Voriconazole -- better chances for patients with invasive mycoses

The past two decades have witnessed an increase in serious fungal infections, without corresponding growth in available antifungal agents. Voriconazole (VRC) is a novel triazole antifungal, recently approved in Europe for treatment of serious infections caused by Aspergillus, Fusarium, Scedosporium, and resistant Candida species. Voriconazole has in vitro activity against yeasts and yeast-like fungi similar, or superior to, fluconazole (FLC), itraconazole (ITC) and amphotericin B (AMB). Candida albicans is generally the most susceptible yeast (VRC MIC subset90 of 0.06 microg/ml); C. krusei often has low MICs even in the face of FLU/ITC resistance. Voriconazole has demonstrated comparable, or better, in vitro activity than ITC and AMB against Aspergillus (mean MICs 0.19-0.58 microg/ml), Ascomycetes, Bipolaris, Fusarium, Blastomyces dermatitidis, Coccidioides immitis, dermatophytes, Histoplasma capsulatum, Malassezia, and Scedosporium angiospermum (P. boydii). The drug possesses potent fungicidal activity against moulds including Aspergillus, Scedosporium, and Fusarium. Fungicidal activity is likely due to the high affinity of VRC for fungal 14-alpha-demethylase, a concept supported by ultrastructural and biochemical analysis. Animal studies confirmed the activity of VRC against infections including pulmonary and invasive aspergillosis (IA); A. fumigatus endocarditis; fusariosis; pulmonary cryptococcosis; and invasive candidiasis. Most importantly, well-designed human clinical trials have confirmed the efficacy of VRC in the treatment of candidal esophagitis, IA, and febrile neutropenia. Smaller studies and case reports have shown VRC is useful for salvage therapy of IA, cerebral aspergillosis, Scedosporium, and other fungal infections. Clinical testing has shown VRC is safe and well tolerated; the most common side effect is benign, self-limited visual disturbance.

Catheter-related candidemia caused by Candida lipolytica in a patient receiving allogeneic bone marrow transplantation

Candida lipolytica was recovered from the blood and the central venous catheter in a patient receiving allogeneic bone marrow transplantation. Two C. lipolytica strains from different geographical areas and the ATCC 9773 strain of C. lipolytica were used as controls. C. lipolytica was identified by standard methods. MICs indicated antifungal susceptibilities to amphotericin B, fluconazole, and itraconazole for all strains. In vitro testing and scanning electron microscopy showed that C. lipolytica was capable of producing large amounts of viscid slime material in glucose-containing solution, likely responsible for the ability of the yeast to adhere to catheter surfaces. Restriction fragment length polymorphisms revealed an identical profile for all clinical isolates, unrelated to those observed for the control strains. This finding suggested the absence of microevolutionary changes in the population of the infecting strain, despite the length of the sepsis and the potential selective pressure of amphotericin B, which had been administered to the patient for about 20 days. The genomic differences that emerged between the isolates and the control strains were indicative of a certain degree of genetic diversity between C. lipolytica isolates from different geographical areas.

Candida attachment to oral epithelium

Inflamed oral mucosa biopsies from patients with thrush and high candidal density were observed in a transmission electron microscope (TEM) using ultra-histochemical staining with ruthenium red for glycocalyx visualization. Fimbriae comprising the glycocalyx and enabling yeast adhesion to epithelial cells were clearly visualized by ruthenium red. All internalized portions of the yeast walls were devoid of glycocalyx, indicating that the growing tips of the hyphae mechanically penetrated the host cells. The attachment of Candida occurred in two ways: by fimbria-mediated adhesion enabling colonization of the epithelial surface, and by invasion of the superficial epithelial cells via hyphae. As the interaction between adhesin receptors and adhesins stimulates the production of proinflammatory cytokines, Candida adhesion itself is assumed to induce mucosal inflammation.

