Candida tropicalis has emerged as one of the most important Candida species. It has been widely considered the second most virulent Candida species, only preceded by C. albicans. Besides, this species has been recognized as a very strong biofilm producer, surpassing C. albicans in most of the studies. In addition, it produces a wide range of other virulence factors, including: adhesion to buccal epithelial and endothelial cells; the secretion of lytic enzymes, such as proteinases, phospholipases, and hemolysins, bud-to-hyphae transition (also called morphogenesis) and the phenomenon called phenotypic switching. This is a species very closely related to C. albicans and has been easily identified with both phenotypic and molecular methods. In addition, no cryptic sibling species were yet described in the literature, what is contradictory to some other medically important Candida species. C. tropicalis is a clinically relevant species and may be the second or third etiological agent of candidemia, specifically in Latin American countries and Asia. Antifungal resistance to the azoles, polyenes, and echinocandins has already been described. Apart from all these characteristics, C. tropicalis has been considered an osmotolerant microorganism and this ability to survive to high salt concentration may be important for fungal persistence in saline environments. This physiological characteristic makes this species suitable for use in biotechnology processes. Here we describe an update of C. tropicalis, focusing on all these previously mentioned subjects.

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BackgroundCandida albicans is a diploid yeast that in some circumstances may cause oral or oropharyngeal infections. Yeasts virulence factors contribute for both the maintenance of colonizing strains in addition to damage and cause tissue invasion, thus the establishment of infection occurs. The limited arsenal of antifungal drugs for the treatment of candidiasis turn the investigation of natural products mandatory for the discovery of new targets for antifungal drug development. Therefore, tropical countries emerge as important providers of natural products with potential antimicrobial activity. This study aimed to investigate morphogenesis and secretion of hydrolytic enzymes (phospholipase and proteinase) in the presence of the CE of Eugenia uniflora.MethodsThe isolates were tested for their ability to form hyphae in both solid and liquid media under three different conditions: YPD + 20% FBS, Spider medium and GlcNac and the ability to secrete phospholipase and proteinase in the presence of 2000 μg/mL of E. uniflora.ResultsThe CE of E. uniflora inhibited hypha formation in both liquid and solid media tested. It also impaired hydrolytic enzymes production.ConclusionsThis was the first study to describe the interaction of a natural product with the full expression of three different factors in C. albicans. E. uniflora may be an alternative therapeutic for oral candidiasis in the future.

Several studies have been developed regarding human health risks associated with the recreational use of beaches contaminated with domestic sewage. These wastes contain various micro-organisms, including Candida tropicalis. In this context, the objective of this study was to characterize C. tropicalis isolates from the sandy beach of Ponta Negra, Natal, Rio Grande do Norte, Brazil, regarding the expression of in vitro virulence factors, adaptation to osmotic stress and susceptibility to antifungal drugs. We analyzed 62 environmental isolates and observed a great variation among them for the various virulence factors evaluated. In general, environmental isolates were more adherent to human buccal epithelial cells (HBEC) than C. tropicalis ATCC13803 reference strain, and they also showed increased biofilm production. Most of the isolates presented wrinkled phenotypes on Spider medium (34 isolates, 54.8%). The majority of the isolates also showed higher proteinase production than control strains, but low phospholipase activity. In addition, 35 isolates (56.4%) had high hemolytic activity (hemolysis index > 0.55). With regard to C. tropicalis resistance to osmotic stress, 85.4% of the isolates were able to grow in a liquid medium containing 15% sodium chloride. The strains were highly resistant to the azoles tested (fluconazole, voriconazole and itraconazole). Fifteen strains were resistant to the three azoles tested (24.2%). Some strains were also resistant to amphotericin B (14 isolates; 22.6%), while all of them were susceptible for the echinocandins tested, except for a single strain of intermediate susceptibility to micafungin. Our results demonstrate that C. tropicalis isolated from the sand can fully express virulence attributes and showed a high persistence capacity on the coastal environment; in addition of showing high minimal inhibitory concentrations to several antifungal drugs used in current clinical practice, demonstrating that environmental isolates may have pathogenic potential.

