Typing ofCandida albicansstrains

Formyl-Peptide Receptor 2 Signaling Modulates SLC7A11/xCT Expression and Activity in Tumor Cells

Cancer cells exhibit high levels of oxidative stress and consequently require a high amount of cysteine for glutathione synthesis. Solute Carrier Family 7 Member 11 (SLC7A11), or xCT, mediates the cellular uptake of cystine in exchange for intracellular glutamate; imported extracellular cystine is reduced to cysteine in the cytosol through a NADPH-consuming reduction reaction. SLC7A11/xCT expression is under the control of stress-inducing conditions and of several transcription factors, such as NRF2 and ATF4. Formyl-peptide receptor 2 (FPR2) belongs to the FPR family, which transduces chemotactic signals mediating either inflammatory or anti-inflammatory responses according to the nature of its ligands and/or FPR2 binding with other FPR isoforms. The repertoire of FPR2 agonists with anti-inflammatory activities comprises WKYMVm peptide and Annexin A1 (ANXA1), and the downstream effects of the intracellular signaling cascades triggered by FPR2 include NADPH oxidase (NOX)-dependent generation of reactive oxygen species. Herein, we demonstrate that stimulation of CaLu-6 cells with either WKYMVm or ANXA1: (i) induces the redox-regulated activation of SLC7A11/xCT; (ii) promotes the synthesis of glutathione; (iii) prevents lipid peroxidation; and (iv) favors NRF2 nuclear translocation and activation. In conclusion, our overall results demonstrate that FPR2 agonists and NOX modulate SLC7A11/xCT expression and activity, thereby identifying a novel regulative pathway of the cystine/glutamate antiport that represents a new potential therapeutical target for the treatment of human cancers.

Genetic variability analysis among clinical Candida spp. isolates using random amplified polymorphic DNA

The patterns of genetic variation of samples of Candida spp. isolated from patients infected with human immunodeficiency virus in Vitória, state of Espírito Santo, Brazil, were examined. Thirty-seven strains were isolated from different anatomical sites obtained from different infection episodes of 11 patients infected with the human immunodeficiency virus (HIV). These samples were subjected to randomly amplified polymorphic DNA (RAPD) analysis using 9 different primers. Reproducible and complex DNA banding patterns were obtained. The experiments indicated evidence of dynamic process of yeast colonization in HIV-infected patients, and also that certain primers are efficient in the identification of species of the Candida genus. Thus, we conclude that RAPD analysis may be useful in providing genotypic characters for Candida species typing in epidemiological investigations, and also for the rapid identification of pathogenic fungi.

Molecular typing of Candida isolates from patients hospitalized in an intensive care unit

OBJECTIVES

The aim of our study was the molecular typing of 40 clinical isolates of Candida spp. obtained from patients with burns or trauma hospitalized in the intensive care unit of a general hospital.

METHODS

Isolates were recovered from blood, deep trauma, urine, sputum or from environment within a short period of time (4 months). The yeasts were identified using commercial yeast identification kits as C. albicans (17 isolates), C. tropicalis (16 isolates) and C. parapsilosis (10 isolates). The epidemiological relation of the isolates was tested with the Random Amplified Polymorphic DNA assay using three or four arbitrary chosen primers.

RESULTS

All C. albicans isolates presented distinct RAPD profiles, C. tropicalis isolates presented both the same and distinct RAPD patterns and the C. parapsilosis isolates presented the same RAPD pattern. All the environmental isolates were identified as C. parapsilosis and they had the same RAPD pattern as C. parapsilosis clinical isolates. Candida parapsilosis delineation was confirmed with PFGE.

CONCLUSIONS

The colonization/infection with C. albicans was endogenous, the C. tropicalis colonization/infection was both endogenous and exogenous, and the C. parapsilosis colonization/infection had an environmental origin.

Differentiation of Candida strains by lectin-mediated agglutination kinetics

The lectin-mediated agglutination kinetics of Candida albicans, Candida tropicalis, Candida glabrata, Candida krusei, Candida kefyr, and Candida parapsilosis strains isolated from immunocompromised patients was investigated. The rate of the lectin-induced cell agglutination depends on the physiological state of the yeast cell population. Therefore, the Candida strains have to be cultivated and investigated under identical conditions. Lentil lectin (prepared from Lens culinaris), castor lectin, and concanavalin A were used. Different yeast species showed different agglutination behaviour. Furthermore, the lectin-mediated rate of agglutination is a strain-specific property which makes it possible to distinguish between different yeast strains of the same species. It is concluded that the lectin-mediated agglutination kinetics allows reproducible differentiation of yeast strains of the same species.

