Adhesion and cell-surface-hydrophobicity of sequentially isolated genetic isotypes of Candida albicans in an HIV-infected Southern Chinese cohort. Adharenz und Zelloberflachen-Hydrophobizitat von sequentiell isolierten genetischen Isotypen von Candida albicans aus einer HIV-infizierten sudchinesischen Kohorte

Genotypes and virulence-related activities of Candida albicans derived from oral cavity of patients in Hokkaido

OBJECTIVE

This study aimed to elucidate the difference in virulence of Candida albicans derived from oral candidiasis and non-oral candidiasis patients, and its genotype differences in Hokkaido to obtain a clue of a platform to develop new approaches for diagnosis and treatment.

DESIGN

C. albicans strains were collected from patients who visited the Hokkaido University Hospital Dental Center. Each strain was examined to i) identify the Candida albicans genotype by PCR, ii) measure the strain's extracellular secretory enzyme activity, iii) determine the strain's ability to induce the production of interleukin-8, and iv) determine the strain's ability to induce cell death.

RESULTS

Certain virulence-related protease activities and cytotoxicity were higher in strains derived from patients with oral candidiasis compared with strains derived from patients without oral candidiasis. This is the first report on genotypes and the virulence-related activities, such as some protease secretion, IL-8 induction and cytotoxicity of C. albicans in Hokkaido.

CONCLUSIONS

The virulence-related activities of the fungal strain may influence the pathogenesis of oral candidiasis, such as production of secreted aspartyl protease and cytotoxicity. In addition, C. albicans genotype C may be important for pathogenicity in Hokkaido, because the ratio of genotype C was increased in strains derived from oral candidiasis patients.

Microenvironment Responsive Modulations in the Fatty Acid Content, Cell Surface Hydrophobicity, and Adhesion of Candida albicans Cells

Considering the significance in survival and virulence, we have made an attempt to understand modulations in the membrane and cell wall properties of Candida albicans hyphae induced by temperature (37 °C) and neutral pH and yeast form cells grown under low hydrostatic pressure (LHP). Our results suggest that cell surface hydrophobicity (CSH) and adhesion are dynamic properties determined largely by the microenvironment rather than morphological forms, citing the significance of variation in niche specific virulence. GC-MS analysis showed that 49 and 41 fatty acids modulated under hyphal form induced by temperature alone (37 °C) and neutral pH, respectively while that of 58 under yeast form cells under low hydrostatic pressure (LHP) (1800 Pa). Fatty acid and ergosterol data indicates that fluidity increases with increase in temperature (37 °C) and neutral pH i.e., saturated fatty acids and ergosterol decreases. Similarly, CSH and adhesion decrease in response to temperature (37 °C), pH 7, and LHP compared to controls, irrespective of morphological forms. In general, membranes were more rigid, and cell walls were more hydrophobic and adhesive in yeast form compared to hyphal form cells, except in case of yeast form cells grown under LHP. Yeast form cells grown under LHP are less hydrophobic and adhesive.

Adhesion, biofilm formation, cell surface hydrophobicity, and antifungal planktonic susceptibility: relationship among Candida spp

We have performed the characterization of the adhesion profile, biofilm formation, cell surface hydrophobicity (CSH) and antifungal susceptibility of 184 Candida clinical isolates obtained from different human reservoirs. Adhesion was quantified using a flow cytometric assay and biofilm formation was evaluated using two methodologies: XTT and crystal violet assay. CSH was quantified with the microbial adhesion to hydrocarbons test while planktonic susceptibility was assessed accordingly the CLSI protocol for yeast M27-A3 S4. Yeast cells of non-albicans species exhibit increased ability to adhere and form biofilm. However, the correlation between adhesion and biofilm formation varied according to species and also with the methodology used for biofilm assessment. No association was found between strain's site of isolation or planktonic antifungal susceptibility and adhesion or biofilm formation. Finally CSH seemed to be a good predictor for biofilm formation but not for adhesion. Despite the marked variability registered intra and inter species, C. tropicalis and C. parapsilosis were the species exhibiting high adhesion profile. C. tropicalis, C. guilliermondii, and C. krusei revealed higher biofilm formation values in terms of biomass. C. parapsilosis was the species with lower biofilm metabolic activity.

Comparative adherence of Candida albicans and Candida dubliniensis to human buccal epithelial cells and extracellular matrix proteins

Candida albicans and Candida dubliniensis are very closely related pathogenic yeast species. Despite their close relationship, C. albicans is a far more successful colonizer and pathogen of humans. The purpose of this study was to determine if the disparity in the virulence of the two species is attributed to differences in their ability to adhere to human buccal epithelial cells (BECs) and/or extracellular matrix proteins. When grown overnight at 30°C in yeast extract peptone dextrose, genotype 1 C. dubliniensis isolates were found to be significantly more adherent to human BECs than C. albicans or C. dubliniensis genotypes 2-4 (P < 0.001). However, when the yeast cells were grown at 37°C, no significant difference between the adhesion of C. dubliniensis genotype 1 and C. albicans to human BECs was observed, and C. dubliniensis genotype 1 and C. albicans adhered to BECs in significantly greater numbers than the other C. dubliniensis genotypes (P < 0.001). Using surface plasmon resonance analysis, C. dubliniensis isolates were found to adhere in significantly greater numbers than C. albicans to type I and IV collagen, fibronectin, laminin, vitronectin, and proline-rich peptides. These data suggest that C. albicans is not more adherent to epithelial cells or matrix proteins than C. dubliniensis and therefore other factors must contribute to the greater levels of virulence exhibited by C. albicans.

