Nosocomial fungal infections: candidemia

Genetic analysis of resistance to infections in mice: A/J meets C57BL/6J

Susceptibility to infectious diseases has long been known to have a genetic component in human populations. This genetic effect is often complex and difficult to study as it is further modified by environmental factors including the disease-causing pathogen itself. The laboratory mouse has proved a useful alternative to implement a genetic approach to study host defenses against infections. Our laboratory has used genetic analysis and positional cloning to characterize single and multi-gene effects regulating inter-strain differences in the susceptibility of A/J and C57BL/6J mice to infection with several bacterial and parasitic pathogens. This has led to the identification of several proteins including Nrampl (Slc11a1), Birc1e, Icsbp, C5a, and others that play critical roles in the antimicrobial defenses of macrophages against intracellular pathogens. The use of AcB/BcA recombinant congenic strains has further facilitated the characterization of single gene effects in complex traits such as susceptibility to malaria. The genetic identification of erythrocyte pyruvate kinase (Pklr) and myeloid pantetheinase enzymes (Vnn1/3) as key regulators of blood-stage parasitemia has suggested that cellular redox potential may be a key biochemical determinant of Plasmodium parasite replication. Expanding these types of studies to additional inbred strains and to emerging stocks of mutagenized mice will undoubtedly continue to unravel the molecular basis of host defense against infections.

Disruption of the Candida albicans ATC1 gene encoding a cell-linked acid trehalase decreases hypha formation and infectivity without affecting resistance to oxidative stress

In Candida albicans, the ATC1 gene, encoding a cell wall-associated acid trehalase, has been considered as a potentially interesting target in the search for new antifungal compounds. A phenotypic characterization of the double disruptant atc1Delta/atc1Delta mutant showed that it was unable to grow on exogenous trehalose as sole carbon source. Unlike actively growing cells from the parental strain (CAI4), the atc1Delta null mutant displayed higher resistance to environmental insults, such as heat shock (42 degrees C) or saline exposure (0.5 M NaCl), and to both mild and severe oxidative stress (5 and 50 mM H(2)O(2)), which are relevant during in vivo infections. Parallel measurements of intracellular trehalose and trehalose-metabolizing enzymes revealed that significant amounts of the disaccharide were stored in response to thermal and oxidative challenge in the two cell types. The antioxidant activities of catalase and glutathione reductase were triggered by moderate oxidative exposure (5 mM H(2)O(2)), whereas superoxide dismutase was inhibited dramatically by H(2)O(2), where a more marked decrease was observed in atc1Delta cells. In turn, the atc1Delta mutant exhibited a decreased capacity of hypha and pseudohypha formation tested in different media. Finally, the homozygous null mutant in a mouse model of systemic candidiasis displayed strongly reduced pathogenicity compared with parental or heterozygous strains. These results suggest not only a novel role for the ATC1 gene in dimorphism and infectivity, but also that an interconnection between stress resistance, dimorphic conversion and virulence in C. albicans may be reconsidered. They also support the hypothesis that Atc1p is not involved in the physiological hydrolysis of endogenous trehalose.

Species distribution and susceptibility to azole antifungals of Candida bloodstream isolates from eight university hospitals in Korea

PURPOSE

The incidence of Candida bloodstream infections (BSI) has increased over the past two decades. The rank order of occurrence and the susceptibility to antifungals of the various Candida species causing BSI are important factors driving the establishment of empirical treatment protocols; however, very limited multi-institutional data are available on Candida bloodstream isolates in Korea.

MATERIALS AND METHODS

We investigated the susceptibility to azole antifungals and species distribution of 143 Candida bloodstream isolates recovered from eight university hospitals over a six-month period. Minimal inhibitory concentrations (MICs) of fluconazole, itraconazole, and voriconazole for each isolate were determined by the broth microdilution method of the Clinical and Laboratory Standards Institute (CLSI).

RESULTS

The Candida species recovered most frequently from the blood cultures was C. albicans (49%), followed by C. parapsilosis (22%), C. tropicalis (14%), and C. glabrata (11%). The MIC ranges for the Candida isolates were 0.125 to 64 microg/mL for fluconazole, 0.03 to 2 microg/mL for itraconazole, and 0.03 to 1 microg/mL for voriconazole. Overall, resistance to fluconazole was found in only 2% of the Candida isolates (3/143), while the dose-dependent susceptibility was found in 6% (8/143). The resistance and dose-dependent susceptibility of itraconazole were found in 4% (6/143) and 14% (20/143) of the isolates, respectively. All bloodstream isolates were susceptible to voriconazole (MIC, < or = 1 microg/mL).

CONCLUSION

Our findings show that C. albicans is the most common cause of Candida-related BSI, followed by C. parapsilosis, and that the rates of resistance to azole antifungals are still low among bloodstream isolates in Korea.

Rapid identification of Candida species in oral rinse solutions by PCR

AIMS

To determine the sensitivity and specificity of a multiplex PCR assay for the contemporary identification of major species involved in oral candidiasis, without extraction and purification of DNA from the samples under investigation; and evaluation of this method in comparison with routine phenotypic culture identification.

METHODS

78 oral rinse solutions were collected. The concentrated oral rinse technique was used for a quantitative and qualitative study. Research and identification of Candida spp, with routine phenotypic culture identification (germ-tube test in serum at 37 degrees C for 3 hours and sugar assimilation strip analysis), were performed. Each sample was analysed with multiplex PCR directly on oral rinse solution. Samples giving discrepant results between routine phenotypic and PCR identification methods were resubcultured on CHROMagar Candida plates. The fungus-specific primers ITS1, ITS2, CA3, and CA4 were used. For the identification of other species (C kefyr, C famata and C dubliniensis), ITS1F, ITS1K, and ITS2D primers were designed.

