Antifungal susceptibility and distribution of Candida spp. isolates from the University Hospital in the municipality of Dourados, State of Mato Grosso do Sul, Brazil

In vitro activity of four triazole antifungal drugs against clinically common and uncommon yeast species

Background and Purpose:

Incidence of fungal infections caused by opportunistic fungal pathogens, such as yeasts and yeast-like species, has undergone an increase in otherwise healthy individuals. These pathogens account for high mortality and show reduced susceptibility to the routine antifungal drugs. Accordingly, antifungal susceptibility testing is an urgent need in the determination of the susceptibility spectrum of antifungals and selection of appropriate antifungal agents for the management of patients with fungal infection.

Materials and Methods:

The present study was conducted on 110 yeast strains belonging to 15 species recovered from clinical specimens. Susceptibility of the isolates to four antifungal drugs (i.e., fluconazole, itraconazole, voriconazole, and posaconazole) was tested according to the Clinical and Laboratory Standards Institute guidelines M27-A3 and M27-S4.

Results:

Fluconazole exhibited no activity against 4.3% (n=2) of C. albicans isolates, whereas the remaining 44 isolates had a minimum inhibitory concentration (MIC) range of 0.125-4 μg/ml. Voriconazole had the lowest geometric mean MIC (0.03 µg/ml) against all isolated yeast species, followed by posaconazole (0.07 µg/ml), itraconazole (0.10 µg/ml), and fluconazole (0.60 µg/ml). Overall, all of the isolates had reduced voriconazole MICs with a MIC range of 0.016-0.5 μg/ml, except for one isolate of C. albicans that had a MIC of 1 μg/ml. Candida haemulonii as a multidrug-resistant fungus showed a fluconazole MIC of > 64 μg/ml.

Conclusion:

The current study provides insight into the antifungal susceptibility profiles of clinically common and uncommon yeast species to four triazole antifungal agents. According to our findings, voriconazole was the most active agent. Awareness about antifungal susceptibility patterns is highly helpful in the selection of appropriate antifungal drugs and identification of the efficiency of the currently used agents.

Bioinspired benzoxanthene lignans as a new class of antimycotic agents: synthesis and Candida spp. growth inhibition

In this work we synthetized the bioinspired benzoxanthene lignans (BXLs) 3, 14-22, and the phenazine derivative 23 as potential antimycotic agents. MICs and MFCs against Candida strains were determined. In a preliminary screening, compounds 3, 15, 20, 21, 22 were substantially inactive. Compounds 14 and 17 showed antifungal activity, being able to inhibit the growth of the majority of Candida strains with MIC values in the range 4.6-19.2 µM (14) and 26.0-104.3 µM (17); for three strains, the MICs were lower than those obtained using the antimycotic drug fluconazole. The three BXLs 18, 19 and 23 showed some MIC values lower than that of fluconazole; 18 was also active against two non-albicans Candida strains resistant to fluconazole. Phenazine 23, although active only against one strain (MIC = 1.3 µM), was one order of magnitude more potent than fluconazole. All the BXLs were fungicidal.

Characterisation of an ABC transporter of a resistant Candida glabrata clinical isolate

BACKGROUND

Candida glabrata ranks second in epidemiological surveillance studies, and is considered one of the main human yeast pathogens. Treatment of Candida infections represents a contemporary public health problem due to the limited availability of an antifungal arsenal, toxicity effects and increasing cases of resistance. C. glabrata presents intrinsic fluconazole resistance and is a significant concern in clinical practice and in hospital environments.

OBJECTIVE

The aim of this study was to characterise the azole resistance mechanism presented by a C. glabrata clinical isolate from a Brazilian university hospital.

METHODS

Azole susceptibility assays, chemosensitisation, flow cytometry and mass spectrometry were performed.

FINDINGS

Our study demonstrated extremely high resistance to all azoles tested: fluconazole, voriconazole, posaconazole and itraconazole. This isolate was chemosensitised by FK506, a classical inhibitor of ABC transporters related to azole resistance, and Rhodamine 6G extrusion was observed. A mass spectrometry assay confirmed the ABC protein identification suggesting the probable role of efflux pumps in this resistance phenotype.