Although yeasts belonging to the genus Candida are frequently seen as commensals in the oral cavity, they possess virulence attributes that contribute for pathogenicity. The aims of the present study were to study the prevalence of Candida spp. isolated from the oral cavity of renal transplant recipients and to analyze strains virulence factors. We isolated a total of 70 Candida strains from 111 transplant recipients, and Candida albicans was the most prevalent species (82.86 %). Oral candidiasis was diagnosed in 14.4 % kidney transplant patients, while 11 isolates (15.7 %) corresponded to non-Candida albicans Candida (NCAC) species. C. albicans adhered to a higher extension than NCAC strains. Some isolates of Candida tropicalis were markedly adherent to human buccal epithelial cells and highly biofilm-forming strains. Regarding proteinase activity, Candida orthopsilosis was more proteolytic than Candida metapsilosis. Candida glabrata and Candida dubliniensis showed very low ability to form biofilm on polystyrene microtiter plates. We have demonstrated here diverse peculiarities of different Candida species regarding the ability to express virulence factors. This study will contribute for the understanding of the natural history and pathogenesis of yeasts belonging to the genus Candida in the oral cavity of patients who were submitted to kidney transplant and are under immunosuppressive therapies.

BackgroundCandida albicans is a diploid yeast that in some circumstances may cause oral or oropharyngeal infections. This investigation aimed to study the prevalence of Candida spp. and to analyze the ABC genotypes of 76 clinical isolates of C. albicans obtained from the oral cavity of kidney transplant patients from two distinct geographic regions of Brazil.MethodsWe typed 48 strains with ABC genotyping and Microsatelitte using primer M13 and tested three virulence factors in vitro: phospholipase activity, morphogenesis and the ability to evade from polymorphonuclear neutrophils phagocytosis.ResultsC. albicans was the most prevalent species (86.4%), followed by C. tropicalis (4.5%). C. albicans genotype A was the most prevalent (58 isolates; 76.4%), followed by genotype C (15 isolates; 19.7%) and genotype B (3 isolates; 3.9%). When Microsatellite technique with primer M13 was applied, 80% of the isolates from the South were placed within the same cluster. The majority of Genotype C strains were grouped together within two different clusters. Genotype C was considered more resistant to PMNs attack than genotypes A and B. Strains isolated from the South of Brazil showed also better ability to combat PMNs phagocytosis.ConclusionsWe found a high rate of C. albicans genotype C strains isolated from the oral cavity of this group of patients. This study characterized oral C. albicans strains isolated from kidney transplant recipients and will contribute to a better understanding of the pathogenesis of oral candidiasis.

This study evaluated the influence of the extract of Eugenia uniflora in adhesion to human buccal epithelial cells (HBEC) biofilm formation and cell surface hydrophobicity (CSH) of Candida spp. isolated from the oral cavity of kidney transplant patients. To evaluate virulence attributes in vitro, nine yeasts were grown in the presence and absence of 1000 μg/mL of the extract. Adhesion was quantified using the number of Candida cells adhered to 150 HBEC determined by optical microscope. Biofilm formation was evaluated using two methodologies: XTT (2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) and crystal violet assay, and further analyzed by electronic scan microscopy. CSH was quantified with the microbial adhesion to hydrocarbons test. We could detect that the extract of E. uniflora was able to reduce adhesion to HBEC and CSH for both Candida albicans and non-Candida albicans Candida species. We also observed a statistically significant reduced ability to form biofilms in biofilm-producing strains using both methods of quantification. However, two highly biofilm-producing strains of Candida tropicalis had a very large reduction in biofilm formation. This study reinforces the idea that besides growth inhibition, E. uniflora may interfere with the expression of some virulence factors of Candida spp. and may be possibly applied in the future as a novel antifungal agent.

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