RESULTS

Multiplex PCR correctly identified all samples, including those with single species, or with mixed species, negative samples and positive samples which appeared to be negative from routine phenotypic methods.

CONCLUSION

This multiplex PCR assay provides a rapid alternative to the conventional culture based technique for the identification and speciation of the most frequently isolated Candida species. The absence of an extraction method made identification of 10 species possible in a few hours.

Candidemia in immunocompromised and immunocompetent critically ill patients: a prospective comparative study

The purpose of this study was to compare the risk factors, clinical manifestations, and outcome of candidemia in immunocompromised (IC) and nonimmunocompromised (NIC) critically ill patients. Data were collected prospectively over a 2-year period (02/2000–01/2002) from patients in a 25-bed, medical–surgical intensive care unit (ICU). Eligible for participation in this study were patients who developed candidemia during their ICU stay. Patients under antifungal therapy and with a confirmed systemic fungal infection prior to the diagnosis of candidemia were excluded. Cultures of blood, urine, and stool were performed for all patients in the study, and all patients underwent endoscopy/biopsy of the esophagus for detection of Candida. Smears and/or scrapings of oropharyngeal and esophageal lesions were examined for hyphae and/or pseudohyphae and were also cultured for yeasts. During the study period, 1,627 patients were hospitalized in the ICU, 57% for primary medical reasons and 43% for surgical reasons. After application of the study’s inclusion and exclusion criteria, 24 patients with candidemia (9 IC and 15 NIC) were analyzed. Total parenteral nutrition was more common in IC than in NIC patients (9/9 [100%] vs 8/15 [53%], p = 0.02). Oropharyngeal candidiasis was detected in 5 of 9 (55.5%) IC patients and in 1 of 15 (6.5%) NIC patients (p = 0.015). Esophageal candidiasis was also more common in IC than in NIC patients (4/9 [44%] vs 0/15 [0%], p = 0.012). Among the 9 IC patients, all except 2 died, resulting in a crude mortality of 78%; among the 15 NIC patients, 9 died, resulting in a crude mortality of 60% (p > 0.05). Autopsy was performed in two IC and in six NIC patients, with disseminated candidiasis found in one IC patient. Oropharyngeal and esophageal candidiasis are frequent in IC patients with candidemia. In contrast, this coexistence is rare in NIC critically ill patients with Candida bloodstream infections. A high mortality was noted in both IC and NIC critically ill patients with candidemia.

Phenolic compounds and antimicrobial activity of olive (Olea europaea L. Cv. Cobrançosa) leaves

We report the determination of phenolic compounds in olive leaves by reversed-phase HPLC/DAD, and the evaluation of their in vitro activity against several microorganisms that may be causal agents of human intestinal and respiratory tract infections, namely gram positive (Bacillus cereus, B. subtilis and Staphylococcus aureus), gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae) and fungi (Candida albicans and Cryptococcus neoformans). Seven phenolic compounds were identified and quantified: caffeic acid, verbascoside, oleuropein, luteolin 7-O-glucoside, rutin, apigenin 7-O-glucoside and luteolin 4'-O-glucoside. At low concentrations olive leaves extracts showed an unusual combined antibacterial and antifungal action, which suggest their great potential as nutraceuticals, particularly as a source of phenolic compounds.

Antifungal susceptibility of 1000 Candida bloodstream isolates to 5 antifungal drugs: results of a multicenter study conducted in São Paulo, Brazil, 1995–2003

We evaluated all Candida sp. bloodstream isolates obtained from patients admitted to 4 tertiary care hospitals between 1995 and 2003 in the city of São Paulo, Brazil. Susceptibility to amphotericin B, 5-fluorocytosine, fluconazole (FCZ), itraconazole (ITZ), and voriconazole (VCZ) was determined using the Clinical Laboratory Standards Institute broth microdilution method. We tested a total of 1000 strains, including 400 strains of Candida albicans (40%), 243 of Candida tropicalis (24.3%), 238 of Candida parapsilosis (23.8%), 44 of C. glabrata (4.4%), 30 of Candida guilliermondii (3%), and 25 of Candida rugosa (2.5%). Only 1.9% of the strains tested were susceptible in a dose-dependent manner, and 0.2% of them were resistant to FCZ. Almost 100% of the strains were susceptible to VCZ. Despite that azole resistance was a rare finding, a trend toward increased resistance among C. rugosa strains to FCZ and ITZ was noted.

Evaluation the anti proliferative activity of structural proteins and fraction of supernatant from culture of Candida albicans

In this study, anti proliferative activity of structural proteins and fraction of supernatant from culture of Candida albicans on proliferation responses of lymph node cells in Balb/c mice have been evaluated. For this reason Candida albicans was cultured in RPMI medium supplemented with 10% FBS at 37 in 5% CO2 until reaching a confluent state for 2 weeks. The culture supernatant was obtained by centrifugation and purified by gel filtration chromatography and structural proteins of C. albicans were obtained from breakage of cell wall by vortexing with glass beads in suspension of PBS and 1 mM PMSF and then cultured with lymph node cells and evaluated by MTT assay. The results in this study demonstrated that both of structural proteins and fraction of supernatant from culture of Candida albicans suppress immune responses compared with Control group. Our study provides evidence that proteins of C. albicans have anti proliferative activity.

