrata, however, suggested that the mode of action of histatins against Candida is distinct from that of azole-based antifungal agents because Hsn-5 kills both azole-sensitive and azole-resistant strains equally well.

Amino Acids↗
PubMed1998

Induction of resistance to azole drugs in Trypanosoma cruzi.

Trypanosoma cruzi is the protozoan parasite that causes Chagas' disease, a frequently fatal illness affecting the heart and gastrointestinal systems. An estimated 16 million to 18 million people in Latin America and 50,000 to 100,000 people in the United States are infected with this pathogen. Treatment options for T. cruzi infections are suboptimal due to the toxicities and limited effectiveness of the available drugs. Azole antimicrobial agents have been discovered to have antitrypanosomal activity by inhibition of ergosterol synthesis. The triazole itraconazole was recently shown to produce a parasitologic cure rate of 53% in chronically infected patients (W. Apt et al., Am. J. Trop. Med. Hyg. 59:133-138, 1998), a result which may lead to more use of this family of drugs for the treatment of T. cruzi infections. In the experiments reported on here, resistance to azoles was induced in vitro by serial passage of mammalian-stage parasites in the presence of fluconazole for 4 months. These parasites were cross resistant to the other azoles, ketoconazole, miconazole, and itraconazole. They remained susceptible to benznidazole and amphotericin B. The azole-resistant phenotype was stable for more than 2 months of in vitro serial passage without fluconazole. In addition, the parasites resisted treatment in mice receiving ketoconazole. The rapid development of azole resistance in T. cruzi in vitro suggests that resistance to azole drugs has the potential to occur in patients and may pose an impediment to the progress being made in the treatment of T. cruzi infection.

Animals↗
PubMed2002

Interaction of common azole antifungals with P glycoprotein.

Both eucaryotic and procaryotic cells are resistant to a large number of antibiotics because of the activities of export transporters. The most studied transporter in the mammalian ATP-binding cassette transporter superfamily, P glycoprotein (P-gp), ejects many structurally unrelated amphiphilic and lipophilic xenobiotics. Observed clinical interactions and some in vitro studies suggest that azole antifungals may interact with P-gp. Such an interaction could both affect the disposition and exposure to azole antifungal therapeutics and partially explain the clinical drug interactions observed with some antifungals. Using a whole-cell assay in which the retention of a marker substrate is evaluated and quantified, we studied the abilities of the most widely prescribed orally administered azole antifungals to inhibit the function of this transporter. In a cell line presenting an overexpressed amount of the human P-gp transporter, itraconazole and ketoconazole inhibited P-gp function with 50% inhibitory concentrations (IC(50)s) of approximately 2 and approximately 6 microM, respectively. Cyclosporin A was inhibitory with an IC(50) of 1.4 microM in this system. Uniquely, fluconazole had no effect in this assay, a result consistent with known clinical interactions. The effects of these azole antifungals on ATP consumption by P-gp (representing transport activity) were also assessed, and the K(m) values were congruent with the IC(50)s. Therefore, exposure of tissue to the azole antifungals may be modulated by human P-gp, and the clinical interactions of azole antifungals with other drugs may be due, in part, to inhibition of P-gp transport.

3T3 Cells↗
PubMed2003

Genome-wide expression profile analysis reveals coordinately regulated genes associated with stepwise acquisition of azole resistance in Candida albicans clinical isolates.

Candida albicans is an opportunistic human fungal pathogen and a causative agent of oropharyngeal candidiasis (OPC), the most frequent opportunistic infection among patients with AIDS. Fluconazole and other azole antifungal agents have proven effective in the management of OPC; however, with increased use of these agents treatment failures have occurred. Such failures have been associated with the emergence of azole-resistant strains of C. albicans. In the present study we examined changes in the genome-wide gene expression profile of a series of C. albicans clinical isolates representing the stepwise acquisition of azole resistance. In addition to genes previously associated with azole resistance, we identified many genes whose differential expression was for the first time associated with this phenotype. Furthermore, the expression of these genes was correlated with that of the known resistance genes CDR1, CDR2, and CaMDR1. Genes coordinately regulated with the up-regulation of CDR1 and CDR2 included the up-regulation of GPX1 and RTA3 and the down-regulation of EBP1. Genes coordinately regulated with the up-regulation of CaMDR1 included the up-regulation of IFD1, IFD4, IFD5, IFD7, GRP2, DPP1, CRD2, and INO1 and the down-regulation of FET34, OPI3, and IPF1222. Several of these appeared to be coordinately regulated with both the CDR genes and CaMDR1. Many of these genes are involved in the oxidative stress response, suggesting that reduced susceptibility to oxidative damage may contribute to azole resistance. Further evaluation of the role these genes and their respective gene products play in azole antifungal resistance is warranted.

Antifungal Agents↗
PubMed2005

Mechanisms of azole resistance in a clinical isolate of Candida tropicalis.

Azole resistance has been insufficiently investigated in the yeast Candida tropicalis. Here we determined the molecular mechanisms responsible for azole resistance in a clinical isolate of this pathogenic yeast. Antifungal susceptibility testing performed by a disk diffusion method showed resistance or markedly decreased susceptibility to azoles, which was confirmed by determination of MICs. Considering the relationship between azole susceptibility and the respiration reported for other yeast species, the respiratory activity of this isolate was investigated. Flow cytometry using rhodamine 123 and oxygraphy demonstrated an increased respiratory activity, which was not linked to an overexpression or increased number of copies of the mitochondrial genome. Among previously described resistance mechanisms, an increased activity of efflux pumps was investigated by flow cytometry using rhodamine 6G. However, the efflux of rhodamine 6G was lower in the resistant isolate than in susceptible ones. Likewise, real-time reverse transcription-PCR quantification of the expression of C. tropicalis MDR1 (CtMDR1), which encodes an efflux protein belonging to the major facilitator superfamily, did not show overexpression of this gene. In contrast, the resistant isolate overexpressed the CtERG11 gene coding for lanosterol 14alpha-demethylase. This was in agreement with the larger amount of ergosterol found in this isolate. Moreover, sequencing of CtERG11 showed a point mutation leading to a tyrosine substitution in the protein sequence, which might lead to decreased binding affinity for azoles. In conclusion, overexpression of CtERG11 associated with a missense mutation in this gene seemed to be responsible for the acquired azole resistance of this clinical isolate.

Azoles↗