Physiological difference during ethanol fermentation between calcium alginate-immobilized Candida tropicalis and Saccharomyces cerevisiae

Calcium alginate-immobilized Candida tropicalis and Saccharomyces cerevisiae are compared for glucose fermentation. Immobilized C. tropicalis cells showed a slight morphological alteration during ethanol production at 40 degrees C, but their fermentation capacity was reduced by 25%. Under immobilization conditions, the two species demonstrated two different mathematical patterns when the relationship between growth rate, respiration rate, and ethanol tolerance was assessed. The interspecific difference in behavior of immobilized yeast cells is mainly due to their natural metabolic preference. The production of CO(2) by calcium alginate-immobilized C. tropicalis, as well as the lower supply of oxygen to the cells, are the major factors that reduce ethanol production.

Peroxisomal catalase in the methylotrophic yeast Candida boidinii: transport efficiency and metabolic significance

In this study we cloned CTA1, the gene encoding peroxisomal catalase, from the methylotrophic yeast Candida boidinii and studied targeting of the gene product, Cta1p, into peroxisomes by using green fluorescent protein (GFP) fusion proteins. A strain from which CTA1 was deleted (cta1Delta strain) showed marked growth inhibition when it was grown on the peroxisome-inducing carbon sources methanol, oleate, and D-alanine, indicating that peroxisomal catalase plays an important nonspecific role in peroxisomal metabolism. Cta1p carries a peroxisomal targeting signal type 1 (PTS1) motif, -NKF, in its carboxyl terminus. Using GFP fusion proteins, we found that (i) Cta1p is transported to peroxisomes via its PTS1 motif, -NKF; (ii) peroxisomal localization is necessary for Cta1p to function physiologically; and (iii) Cta1p is bimodally distributed between the cytosol and peroxisomes in methanol-grown cells but is localized exclusively in peroxisomes in oleate- and D-alanine-grown cells. In contrast, the fusion protein GFP-AKL (GFP fused to another typical PTS1 sequence, -AKL), in the context of CbPmp20 and D-amino acid oxidase, was found to localize exclusively in peroxisomes. A yeast two-hybrid system analysis suggested that the low transport efficiency of the -NKF sequence is due to a level of interaction between the -NKF sequence and the PTS1 receptor that is lower than the level of interaction with the AKL sequence. Furthermore, GFP-Cta1pDeltankf coexpressed with Cta1p was successfully localized in peroxisomes, suggesting that the oligomer was formed prior to peroxisome import and that it is not necessary for all four subunits to possess a PTS motif. Since the main physiological function of catalase is degradation of H2O2, suboptimal efficiency of catalase import may confer an evolutionary advantage. We suggest that the PTS1 sequence, which is found in peroxisomal catalases, has evolved in such a way as to give a higher priority for peroxisomal transport to peroxisomal enzymes other than to catalases (e.g., oxidases), which require a higher level of peroxisomal transport efficiency.

Bioconversion of nitriles by Candida guilliermondii CCT 7207 cells immobilized in barium alginate

Nitrile degradation by Candida guilliermondii CCT 7207 using free and immobilized cell systems was compared. Different specific growth rates were observed for immobilized (mumax=0.021 h(-1)) and the free cells (mumax=0.029 h(-1)). The maximum specific rate of acetic acid formation was 0.387 h(-1) and 0.266 h(-1) for free and immobilized cells, respectively. Cell adhesion to the support materials was confirmed by scanning electron microscopy. When immobilized, the yeast was able to use high nitrile and amide concentrations (aliphatic and aromatic) as nitrogen sources. The results suggest that C. guilliermondii CCT 7207 presents a physiological pattern potentially useful for the bioremediation of polluted environments or for the bioproduction of amides and organic acid of high commercial value.