Investigation of the possible association between nosocomial candiduria and candidaemia

This study aimed to determine whether candiduria is associated with the occurrence of nosocomial candidaemia. In the case-control part of the study, 115 cases (nosocomial candidaemia) and 115 controls (nosocomial bacteraemia) were similar in age, severity of condition and time of hospitalisation. There was a significant association of candidaemia with candiduria (OR 9.79; 95% CI 2.14-44.76). In the microbiology part of the study, 23 pairs of Candida-positive urine and blood cultures were obtained from 23 patients. In ten (43%) cases, the urine and blood culture isolates belonged to different species, and molecular typing showed a difference in two of the 13 cases yielding the same species from both specimens. Overall, there was a significant association between candiduria and candidaemia, but the Candida isolates from urine and blood were different for 52% of the patients. Thus, the data indicated that the urinary tract was probably not a source for the candidaemia.

The cellular resistance against oxidative stress (H2O2) is independent of neutral trehalase (Ntc1p) activity in Candida albicans

The protective role of trehalose against oxidative stress caused by hydrogen peroxide in Candida albicans has been investigated in the homozygous mutant ntc1Delta/ntc1Delta, disrupted in the NTC1 gene, which encodes the neutral (cytosolic) trehalase (Ntc1p). After a severe oxidative exposure (50 mM H(2)O(2)), both parental (CAI-4) and ntc1Delta/ntc1Delta exponential-phase cells stored large amounts of intracellular trehalose. In turn, the degree of cell survival was roughly equivalent in both strains, although slightly higher in ntc1Delta/ntc1Delta cultures. The mechanism of 'adaptive tolerance' was functional in the two strains. Thus, a gently oxidative pretreatment (5 mM H(2)O(2)) increased the recovery of cellular viability when it was followed by a severe challenge (50 mM H(2)O(2)); this phenomenon was accompanied by a significant elevation of the endogenous trehalose content. Oxidative stress also induced specific activation of the antioxidant enzymes catalase and glutathione reductase upon gentle oxidative treatment (5 mM H(2)O(2)), whereas superoxide dismutase activity was only activated upon prolonged exposure. Taken together, these results strongly suggest that in C. albicans neutral trehalase activity does not play an essential role in the protective response against oxidative stress. They also suggest that a diminished Ntc1p activity might favour the growth of C. albicans cells subjected to a strong oxidative exposure.

Secretion of serine peptidase by a clinical strain of Candida albicans: influence of growth conditions and cleavage of human serum proteins and extracellular matrix components

Candida albicans expresses a vast number of hydrolytic enzymes, playing roles in several phases of yeast-host interactions. Here, we identified two novel extracellular peptidase classes in C. albicans. Using gelatin-sodium dodecyl sulfate polyacrylamide gel electrophoresis two gelatinolytic activities were detected at physiological pH: a 60-kDa metallopeptidase, completely blocked by 1,10-phenanthroline, and a 50-kDa serine peptidase inhibited by phenylmethylsulfonyl fluoride. In an effort to establish a probable functional implication for these novel peptidase classes, we demonstrated that the 50-kDa secretory serine peptidase was active over a broad pH range (5.0-7.2) and was capable to hydrolyze some soluble human serum proteins and extracellular matrix components. Conversely, when this isolate was grown in yeast carbon base supplemented with bovine serum albumin, a secretory aspartyl peptidase activity was measured, instead of metallo- and serine peptidases, suggesting that distinct medium composition induces different expression of released peptidases in C. albicans. Additionally, we showed by quantitative proteolytic measurement, flow cytometry and immunoblotting assays that the brain heart infusion medium might repress the Sap1-3 production. Collectively, our results showed for the first time the capability of an extracellular proteolytic enzyme other than aspartic-type peptidases to cleave a broad spectrum of relevant host proteinaceous substrates by the human pathogen C. albicans.

Nosocomial bloodstream infections associated with Candida species in a Turkish University Hospital

In recent years, a progressive increase in the frequency of nosocomial candidaemia has been observed, especially among the critically ill or immunocompromised patients. The aim of this study was to evaluate the trend in incidence of candidaemia together with potential risk factors in an 850-bed Turkish Tertiary Care Hospital in a 4-year period. A total of 104 candidaemia episodes were identified in 104 patients. The overall incidence was 0.56 per 1000 hospital admissions and the increase in incidence of candidaemia from 2000 to 2003 was found to be statistically significant (P = 0.010). Candida albicans was the most common species (57.7%) and non-albicans species accounted for 42.3% of all episodes. The most common non-albicans Candida sp. isolated was C. tropicalis (20.2%) followed by C. parapsilosis (12.5%). The most frequent risk factors possibly associated with the candidaemia were previous antibiotic treatment (76.9%), presence of central venous catheter (71.2%) and total parenteral nutrition (55.8%). Our results show the fact that the incidence of candidaemia caused by non-albicans species is frequent and increasing significantly, although the most common isolated Candida species were C. albicans and further investigations are necessary to evaluate the mechanisms of increasing incidence of candidaemia caused by non-albicans species.

Differential protein expression of murine macrophages upon interaction with Candida albicans

Numerous studies highlight the importance of macrophages for optimal host protection against systemic Candida albicans infections. We chose the murine macrophage cell line RAW 264.7 and the wild-type strain C. albicans SC5314 to study of the induced expression/repression of proteins in macrophages when they are in contact with C. albicans, based on 2-DE, comparison between different gels and protein identification. RAW 264.7 cells were allowed to interact with C. albicans cells for 45 min, and a significant differential protein expression was observed in these macrophages compared to controls. Gels were stained with SYPRO Ruby, allowing a better quantification of the intensity of the protein spots. Fifteen spots were up-regulated, whereas 32 were down-regulated; 60 spots appeared and 49 disappeared. Among them, we identified 11 proteins: annexin I, LyGDI (GDID4), Hspa5 (Grp78, Bip), tropomyosin 5 and L-plastin, that augment; and Eif3s5, Hsp60, Hspa9a, Grp58 (ER75), and Hspa8a (Hsc70), that decrease. The translation elongation factor (Eef2p) is modified in some of its different protein species. Many processes seem to be affected: cytoskeletal organisation, oxidative responses (superoxide and nitric oxide production) and protein biosynthesis and refolding.