MAIN CONCLUSIONS

This study emphasizes the importance of ABC proteins and their relation to the resistance mechanism in hospital environments and they may be an important target for the development of compounds able to unsettle drug extrusion.

Dectin-1 plays an important role in host defense against systemic Candida glabrata infection

Candida glabrata is the second most common pathogen of severe candidiasis in immunocompromised hosts, following C. albicans. Although C. glabrata and C. albicans belong to the same genus, they are phylogenetically distinct. C-type lectin receptors (CLRs), acting as pattern-recognition receptors (PRRs), play critical roles in host defense against C. albicans infections. However, our understanding of the specific roles of CLRs in host defense against C. glabrata is limited. Here, we explored the potential roles of the C-type lectins Dectin-1 and Dectin-2 in host defense against C. glabrata. We found that both Dectin-1-deficient mice (Dectin-1^-/-) and Dectin-2-deficient mice (Dectin-2^-/-) are more susceptible to C. glabrata infection. Dectin-1confers host higher sensitivity for sensing C. glabrata infections, while the effect of Dectin-2 in the host defense against C. glabrata is infection dose dependent. Dectin-1 is required for host myeloid cells recognition, killing of C. glabrata, and development of subsequent Th1 and Th17 cell-mediated adaptive immune response. Significantly impaired inflammatory responses such as inflammatory cells recruitment and cytokines release that were induced by C. glabrata were manifested in Dectin-1-deficient mice. Together, our study demonstrates that Dectin-1 plays an important role in host defense against systemic Candida glabrata infections, indicating a previous unknown control mechanism for this particular type of infection in host. Our study, therefore, provides new insights into the host defense against C. glabrata.

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

The azoles are the class of medications most commonly used to fight infections caused by Candida sp. Typically, resistance can be attributed to mutations in ERG11 gene (CYP51) which encodes the cytochrome P450 14α-demethylase, the primary target for the activity of azoles. The objective of this study was to identify mutations in the coding region of theERG11 gene in clinical isolates of Candidaspecies known to be resistant to azoles. We identified three new synonymous mutations in the ERG11 gene in the isolates of Candida glabrata (C108G, C423T and A1581G) and two new nonsynonymous mutations in the isolates of Candida krusei - A497C (Y166S) and G1570A (G524R). The functional consequence of these nonsynonymous mutations was predicted using evolutionary conservation scores. The G524R mutation did not have effect on 14α-demethylase functionality, while the Y166S mutation was found to affect the enzyme. This observation suggests a possible link between the mutation and dose-dependent sensitivity to voriconazole in the clinical isolate of C. krusei. Although the presence of the Y166S in phenotype of reduced azole sensitivity observed in isolate C. kruseidemands investigation, it might contribute to the search of new therapeutic agents against resistant Candida isolates.

Susceptibility pattern of Candida albicans isolated from Iranian patients to antifungal agents

Background and Purpose:

Candidiasis is a major fungal infection, and Candida albicans is the major cause of infections in humans. The Clinical and Laboratory Standards Institute (CLSI) developed new breakpoints for antifungal agents against C. albicans. In this multi-center study, we aimed to determine the drug susceptibility profile of C. albicans, isolated from Iranian population according to new species-specific CLSI.

Materials and Methods:

Clinical samples were cultured on Sabouraud dextrose agar and were incubated at room temperature for seven days. The isolates were transferred to Professor Alborzi Clinical Microbiology Research Center, Shiraz, Iran. C. albicans were identified by using API 20C AUX system. Broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) of amphotericin B, caspofungin, voriconazole, fluconazole, posaconazole, itraconazole, and ketoconazole, based on CLSI document M27-S4 and new breakpoints for some azoles and caspofungin.

Results:

Overall, 397 C. albicans were isolated from patients admitted to ten university hospitals in Iran. The MIC90 of the isolates to amphotericin B, caspofungin, voriconazole, fluconazole, posaconazole, itraconazole, and ketoconazole were 0.125, 0.125, 0.125, 1, 0.064, 0.5, and 0.125 µg/ml, and rates of resistance were 0.5%, 0.3%, 3.8%, 2.8%, and 2.5% for amphotericin B, caspofungin, voriconazole, fluconazole, and itraconazole, respectively.