Candida tropicalis Etr1p and Saccharomyces cerevisiae Ybr026p (Mrf1'p), 2-enoyl thioester reductases essential for mitochondrial respiratory competence

We report here on the identification and characterization of novel 2-enoyl thioester reductases of fatty acid metabolism, Etr1p from Candida tropicalis and its homolog Ybr026p (Mrf1'p) from Saccharomyces cerevisiae. Overexpression of these proteins in S. cerevisiae led to the development of significantly enlarged mitochondria, whereas deletion of the S. cerevisiae YBR026c gene resulted in rudimentary mitochondria with decreased contents of cytochromes and a respiration-deficient phenotype. Immunolocalization and in vivo targeting experiments showed these proteins to be predominantly mitochondrial. Mitochondrial targeting was essential for complementation of the mutant phenotype, since targeting of the reductases to other subcellular locations failed to reestablish respiratory growth. The mutant phenotype was also complemented by a mitochondrially targeted FabI protein from Escherichia coli. FabI represents a nonhomologous 2-enoyl-acyl carrier protein reductase that participates in the last step of the type II fatty acid synthesis. This indicated that 2-enoyl thioester reductase activity was critical for the mitochondrial function. We conclude that Etr1p and Ybr026p are novel 2-enoyl thioester reductases required for respiration and the maintenance of the mitochondrial compartment, putatively acting in mitochondrial synthesis of fatty acids.

Does metal coating improve the durability of silicone voice prostheses?

Voice prostheses, which are used for voice rehabilitation in cancer patients after laryngectomy, usually become colonized with a mixed biofilm of bacteria and Candida after 2-4 months and lose their efficiency. It is essential to ensure the stability and biocompatibility of these implants. With the aid of surface frame analysis we have shown that local antifungal treatment is inadequate for eliminating the deep infiltration and encapsulation of Candida colonies in silicone. A surface that prevents the adhesion of microorganisms is required. Because of its special properties there are few methods available for coating silicone. We employed, for the first time, a new method of surface modification using anodic vacuum arc coating. Using this method it was possible to obtain a solid film of gold or titanium metal with a layer thickness < 100 nm. Resistance against Candida colonization and destruction of coated prostheses were tested both in vitro and in vivo. A titanium coating seemed to provide the optimal solution to the problem, because surface adhesion and the smoothness of the material appeared to be superior to those of a gold coating.

Genetic evaluation of peroxisomal and cytosolic acetoacetyl-CoA thiolase isozymes in n-alkane-assimilating diploid yeast, Candida tropicalis

The n-alkane-assimilating diploid yeast, Candida tropicalis, possesses two acetoacetyl-CoA thiolase (Thiolase I) isozymes encoded by one allele: peroxisomal and cytosolic Thiolase Is encoded by both CT-T1A and CT-T1B. To clarify the function of peroxisomal and cytosolic Thiolase Is, the site-directed mutation leading Thiolase I delta C6 without a putative C-terminal peroxisomal targeting signal was introduced on CT-T1A locus in the ct-t1b delta-null mutant. The C-terminus-truncated Thiolase I was active and solely present in the cytosol. Although the ct-t1a delta/t1b delta-null mutants showed mevalonate auxotrophy, the mutants having the C-terminus-truncated Thiolase I did not require mevalonate for growth, as did the strains having cytosolic Thiolase I. These results demonstrate that the presence of Thiolase I in the cytoplasm is indispensable for the sterol synthesis in this yeast. It is of greater interest that peroxisomal and cytosolic Thiolase I isozymes, products of the same genes, play different roles in the respective compartments, although further investigations will be necessary to analyze how to be sorted into peroxisomes and the cytosol.

Limitations in the use of ozone to disinfect maple sap

The sap of the maple sugar tree (Acer saccharum) contains 2 to 3% sucrose and is traditionally collected early in the year and concentrated by boiling to produce maple syrup. High levels of microorganisms in the sap occur during holding, leading to a darker syrup with lower economic value. We investigated the use of dissolved ozone as a method to reduce the microbial population in sap. After 40 min of ozone treatment, concentrations of up to 0.30 mg/liter were achieved but were ineffective in reducing the aerobic plate count. Three predominant colonies on nutrient agar were selected for isolation and identification from sap. These included one mucoid and one nonmucoid yeast, both identified as Candida, and Pseudomonas fluorescens. When suspended in buffer, each was readily inactivated by ozone. Addition of 3% sucrose to the buffer markedly reduced the effectiveness of ozone. With the use of an ozone generator with a larger ozone output, saturating ozone concentrations (1 mg/liter) were achieved within 5 min but were accompanied by only a 1-log reduction in aerobic plate count of maple sap. After 40 min of ozone treatment, a less than 3-log reduction occurred. The results indicate that, because of the presence of sucrose, ozone may be of limited use in reducing the microbial population in sap.