Clonal population structure and genetic diversity of Candida albicans in AIDS patients from Abidjan (Côte d'Ivoire)

We have investigated the genotype at 14 enzyme-encoding loci in 275 isolates of the pathogenic yeast Candida albicans sampled from 42 HIV-positive patients (all but one with AIDS) from Abidjan (Côte d'Ivoire). We separately analyzed the following variables: patient, residence, age, gender, T cell count, hospitalization (yes or no), drug treatment, date of sampling, multilocus genotype, and serotype. The most important factors contributing to the genetic variability of C. albicans are individual patient and gender. Our data manifest that the population size of the parasite is relatively small within each patient, although larger in women than in men, and that, at least for the patients involved in the study, the transmission rate of C. albicans between human adults is very low. Most important is the inference that the prevailing mode of reproduction of C. albicans in natural populations is clonal, so that sexual reproduction is extremely rare, if it occurs at all.

FTIR spectroscopy as a potential tool to analyse structural modifications during morphogenesis of Candida albicans

Candida albicans is a polymorphic organism that grows under certain conditions as blastospores, hyphae or pseudohyphae. The potentials of FTIR spectroscopy for assessing structural differences in C. albicans blastospores and hyphae were investigated. The main observed differences were localised in the polysaccharide (950-1,185 cm(-1)), protein (1,480-1,720 cm(-1)), and the fatty acids (2,840-3,000 cm(-1)) regions. Quantitative evaluation of differences between hyphae and blastospores by curve-fitting of these regions indicate that these modifications could be due to both changes in structure and content of components of the cell wall such as beta-glucans, mannoproteins, and lipids. Furthermore, glycogen consumption could be involved during hyphae elongation. Thus, FTIR spectroscopy can be an interesting tool to investigate differences in structure and in content between blastospores and hyphae. We also demonstrate through this study that differentiation of C. albicans clinical strains using hyphae is feasible, as this has been previously shown with blastospores. This preliminary work on identification of C. albicans using hyphae is a prelude to a larger clinical study for early typing within 7 h from a pure culture.

Cockroaches as carriers of fungi of medical importance

The fungal pathogenic flora of the external surface of 103 cockroaches (Periplaneta americana) collected from the intensive care unit of a hospital were investigated. In this study, a high percentage of test cockroaches (93.2%) were found to carry fungi of medical importance. The main fungi isolated were species of Candida, Aspergillus and Penicillium. Information about the carriage of pathogenic fungi by cockroaches in hospital environment is scanty. The results suggest that cockroaches can play a role in dissemination of fungi, which they can carry on their external surface.

Tin(IV) complexes of pyrrolidinedithiocarbamate: synthesis, characterisation and antifungal activity

The reaction of ammonium pyrrolidinedithiocarbamate, [NH4{S2CN(CH2)4}], with SnCl2, [Sn(C6H5)2Cl2], [Sn(C6H5)3Cl], [Sn(C4H9)2Cl2] and [Sn(C6H11)3Cl] produced in good yield the compounds [Sn{S2CN(CH2)4}2Cl2] (1), [Sn{S2CN(CH2)4}2Ph2] (2), [Sn{S2CN(CH2)4}Ph3] (3), [Sn{S2CN(CH2)4}2 n-Bu2] (4) and [Sn{S2CN(CH2)4}Cy3] (5). The complexes were characterised by infrared, multinuclear NMR (1H, 13C{1H} and 119Sn{1H}) and 119Sn Mössbauer spectroscopies. In addition, the crystal structure of 4 was determined by X-ray crystallography. The in vitro antifungal activity of the tin(IV) complexes as well of the ligand was performed on human pathogenic fungi, Candida albicans, in concentrations of 0.025; 0.050; 0.100; 0.200; 0.400; 0.800; 1.600 and 3.200 mM. The microorganism presented resistance to the dithiocarbamate ligand and all tin(IV) complexes tested were actives. The highest activity was found for compounds 1 and 4.

A retrospective Evaluation of fluconazole for the treatment of Candida glabrata fungemia

BACKGROUND

Candida glabrata accounts for 21% of Candida bloodstream isolates in the United States and ranges from susceptible-dose-dependent to resistant to fluconazole. A fluconazole dose of 800 mg/d ( approximately 12 mg/kg per day) is predicted to produce peak plasma concentrations that surpass the susceptible-dose-dependent MIC breakpoint of 16 to 32 mug/mL. Accordingly, the Infectious Diseases Society of America treatment guidelines for candidiasis recommend fluconazole 12 mg/kg per day as an alternative option for treatment of C glabrata fungemia.

OBJECTIVE

The main objective of this study was to evaluate fluconazole retrospectively as a treatment for C glabrata fungemia.

METHODS

Data were collected through a database that stores patient information electronically and can be accessed and queried, and chart review at Barnes-Jewish Hospital (St. Louis, Missouri) from January 1999 to August 2002. Eligible patients who had at least 1 positive blood culture for C glabrata and received at least 1 dose of fluconazole were identified through the electronic query. Chart reviews of these patients followed. The primary outcomes were fungemia eradication and in-hospital mortality.