Conclusion:

According to our data, fluconazole is the drug of choice for management of patients at risk for systemic candidiasis throughout the region, since it is cost-effective with low side effects.

Urinary tract infections and Candida albicans

Introduction

Urinary tract candidiasis is known as the most frequent nosocomial fungal infection worldwide. Candida albicans is the most common cause of nosocomial fungal urinary tract infections; however, a rapid change in the distribution of Candida species is undergoing. Simultaneously, the increase of urinary tract candidiasis has led to the appearance of antifungal resistant Candida species. In this review, we have an in depth look into Candida albicans uropathogenesis and distribution of the three most frequent Candida species contributing to urinary tract candidiasis in different countries around the world.

Material and methods

For writing this review, Google Scholar –a scholarly search engine– (http://scholar.google.com/) and PubMed database (http://www.ncbi.nlm.nih.gov/pubmed/) were used. The most recently published original articles and reviews of literature relating to the first three Candida species causing urinary tract infections in different countries and the pathogenicity of Candida albicans were selected and studied.

Results

Although some studies show rapid changes in the uropathogenesis of Candida species causing urinary tract infections in some countries, Candida albicans is still the most important cause of candidal urinary tract infections.

Conclusions

Despite the ranking of Candida albicans as the dominant species for urinary tract candidiasis, specific changes have occurred in some countries. At this time, it is important to continue the surveillance related to Candida species causing urinary tract infections to prevent, control and treat urinary tract candidiasis in future.

Frequency of clinically isolated strains of oral Candida species at Kagoshima University Hospital, Japan, and their susceptibility to antifungal drugs in 2006-2007 and 2012-2013

BACKGROUND

The isolation frequency and susceptibility to antifungal agents of oral Candida isolates from patients with oral candidiasis (OC) were compared between studies conducted in 2006-2007 and 2012-2013.

METHODS

A total158 strains was isolated from 112 patients who visited Kagoshima University Hospital for the treatment of OC during the 14-month period from February 2012 and March 2013, and evaluated on the isolation frequency of each Candida strain and the susceptibility against antifungal drugs as compared to those evaluated in 2006-2007.

RESULTS

There was a higher frequency of xerostomia as a chief complaint and of autoimmune disease in the 2012-2013 study than in the 2006-2007 study. More than 95% of Candida isolates were C. albicans and C. glabrata. In addition, the proportion of the latter increased from 12.3% in the 2006-2007 study to 23.4% in the 2012-2013 study, while the proportion of the former decreased from 86.2% to 72.8%, respectively. C. albicans was isolated in almost all patients, while C. glabrata was only isolated concomitantly with C. albicans. Minimal inhibitory concentrations (MICs) were not significantly different between groups with a few exceptions. Candida isolates, of which MICs surpassed break points, apparently increased for miconazole and itraconazole against C. glabrata in the 2012-2013 study, but this was not statistically significant. As a result, more cases of autoimmune disease, a greater number of C. glabrata isolates, and higher resistance to azoles were seen in the 2012-2013 study than in the 2006-2007 study.

CONCLUSION

These data indicate that with recent increases in C. glabrata infection, a causative fungus of OC, and in C. glabrata resistance to azoles, caution is needed in the selection of antifungal drugs for the treatment of OC.

Candida glabrata: a review of its features and resistance

Candida species belong to the normal microbiota of the oral cavity and gastrointestinal and vaginal tracts, and are responsible for several clinical manifestations, from mucocutaneous overgrowth to bloodstream infections. Once believed to be non-pathogenic, Candida glabrata was rapidly blamable for many human diseases. Year after year, these pathological circumstances are more recurrent and problematic to treat, especially when patients reveal any level of immunosuppression. These difficulties arise from the capacity of C. glabrata to form biofilms and also from its high resistance to traditional antifungal therapies. Thus, this review intends to present an excerpt of the biology, epidemiology, and pathology of C. glabrata, and detail an approach to its resistance mechanisms based on studies carried out up to the present.