In-vivo selection of an azole-resistant petite mutant of Candida glabrata

Two isolates of Candida glabrata from the same stool sample from a bone marrow transplant recipient treated with fluconazole, and designated 1084-L for large colonies on yeast extract-peptone-dextrose-agar and 1084-S for small colonies, were analysed. In-vitro susceptibility tests with a commercially available disk diffusion procedure showed that isolate 1084-L had a susceptibility pattern typical of wild-type strains of C. glabrata with sensitivity to polyenes and the presence of resistant colonies randomly distributed within the inhibition zones for all azole compounds except tioconazole. In contrast, isolate 1084-S, which was found by pulsed-field gel electrophoresis and random amplification of polymorphic DNA to be genetically closely related to isolate 1084-L, exhibited cross-resistance to the azole compounds except tioconazole. Determination of MICs by the E-test method confirmed these results, showing that isolate 1084-S had greater sensitivity to amphotericin B and complete resistance to ketoconazole and fluconazole. Growth on agar plates containing glucose or glycerol as the sole carbon source suggested that the resistant isolate had a respiratory deficiency, which was further demonstrated by flow cytometric analysis of the fluorescence of rhodamine 123-stained blastoconidia. Restriction endonuclease analysis of mitochondrial DNA (mtDNA) established the mitochondrial origin of the respiratory deficiency. However, PCR amplification of the mtDNA with primers ML1 and ML6, as well as transmission electron microscopy, suggested a partial deletion of the mtDNA analogous to that described for rho- petite mutants of Saccharomyces cerevisiae. Together, these results provided evidence that the selection of azole-resistant petite mutants of C. glabrata may occur in vivo after fluconazole administration, which might explain, therefore, clinical failure of antifungal therapy.

[Ultrastructure and mechanism of separation of macroconidia in Monilia fructigena Pers]

Monilia fructigena macroconidia are characterized by availability of endoplasmic reticulum cisternae which are arranged parallel to one another, and large globules of polyphosphates reserve in vacuoles. During the liberation of macroconidia the following processes occur: plugging of the septal pore by plug, development of second continuous septum, rupture of the outer electron dense layer of cell wall, and strict separation.

Antifungal activity of ibuprofen alone and in combination with fluconazole against Candida species

Ibuprofen, a non-steroidal anti-inflammatory drug, exhibited antimicrobial activity against Candida albicans and non-albicans strains. At 10 mg/ml, ibuprofen showed a rapid cidal activity against exponential growth phase C. albicans, accompanied by rapid and extensive leakage of intracellular K+, permeation to propidium iodide, lysis of spheroplasts and severe membrane ultrastructural alterations. These results indicate that the killing of Candida cells is due to direct damage to the cytoplasmic membrane. At 5 mg/ml, ibuprofen inhibited growth; however, it did not kill the yeasts and did not directly affect the cytoplasmic membrane. Evaluation of yeast metabolic vitality with the fluorescent probe FUN-1 showed that growth inhibition induced by the fungistatic drug concentration was due to metabolic alterations. The combination of ibuprofen with fluconazole resulted in synergic activity with eight of the 12 Candida strains studied, including four of the five fluconazole-resistant strains. The MICs of fluconazole for the fluconazole-resistant strains decreased 2-128-fold when the drug was associated with ibuprofen. When in combination with fluconazole, MICs for ibuprofen decreased by up to 64-fold for all the 12 strains studied. These results point to the practicability of using ibuprofen, alone or in combination with azoles, in the treatment of candidosis, particularly when applied topically, taking advantage of the drug's antifungal and anti-inflammatory properties.

Acute conjunctivitis associated with biofilm formation on a punctal plug

BACKGROUND

Punctal plugs are used for the treatment of tear-deficient type dry eye. We recently examined a case of acute conjunctivitis associated with bacterial biofilm formation on a punctal plug.