RESULTS

Of the total 124 cases of C glabrata fungemia identified, 54 patient charts were evaluable. Chart review revealed that 65% (17/26) of patients receiving fluconazole as the sole antifungal therapy had successful bloodstream eradication of C glabrata, whereas approximately 54% (15/28) of patients who were changed from fluconazole to an amphotericin B formulation had successful bloodstream eradication. Although no association was found between fluconazole dose and fungemia eradication in the entire study population, higher doses of fluconazole (> or =400 mg/d) were more likely to achieve fungemia eradication than lower doses (< or =400 mg/d) in the subset of patients who received only fluconazole (P = 0.042). Mortality rates were approximately 24% (4/17) and 40% (6/15) in patients having successful bloodstream eradication with fluconazole alone and with fluconazole followed by amphotericin B, respectively, compared with 38% (3/8) in patients with persistent fungemia who received fluconazole alone.

CONCLUSIONS

Fluconazole was a viable therapy for C glabrata fungemia, with bloodstream eradication in 65% of patients and mortality rates of 24% to 40% in this retrospective chart review.

Synthesis and X-ray crystal structure of [Ag(phendio)2]ClO4 (phendio = 1,10-phenanthroline-5,6-dione) and its effects on fungal and mammalian cells

The Cu(II) and Ag(I) complexes, [Cu(phendio)3](ClO4)2 x 4H2O and [Ag(phendio)2]ClO4 (phendio = 1,10-phenanthroline-5,6-dione), are prepared in good yield by reacting phendio with the appropriate metal perchlorate salt. The X-ray crystal structure of the Ag(I) complex shows it to have a pseudo tetrahedral structure. 'Metal-free' phendio and the Cu(II) and Ag(I) phendio complexes strongly inhibit the growth of the fungal pathogen Candida albicans, and are more active than their 1,10-phenanthroline analogues. The simple Ag(I) salts, AgCH3CO2, AgNO3 and AgClO4 x H2O display superior anti-fungal properties compared to analogous simple Cu(II) and Mn(II) salts, suggesting that the nature of the metal ion strongly influences activity. Exposing C. albicans to 'metal-free' phendio, simple Ag(I) salts and [Ag(phendio)2]ClO4 causes extensive, non-specific DNA cleavage. 'Metal-free' phendio and [Ag(phendio)2]ClO4 induce gross distortions in fungal cell morphology and there is evidence for disruption of cell division. Both drugs also exhibit high anti-cancer activity when tested against cultured mammalian cells.

In vitro susceptibility of yeasts isolated from patients in intensive care units to fluconazole and amphotericin B during a 3-year period

Fungal infections have increased dramatically in recent years and candidemia is a major risk factor for morbidity and mortality in intensive care units (ICUs). Candidemia has been considered to be a nosocomial infection that is strongly associated with neutropenia, recent surgery or presence of intravascular lines, and previous colonization is an independent risk factor. We evaluated the in vitro efficacy of fluconazole and amphotericin B against yeasts isolated from various clinical specimens of colonized or infected patients treated in the ICUs of the Institute of Cardiology, Istanbul University. A total of 1397 ICU patients were treated at the Institute of Cardiology between January 2000 and December 2002. A total of 117 yeasts isolated from 97 patients were included in this study. These ICU patients were hospitalized for a mean of 29 days. All yeasts were identified by conventional methods and using the API (20C AUX, ID 32C) system (Bio Meriéux, France). Susceptibility to fluconazole and amphotericin B was evaluated using the E-test (AB Biodisk, Solna, Sweden). The most commonly isolated yeast was Candida albicans (72.6%), followed by Candida tropicalis (16.2%), Candida kefyr, Candida krusei, Candida parapsilosis, Trichosporon mucoides and Geotrichum spp. Fluconazole and amphotericin B MIC90 values were 0.75 microg/ml; 0.19 microg/ml and 1 microg/ml; 0.38 microg/ml for C. albicans and C. tropicalis, respectively. All Geotrichum spp. were found to be susceptible-dose dependent (SDD) (MIC=16-32 microg/ml) to fluconazole. Two C. albicans, two C. tropicalis, one C. krusei and one Geotrichum spp. had a MIC value of > or = 0.38 microg/ml for amphotericin B. The rate of colonization was 3.36% (47/1397). Only 10 (0.71%) patients out of a total of 1397 developed candidemia during the period of the investigation. Of these, 7 (70%) were caused by non-albicans Candida spp.

Enhanced killing of Candida albicans by human macrophages adherent to type 1 collagen matrices via induction of phagolysosomal fusion

Candida albicans, a component of the normal flora of the alimentary tract and mucocutaneous membranes, is the leading cause of invasive fungal disease in premature infants, diabetics, and surgical patients and of oropharyngeal disease in AIDS patients. As little is known about the regulation of monocyte/macrophage anti-Candida activity, we sought to determine if fungicidal activity might be regulated by extracellular matrix proteins to which monocytes/macrophages are adherent in vivo. Compared to monocyte/macrophages that adhered to plastic, human monocytes and monocyte-derived macrophages that adhered to type 1 collagen matrices, but not to fibronectin, vitronectin, or laminin, demonstrated a significant increase in candidacidal activity. The enhancement of monocyte fungicidal activity was maintained over a 4-h period, whereas macrophage fungicidal activity was maximum at 1 h. Although adherence of monocytes and macrophages to collagen matrices concomitantly enhanced the production of superoxide anion, only the fungicidal activity of collagen-adherent monocytes was partially blocked by superoxide dismutase and catalase. Remarkably, we found that only 10% of the phagosomes in C. albicans-infected macrophages that adhered to plastic fused with lysosomes. In contrast, 80% of yeast-containing phagosomes of collagen-adherent macrophages fused with lysosomes. These data suggest that nonoxidative mechanisms are critical for human macrophage anti-Candida activity and that C. albicans pathogenicity is mediated, in part, by its ability to inhibit phagolysosomal fusion in macrophages.