Genetic structure of typical and atypical populations of Candida albicans from Africa

Atypical isolates of the pathogenic yeast Candida albicans have been reported with increasing frequency. To investigate the origin of a set of atypical isolates and their relationship to typical isolates, we employed a combination of molecular phylogenetic and population genetic analyses using rDNA sequencing, PCR fingerprinting, and analysis of co-dominant DNA nucleotide polymorphisms to characterize the population structure of one typical and two atypical populations of C. albicans from Angola and Madagascar. The extent of clonality and recombination was assessed in each population. The analyses revealed that the structure of all three populations of C. albicans was predominantly clonal but, as in previous studies, there was also evidence for recombination. Allele frequencies differed significantly between the typical and the atypical populations, suggesting very low levels of gene flow between them. However, allele frequencies were quite similar in the two atypical C. albicans populations, suggesting that they are closely related. Phylogenetic analysis of partial sequences encoding the nuclear 26S rDNA demonstrated that all three populations belong to a single monophyletic group, which includes the type strain of C. albicans.

Transmission of an azole-resistant isogenic strain of Candida albicans among human immunodeficiency virus-infected family members with oropharyngeal candidiasis

We report transmission of an azole-resistant, isogenic strain of Candida albicans in a human immunodeficiency virus (HIV)-infected family of two children with symptomatic oropharyngeal candidiasis and a mother with asymptomatic colonization over a 5-year period. These findings were confirmed by three different molecular epidemiology methods: interrepeat PCR, Southern hybridization with a C. albicans repetitive element 2 probe, and electrophoretic karyotyping. This study contributes to an evolving understanding of the mode of transmission of C. albicans, particularly in children, and underscores the importance of monitoring specimens from family members of HIV-infected patients.

Evaluation of an optimized system for random amplified polymorphic DNA (RAPD)-analysis for genotypic mapping of Candida albicans strains

A simple, rapid, and cost-effective protocol has been developed for a PCR-based molecular typing method for Candida albicans, which includes the use of a commercially available medium (Chelex 100 Resin) for DNA extraction and a single set of two arbitrarily chosen oligonucleotide (10 nt length) primers for random amplified DNA(RAPD)-analysis. The optimized parameters for the amplification components and conditions for the selected primer combination have been determined to avoid artifactual variation (absence/presence of bands) in RAPD banding patterns in repeated assays. The optimized RAPD-assay consistently generated DNA-patterns of 33 genetically unrelated C. albicans isolates that contained ten polymorphic markers in the non-artifactual banding patterns. The intralaboratory reproducibility of RAPD patterns was efficient and consistent provided the optimized amplification conditions were rigidly controlled. Interlaboratory reproducibility was tempered by slight variations in time of cyclers of different thermocyclers. In comparison, the RAPD assay was almost equal to restriction enzyme analysis (REA) (Eco RI digested chromosomal DNA) in discrimination, and the RAPD assay was able to group isolates of C. albicans that were untypable by REA. The protocol outlined for an optimized RAPD-assay of C. albicans has the potential to be widely useful epidemiological screening tool that can be easily applied in the clinical laboratory.

Comparative study of the GenePath group 4 reagent system and other CHEF systems for karyotype analysis of Candida spp

The commercial GenePath Group 4 Reagent Candida kit (BioRad), designed to simplify the electrophoretic karyotyping of Candida spp. was evaluated against several other established contour-clamped homogeneous electric field (CHEF) systems for Candida. This comparison allowed assessment of both the GenePath system and the other CHEF systems regarding the sources of technical variability of the assays and variation in karyotypic analysis. The GenePath system appeared to be a simple, rapid and reliable tool for karyotyping of Candida spp. with a discriminatory power comparable with established CHEF systems. The evaluation showed that the variability of the CHEF systems for subtyping of Candida is largely a function of technical variabilities in the assay system (reagents, sample preparation, running conditions, and test performance), and of analytical variabilities due to imprecision or observers bias. Lack of standardization of these factors may contribute to variability among investigators and have an impact on the ultimate conclusions of an epidemiological study using CHEF methods.