CASE

A 63-year-old woman diagnosed as having tear-deficient type dry eye came to our hospital with a complaint of soreness in her right eye. Punctal plugs had been inserted into this eye 5 1/2 months previously. On the day of her visit, she presented with acute conjunctivitis.

OBSERVATIONS

In biomicroscopical examination, the top of the punctal plug was seen to be covered with a whitish soft material. Microbiological analysis performed on a part of this material was positive for Staphylococcus haemolyticus and Candida tropicalis. Scanning electron microscopy of the removed punctal plug revealed widespread bacterial colonization embedded within an extensive extracellular matrix. Treatment consisted of the replacement of the plug, and administration of a combination of antibacterial eyedrops and preservative-free artificial solution. As a result, the acute conjunctivitis cleared up within 1 month.

CONCLUSIONS

This case suggests that a punctal plug poses a potential risk of causing the formation of bacterial biofilm. In such a case, replacement of the plug and/or removal of the accumulated materials should be considered.

Candida glabrata displays pseudohyphal growth

The ability to undergo morphological change has been reported as an advantageous trait in fungal pathogenesis. Here we demonstrate that Candida glabrata ATCC2001, like diploid Saccharomyces cerevisiae strains, forms elongated chains of pseudohyphal cells on solid nitrogen starvation media (SLAD). Constrictions were apparent between adjoining cells; no parallel-sided hyphae were seen and pseudohyphae invaded the agar. When SLAD was supplemented with ammonium sulfate both C. glabrata and diploid S. cerevisiae strains lost their ability to undergo pseudohyphal growth. However, on this media C. glabrata yeast cells invaded the agar in a similar fashion to the invasive growth mode exhibited by haploid strains of S. cerevisiae cultured on rich media such as YPD. C. glabrata was not capable of invading YPD demonstrating that the process of filamentation is distinct in these two fungi. To our knowledge this is the first report to demonstrate that C. glabrata can undergo morphological change and grow as an invasive filamentous organism.

Spontaneous candida mediastinitis diagnosed by endoscopic ultrasound-guided, fine-needle aspiration

Candida mediastinitis is a rare clinical entity associated with high mortality and morbidity. It is emerging as an important clinical entity, probably due to increased recognition of candida as a significant pathogen in mediastinitis. Candida mediastinitis is usually associated with cardiothoracic surgery, esophageal perforation, and head and neck infections. Optimal therapy for candida mediastinitis remains undefined. Aggressive, combined surgical debridement and antifungal therapy appears to be the most effective of available therapies. We report a case of spontaneous candida mediastinitis diagnosed by endoscopic ultrasound-guided, fine-needle aspiration and successfully treated with oral antifungal therapy alone.

Peroxisomal membrane protein Pmp47 is essential in the metabolism of middle-chain fatty acid in yeast peroxisomes and Is associated with peroxisome proliferation

Pmp47 of the methylotrophic yeast Candida boidinii belongs to a mitochondrial family of solute transporters and is localized in peroxisomal membranes. Its human homolog, Pmp34, is also known. In this study, we characterized the role of Pmp47 in fatty acid metabolism and peroxisome proliferation using the PMP47-deleted strain of C. boidinii (strain pmp47Delta). The wild-type strain grew well on a middle-chain fatty acid, laureate, as the single carbon source, and mild peroxisome proliferation was observed during its growth. The pmp47Delta strain could not grow on laureate but could grow on long-chain fatty acids including palmitate, myristate, and oleate. The levels of laureate oxidation activity in intact cells and in semi-permeabilized cells of strain pmp47Delta were lower than the respective level in the wild-type strain, although the level of laureate oxidation activity in the cell lysate and the level of lauroyl-CoA oxidation in semi-permeabilized cells of strain pmp47Delta were indistinguishable from the respective level in the wild-type strain. When lauroyl-CoA was provided in the cytosol of strain pmp47Delta through expression of Saccharomyces cerevisiae Faa2p (lauroyl-CoA synthetase) in which its peroxisome targeting signal was deleted, the growth of strain pmp47Delta on laureate was recovered to the level of growth of the wild-type strain. Laureate is converted to its CoA form in peroxisomes by the action of lauroyl-CoA synthetase. These results suggested that Pmp47 is involved in the transport of a small molecule (possibly ATP) required in the conversion of laureate to its CoA form in peroxisomes and that the absence of Pmp47 causes impairment of laureate metabolism, which results in the inability of pmp47Delta cells to grow on laureate. In addition, Pmp47 may be involved in peroxisome proliferation, because the pmp47Delta strain contained a reduced number of peroxisomes, as judged from the fluorescence analysis of cells expressing green fluorescent protein tagged with the peroxisome targeting signal 1 (GFP-AKL).