Genetic analysis of innate immunity in resistance to Candida albicans

Systemic candidiasis is a significant cause of nosocomial infections and the mechanisms of defense against Candida albicans in humans remain poorly understood. Studies in animal models have demonstrated the importance of innate immunity in controlling the response to infection. Although Th1 cytokines have been shown to direct the overall outcome of infection, the precise role of the Th1/Th2 response and, more generally, the adaptive immune response as a whole, in systemic candidiasis, appears to apply mainly to the development of resistance to reinfection. A genetic approach to the identification of host factors regulating pathogenesis and susceptibility to C. albicans infection has been used in humans and in mouse models of infection. Mouse mutants bearing experimentally induced mutations in specific genes have provided a systematic tool for directly assessing the role of individual proteins in C. albicans susceptibility. Inbred mouse strains have been valuable in showcasing the spectrum of naturally occurring variations in initial susceptibility to infection, and type of disease developed. Crosses between resistant and susceptible strains have led to the detection of additional gene effects affecting innate immunity. Of particular interest is the major effect of a naturally occurring loss-of-function mutation in the C5 complement component that has become fixed in many inbred strains. These and other studies have shown that both a functional complement pathway and robust inflammatory response are critical for resistance to C. albicans.

High frequency of Candida parapsilosis on the hands of healthy hosts

The presence of yeasts on the hands of 86 healthy hosts (62 hospital workers and 24 healthy members of the community with no hospital exposure) was investigated. A high rate of colonization was found (59.3%). Candida parapsilosis was the most frequently isolated species (51%), independent of the origin of the samples. The potential virulence and resistance to antifungals of the 26 C. parapsilosis isolates were determined. All were proteinase producers and formed biofilms. The haemolytic activity was variable, with a predominance of total haemolysis of sheep erythrocytes. All isolates were susceptible to amphotericin B but two showed reduced susceptibility to fluconazole. Healthy people may be colonized by a species of yeast with a high capacity for adhesion to plastic surfaces, providing an infection risk to susceptible individuals.

Induction of apoptosis in yeast and mammalian cells by exposure to 1,10-phenanthroline metal complexes

1,10-Phenanthroline (phen) and metal-phen complexes display fungicidal and fungiststic activity, disrupt mitochondrial function and induce oxidative stress. We have examined the effect of these drugs on the structure of yeast and mammalian cell organelles and the integrity of cellular DNA. Exposure of Candida albicans to [Mn(phen)2(mal)].2H2O or [Ag2(phen)3(mal)].2H2O (mal H2 = malonic acid) resulted in DNA degradation whereas exposure to phen or [Cu(phen)2(mal)].2H2O did not. All drugs induced extensive changes to the internal structure of yeast cells including retraction of the cytoplasm, nuclear fragmentation and disruption of the mitochondrion. In the case of cultured mammalian cells [Cu(phen)2(mal)].2H2O induced apoptosis as evidenced by the ladder pattern of DNA fragments following gel electrophoresis and also the blebbing of the cell membrane. The other drugs produced non-specific DNA degradation in mammalian cells. In conclusion, phen and metal-phen complexes have the potential to induce apoptosis in fungal and mammalian cells. Given their distinct mode of action compared to conventional anti-fungal drugs, phen and metal-phen complexes may represent a novel group of anti-fungal agents for use either in combination with existing drugs or in cases where resistance to conventional drugs has emerged.

Electrophoretic variants of intracellular catalase of different Candida species

Intracellular and extracellular catalases of different species of Candida were investigated using different culture media. All the Candida strains produced intracellular catalase, whose enzymatic activity was detected by non-denaturating polyacrylamide gradient (4-30%) gel electrophoresis. The cell extracts presented a major 230 kDa catalase band and in some strains variants of catalase with different molecular weights were detected. Candida catalase activity was not affected by heating at 50 degrees C and incubation with beta-mercaptoethanol, but treatment with sodium dodecyl sulphate inhibited or reduced enzymatic activity. Extracellular enzyme activity was not detected in any of the culture filtrate extracts tested.

Candidemia in a pediatric intensive care unit

OBJECTIVE

To examine the incidence, epidemiology, and clinical characteristics of candidemia in a pediatric intensive care unit.

DESIGN

Retrospective cohort study.

SETTING

Pediatric intensive care unit of a tertiary care teaching and referral hospital in north India.

SUBJECTS

All patients with candidemia from March 1993 to December 1996.

INTERVENTIONS

Patient-related data were analyzed to study candidemia in relation to reason for fungal culture, underlying medical conditions, predisposing factors, Candida isolates, antimicrobial and antifungal treatment, and deaths.

MEASUREMENTS AND MAIN RESULTS

Sixty-four patients with candidemia were identified. The Candida species isolated were Candida tropicalis (48.4%), C. albicans (29.7%), C. guillermondii (14.1%), C. krusei (6.3%), and C. glabrata (1.6%). Thirty-three patients were detected by a high-risk surveillance blood culture, whereas 31 patients were detected while undergoing septic workup. Sixteen (25%) patients were asymptomatic; they recovered without any antifungal therapy and without any sequelae. Of 48 symptomatic patients, 11 died before institution of antifungal therapy; 37 received oral itraconazole (10 mg.kg(-1).day(-1)). Seven (19%) of these 37 patients died. Those who recovered had sterile culture on average by day 14 (range, 4-30) and received the antifungal therapy on average for 24 days (range, 9-42 days). Overall mortality rate was 28.1%, and bivariate analysis showed significant association with Pediatric Risk of Mortality score (p =.0001), presence of symptoms (p =.003), isolation of nonalbicans Candida in general (p =.04) and C. tropicalis specifically (p =.001), and failure to give presumptive antifungal therapy (p =.055). On multivariate analysis, Pediatric Risk of Mortality score and isolation of C. tropicalis were the only significant predictors of mortality.