Cell surface hydrophobicity and adhesion: a study on fifty clinical isolates of Candida albicans

Cell surface hydrophobicity (CSH) of 50 clinical isolates of Candida albicans was studied, and values varied broadly in the range 2% to 41%. Purpose of the present work was to investigate correlation of CSH with the C. albicans adherence to solid surfaces, if any. To elucidate this, adhesion to the polystyrene model surface was studied for all the clinical isolates. Adherence varied in the range of 79 to 478 cells per microscopic field. Results indicated no correlation between CSH of the clinical isolates and their adhesion to polystyrene.

A novel allele of HWP1, isolated from a clinical strain of Candida albicans with defective hyphal growth and biofilm formation, has deletions of Gln/Pro and Ser/Thr repeats involved in cellular adhesion

Gene HWP1 encodes a major Candida albicans hyphae cell wall protein which is a substrate of mammalian transglutaminases, promoting the cross-link of the fungus to epithelial cells. Here, we describe a novel HWP1 allele, isolated from C. albicans blood isolates. Analysis of the translated sequence shows that three important regions are absent in the novel allele, HWP1-2, relative to the previously described allele, HWP1-1. Regions 1 and 2 consist of 10 amino acid repeats important for functional conformation of peptide chains and attachment of C. albicans cells to the mammalian epithelia. Region 3 consists of 34 amino acid residues rich in threonine and serine, with O-glycosylation sites that promote the cross-linking with other proteins on C. albicans surface. The HWP1-2 homozygous strain L757 and the heterozygous strain L296 (HWP1-1/HWP1-2) have significantly lower levels of HWP1 expression during hyphal growth and biofilm formation compared to strain SC5314 (HWP1-1/HWP1-1). However, strain L296 properly forms hyphae and biofilms in vitro while strain L757 has reduced hyphal growth (40.4%) and biofilm formation (90.8%). Our results indicate that the HWP1 locus has biofilm specific allelic differential expression and suggest that the HWP1-2 encoded protein is less efficient to maintain cell-to-cell and cell-to-surface adhesion during biofilm formation. This is the first report of a natural variant of HWP1.

The effect of Dodonaea viscosa var. angustifolia on Candida albicans proteinase and phospholipase production and adherence to oral epithelial cells

AIM OF THE STUDY

This study investigated effect of a crude extract of Dodonaea viscosa on the proteinase and phospholipase production and adherence to epithelial cells by Candida albicans isolated from HIV positive and HIV negative patients.

MATERIALS AND METHODS

Twenty Candida albicans strains isolated from HIV positive and 20 from HIV negative patients were investigated. The isolates were exposed to subinhibitory concentration of crude plant extract and adherence, proteinase and phospholipase production were assessed. The results were analysed using Student's t-test and a two-way ANOVA.

RESULTS

Dodonaea viscosa var. angustifolia inhibited the adherence of Candida albicans to oral epithelial cells (p=<0.01) but no significant effect of the plant extract on proteinase and phospholipase production was observed. Results from Candida albicans strains isolated from HIV positive and HIV negative patients were similar.

CONCLUSIONS

Dodonaea viscosa var. angustifolia inhibited the adherence of Candida albicans to oral epithelial cells, which is the initial step of colonization in the infection process. This plant has a therapeutic potential at subinhibitory concentration.

Modification of adherence to plastic and to human buccal cells of Candida albicans and Candida dubliniensis by a subinhibitory concentration of itraconazole

Exposure to subinhibitory concentrations of antifungal agents can influence the adherence of Candida spp. to the host cell. In this study the adherence of Candida albicans ATCC 10231 and Candida dubliniensis CECT 11455 to plastic and to human buccal epithelial cells was evaluated following pre-exposure to 0.5 x minimum inhibitory capacity (MIC) of itraconazole and compared with the corresponding cellular surface hydrophobicity. The yeasts were grown in Sabouraud broth or RPMI-1640 with itraconazole (0.5 x MIC) for 24-26 h at 37 degrees C and the drug was then removed. The adhesion capacity to plastic was studied by turbidimetry in a polystyrene microtiter plate. The adhesion of the yeast to buccal epithelial cells was determined using microscopy techniques. The cellular surface hydrophobicity levels were determined by the microbial adhesion hydrocarbons test. Pre-exposure to itraconazole decreased plastic adherence and cellular surface hydrophobicity in both species when grown in RPMI. When C. albicans was grown in Sabouraud broth, it was nonhydrophobic and did not adhere and therefore no change was detected with the antibiotic. Itraconazole increased adherence to buccal epithelial cells in both species and media studied, as compared to controls without antifungal agents. To study the effects of these antifungal agents on pathogenicity mechanisms, it will be necessary to standardize the methodology for evaluation to determine their in vivo therapeutic efficacy.

Current trends of HIV disease of the mouth

HIV infection affects residents of all countries of the world, but the greater majority of affected individuals reside in the developing world. In the past decade there have been substantial changes in the management of HIV disease, particularly the introduction of highly active antiretroviral therapy (HAART). Such agents have reduced significantly the morbidity and mortality associated with HIV disease, however, they are not available for most HIV-infected individuals in the developing world. There is now considerable understanding of the molecular epidemiology, transmission and therapy of the common opportunistic oral infections of HIV disease, and as a consequence of improved anti-HIV strategies, the frequency and severity of oral disease associated with HIV infection have reduced considerably, although HAART may predispose to human papilloma virus infection of the mouth and potentially increase the risk of later oral squamous cell carcinoma. Despite advances in clinical care the majority of individuals with HIV disease worldwide will continue to develop oral disease, as they are resident in the developing world and do not have ready access to even simple therapies.