The isolation and classification of Candida mokoenaii sp. nov. A new yeast isolate from South African soil

A new xylanase producing yeast species was isolated from South African soil. A description of the new species, Candida mokoenaii is given.

Antifungal activity of local anesthetics against Candida species

OBJECTIVE

To evaluate the activity of benzydamine, lidocaine, and bupivacaine, three drugs with local anesthetic activity, against Candida albicans and non-albicans strains and to clarify their mechanism of activity.

METHODS

The minimal inhibitory concentration (MIC) was determined for 20 Candida strains (18 clinical isolates and two American Type Culture Collection strains). The fungistatic activity was studied with the fluorescent probe FUN-1 and observation under epifluorescence microscopy and flow cytometry. The fungicidal activity of the three drugs was assayed by viability counts. Membrane alterations induced in the yeast cells were evaluated by staining with propidium iodide, by quantitation of intracellular K+ leakage and by transmission electron microscopy of intact yeast cells and prepared spheroplasts.

RESULTS

The MIC ranged from 12.5-50.0 microg/mL, 5.0-40.0 mg/mL, and 2.5-10.0 mg/mL for benzydamine, lidocaine, and bupivacaine, respectively. The inhibitory activity of these concentrations could be detected with the fluorescent probe FUN-1 after incubation for 60 minutes. A very fast fungicidal activity was shown by 0.2, 50, and 30 mg/mL of benzydamine, lidocaine, and bupivacaine, respectively.

CONCLUSIONS

At lower concentrations, the tested drugs have a fungistatic activity, due to yeast metabolic impairment, while at higher concentrations they are fungicidal, due to direct damage to the cytoplasmic membrane.

[Taxonomy and ecology of the genus Candida]

Candida is a heterogeneous genus which contains about a quarter of all yeast species. It includes not only species of uncertain affiliation but also unrelated strains whose phylogenetic relationships have not been resolved. A great variety of CoQ types are present in the genus, the mol % G + C ranges from 30-63%, and species that were found to sporulate have teleomorphic counterparts in 11 different genera. Candida species are mainly associated with plants, rotting vegetation, with insects which feed on plants or with food. In line with this, 71% of Candida species utilize xylose (wood degradation), 57% of species use cellobiose (cellulose degradation), 29% oxidize aliphatic hydrocarbons (components of plant cuticula), 27% of species degrade starch as a plant storage material, and 7% utilize methanol as a possible metabolite from pectin catabolism. 85% of species require individual vitamins produced mainly in plant materials. 65% of Candida species are not able to grow at temperatures of 37 degrees C. In comparison only relatively few species occur normally in humans and other warm blooded animals. About 16% of type strains and selected strains for comparative purposes (CBS) were isolated from human specimens. Perhaps up to 10% of Candida species may be of medical importance, though this has so far only been clearly demonstrated for less than 5% of currently known species.

[Orointestinal candidiasis with special emphasis on esophageal candidiasis]

Orointestinal mycoses are localized mainly in the oral cavity and in the oesophagus. Candida oesophagitis is not only found in AIDS-patients, also in patients of risk admitted to intensive care units. Upper intestinoscopies were made in 124 patients. Oesophageal candidosis was found in 6 patients, two of them had also Candida plaques in the stomach. The patients of the intensive care unit had an Apache-II-score of 26.7, those with Candida oesophagitis were 29.5. A significant increase in Candida antibodies was observed with 59 of 124 patients (47.6%), including all patients with oesophageal candidosis. Obviously also Candida infections of other localisations must be suspected. There was a correlation between the severity of endoscopic aspects and the invasiveness observed microscopically.