CONCLUSIONS

Nonalbicans Candida accounted for 70% of candidemia in a pediatric intensive care unit. High-risk surveillance blood cultures aided diagnosis in about half the patients. Severity of illness and isolation of C. tropicalis were significant predictors of mortality.

Morphotypic and genotypic characterization of sequential Candida parapsilosis isolates from an outbreak in a pediatric intensive care unit

Candidemia outbreaks that due to cross-infection are an emerging problem in hospitals. Typing of microorganisms is an essential tool for understanding the epidemiologic aspects of the infection. Techniques based on phenotypic characteristics are inexpensive and easy to perform but are limited by their lack of reproducibility. This study assessed the value of several phenotypic and genotypic techniques that are used in epidemiologic investigations of Candida parapsilosis in clinical practice and used a combination of these methods to analyze outbreak of C. parapsilosis candidemia. Random amplification of polymorphic DNA polymerase chain reaction with several primers was unsatisfactory because it lacked discriminatory power. By simplifying the reading of the morphotypes, we increased their reproducibility for each malt agar and 2,3,5-triphenyltetrazolium media (97% and 90%) and thus their suitability for its use. The combination of electrophoretic karyotype and the simplified morphotypes was rapid and practical to characterize the different clusters involved in the intensive care unit outbreak.

Leucinostatin-A loaded nanospheres: characterization and in vivo toxicity and efficacy evaluation

Leucinostatin A (Leu-A) is a nonapeptide exerting a remarkable activity especially against Candida albicans and Cryptococcus neoformans; nevertheless, its employment is limited due its toxicity. Therefore, we recently developed liposomal formulations, as suitable delivery systems, in order to increase its therapeutic index. However, liposomes present disadvantages related to their long-term instability. For this reason poly(lactic-co-glycolic) nanospheres (NS) were chosen as alternative colloidal carriers for Leu-A delivery. NS were formulated by spontaneous emulsification solvent diffusion method. This study investigates the effects of different parameters on drug encapsulation efficiency and particle size as well. The best preparation obtained was also characterized for its in vitro release, in vivo acute toxicity (LD50), and effectiveness against C. albicans in mice. In vitro release was performed over 100 h and resulted sufficiently sustained with more than 93% of the peptide released. Acute toxicity showed that the LD50 was increased more than 18-fold and the study on systemic candidiasis models revealed high effectiveness of the NS in reducing either the growth of fungal colonies in infected mice liver or in the mortality index. In conclusion, we can propose that Leu-A loaded NS could represent a new promising therapeutic system against Candida infection.

Distribution and antifungal susceptibility of Candida species causing candidemia from 1996 to 1999

Susceptibilities to amphotericin B and fluconazole of 383 Candida species isolated from blood were determined. Candida albicans was the most common species (55.6%), followed by Candida parapsilosis (17.5%), Candida tropicalis (16.5%), Candida glabrata (5.2%), Candida guilliermondii (2.3%), and others (2.9%). All but three isolates, Candida ciferrii, C. tropicalis, and C. glabrata, one each, were susceptible to amphotericin B. A total of 367 (95.8%) and 15 (4.2%) isolates were susceptible and susceptible-dose dependent to fluconazole, respectively. Only one isolate, a C. glabrata, was resistant to fluconazole. Few patients (13%) having prior fluconazole treatments may explain the low rate of resistance to fluconazole in this study.

Circulating beta (1-3) glucan and immunoglobulin G subclass antibodies to Candida albicans cell wall antigens in patients with systemic candidiasis

Invasive candidiasis in patients who are immunocompromised or in intensive care units (ICUs) presents both diagnostic and therapeutic problems. We previously described antibodies that were directed against Candida albicans cell wall fragments (CW), periodate-treated CW (CW(IO4)), phosphopeptidomannan (PPM), and beta(1-3) glucan. In this study, circulating fungal antigens [mannan and beta(1-3) glucan] and immunoglobulin G (IgG) subclass antibodies to these cell wall antigens (anti-CW) were analyzed in patients with systemic candidiasis. Sera were collected from 14 patients on two or three consecutive occasions, starting on the day when candidiasis was culture proven. The sera were analyzed by enzyme-linked immunosorbent assay. The control groups consisted of lactating mothers (n = 9) (group I) who had breast milk that was positive for C. albicans and also had acute inflammation of the nipples, and age-matched blood donors (n = 10) (group II). Within the first 3 weeks of Candida infection all of the patients were positive for beta(1-3) glucan by the Gluspecy test, but no patients were positive for mannan in the less-sensitive Pastorex Candida test. The controls were negative for both beta(1-3) glucan (<20 pg/ml) and mannan (<2.5 ng/ml). IgG1 anti-CW and IgG2 anti-PPM antibodies were the most discriminatory antibodies. The ratio of IgG1 anti-CW to IgG2 anti-PPM was significantly lower in nonsurviving patients than in the other patients within the first week of candidiasis (P = 0.019). The IgG2 levels of anti-CW(IO4) and antiglucan antibodies correlated strongly (r = 0.681; P < 0.0001), and the absence of these antibodies was associated with increased levels of beta(1-3) glucan. Increased levels of IgG1 anti-CW or IgG2 anti-PPM antibodies (titer of > or = 3 logs) or of a combination of the two antibodies (log sum, > or = 5) showed 92% sensitivity, 100% specificity, and positive predictive values. In conclusion, beta(1-3) glucan and the two subclass antibodies appear to be early specific markers for the laboratory diagnosis of candidiasis. Furthermore, the kinetics of beta(1-3) glucan appearance in serum may assist in evaluating the therapeutic efficacy of antifungal treatments.