Factors influencing adherence of Candida spp. to host tissues and plastic surfaces

Attachment of Candida spp. to host tissues and plastic surfaces is the first and a crucial step that initiates colonization by yeast cells and subsequent development of disseminated fungal infection. These infections are associated with high degree of morbidity, mortality and extra cost. Modern trends have focused not only on how best to treat but also on how to prevent Candida infections. To achieve this goal, the factors that influence the adherence of Candida spp. to biological and non biological surfaces have been studied. C. albicans adheres at a degree higher than that of the other Candida spp. and C. tropicalis adheres to a lesser extent. This may reflect the higher pathogenicity of C. albicans compared to the other Candida spp. Germinated C. albicans cells adhere to host tissue more readily than do yeast-phase. Sugars play an important role in the adherence of Candida spp. Overall, galactose was found to promote the adherence of Candida spp. to host tissues and plastic surfaces more than any other mono or disaccharide. Amino sugars on the other hand inhibit the adherence of the yeast cells. Divalent ions such as Ca2+ and Mg2+ promote the adherence of Candida spp. more than monovalent ions. Candida spp. express on their surface receptors, which interact with a wide variety of host proteins including fibrinogen, fibronectin, lamanin, and type I and IV collagen thus binding Candida spp. To glycoproteinaceous conditioning film at the blood-polymer interface. Coaggregation of Candida spp. with other bacteria promotes colonization of yeast cells to oral biofilm, host tissues, and to surfaces of the indwelling vascular catheters. These factors form the basis for the interference with the adherence of Candida spp.

Colony morphology of Candida spp. as a guide to species identification

The presence of colony projections, often referred to as "feet," have typically been considered a characteristic of Candida albicans. In the current study that examined the colony morphology of numerous different species of Candida, several clinical isolates of Candida tropicalis and Candida krusei were also noted to produce "feet." The medium and growth conditions under which colony projections were produced by these species were characterized.

Effects of Pycnoporellus fulgens (Fr.) Donk crude extract on Candida glabrata ultrastructure

Among antifungal products of natural origin, Pycnoporellus fulgens (Fr) Donk, is active against pathogenic yeasts. Our study was carried out to observe the ultrastructural modifications produced by P. fulgens crude extract on Candida glabrata. Yeasts were submitted to different concentrations (50, 100, 200, 400 micrograms ml-1) for 72 h under constant stirring at 35 degrees C. Transmission electron microscopy revealed that the extract acted on the cell envelope (cell wall and plasmalemma). Cell divisions were also affected by thickening of the septum (50 micrograms ml-1) and a deficiency in the daughter cell wall texture. The extent of the antifungal effect clearly depended on the extract concentration.

In vitro pharmacodynamic properties of MK-0991 determined by time-kill methods

MK-0991 has demonstrated activity against a variety of fungal pathogens. We evaluated the MIC endpoint for MK-0991 by reading the endpoint using three methods and comparing these results with minimum fungicidal concentrations and electron micrographs. The concentration that resulted in 80% inhibition of fungal growth compared with control, similar to the endpoint for the azole antifungal agents, provided the most consistent results. Additionally, we investigated the time-kill properties of this agent against two isolates each of Candida albicans, Candida glabrata and Candida tropicalis at concentrations ranging from 0.125 x MIC to 16 x MIC. Kill curves were performed using RPMI buffered with morpholine propanesulfonic acid as growth media. Samples were obtained at predetermined time points over 24 h and plated for colony counting. Fungicidal activity was observed with one isolate of C. albicans, two isolates of C. glabrata, and one isolate of C. tropicalis. MK-0991 displayed concentration-dependent activity, which was fungicidal or fungistatic depending on the isolate tested.