Systemic candidiasis in a dog

Candida albicans is a common cause of nosocomial infections in humans, but there are few reports of systemic candidiasis in dogs. This report describes an 11-year-old spayed female Scottish Terrier with systemic candidiasis. The diagnosis was made on the basis of results of microbiologic culture of specimens from urine and venous catheters and histologic examination of tissues obtained post mortem. Factors that predisposed the dog of this report to systemic candidiasis included diabetes mellitus, corticosteroid and broad-spectrum antimicrobial administration, venous and urinary catheterization, and administration of nutrition parenterally. The development of pyrexia and leukocytosis in dogs with risk factors that predispose to Candida spp infections warrants evaluation via microbial culture of specimens from urine and vascular catheters used in those dogs.

Candidemia: The Impact of Antifungal Prophylaxis in a Surgical Intensive Care Unit

BACKGROUND

Candidemia is fourfold more common in 1990 compared to 1980. In addition, a shift to non-albicans species has occurred in some institutions. Antifungal prophylaxis (AP) is effective in high-risk patients including critically ill surgical patients, but its use has been attributed to a resultant shift to non-albicans candida species. We hypothesized that the use of fluconazole prophylaxis would lead to a decreased incidence of candidemia but a possible increased incidence of resistant species of Candida, especially Candida glabrata (CG).

METHODS

From 1990 to 2002, all patients with candidemia (C) in the surgical intensive care unit (SICU) of a large tertiary care hospital were identified and reviewed retrospectively. Antifungal prophylaxis began in 2000 for high-risk patients. The periods were separated into PRE (1990-2000), and POST prophylaxis (2000-2002).

RESULTS

Excluding the year of the trial studying prophylaxis, (1998; five cases of C) a total of 83 patients developed candidemia: 69 PRE (83%) (1.94/1000 patient days) and 14 POST (17%) (0.76/1000 patient days) (OR 0.44; 95% CI 0.25, 0.78; p = 0.004). In the PRE period C. albicans (45%) and CG (30%) were predominant, whereas in the POST period, CG (9/14, 64%) (p = 0.05), and C. albicans (3/14, 21%) were common. Non-albicans species were 38/69 (55%) PRE and 11/14 (79%) POST, p = 0.14. Mortality in the group was 43/83 (52%) and did not differ PRE/POST or based on treatment. Predictors of SICU mortality (model r2 = 0.61) included hospital length of stay (LOS) (OR 1.14, CI 1.04, 1.25), fever (OR 51.2, CI 2.46, 1064), and broad-spectrum antibiotics (OR 69.7, CI 2.08, 2351), whereas post-transplantation status (OR 0.005, CI 0.00, 0.56), blood sugar <180 mg/dL (OR 0.03, CI 0.01, 0.81), and fungal prophylaxis (OR 0.03, CI 0.01, 0.58) were associated with a decreased risk of mortality.

CONCLUSIONS

Unfortunately, the mortality of candidemia remains high in SICU patients (52%). In the SICU, risk factors for candidemia and mortality are common. However, antifungal prophylaxis has significantly decreased the annual incidence of candidemia without a statistically significant shift to non-albicans pathogens.

Candida albicans strain carriage in patients and nursing staff of an intensive care unit: a study of morphotypes and resistotypes

Candida albicans carriage of patients and nursing staff of an intensive care unit (ICU) was studied over an 8-month period. Swabs were taken at weekly intervals from multiple sites from patients. None of the patients had clinical Candida infection at the time of the first sampling. The hands and mouth of the nursing staff were sampled at fortnightly intervals. Of the 68 patients investigated for varying periods, 37 (54%) yielded C. albicans from one or more body sites, resulting in the isolation of 269 strains. Nosocomial acquisition of C. albicans was recorded in seven (19%) patients. The frequency of C. albicans isolation increased with extended stay in ICU. Sixteen of the 180 samples taken from hands and mouth of nursing staff, yielded C. albicans, 12 of which came from the mouth. Morphotyping of 88 randomly selected strains of C. albicans originating from 31 patients yielded 34 morphotypes. There appeared to be no preference for any morphotype to colonize a particular anatomic site. Based on the susceptibility results, nine resistotypes were recognized. No correlation was apparent between any specific morphotype and resistotype patterns. The differences in morphotype and resistogram patterns of C. albicans isolates originating from same patients over a period of time suggest that some of the patients were colonized with more than one strain. Similarities in the morphotype and resistotype patterns of C. albicans strains isolated from patients and nursing staff tend to suggest possibility of exogenous acquisition.

A "clean" technique for managing bleeding duodenal ulcer with a new aortic prosthesis: endoscopic-assisted repair of bleeding duodenal ulcer

Aortic graft infection is one of the most dreaded surgical complications. In the perioperative patient with fresh aortic prosthesis, this is a particularly complex problem. Opening the bowel changes an operation to a "clean-contaminated" or "contaminated" case. This increases the risk of all infectious complications in the patient. Theoretically, our method of repair reduces the risk of infection by eliminating the duodenotomy. The direct visualization with the endoscope replaces the need to open the potentially contaminated bowel and reduces the risk of bacterial translocation and bacteremia. By not opening the bowel, this keeps the case "clean," and likely reduces the risk of contamination and subsequent infection of the prosthetic graft. As the potential morbidity of aortic graft infection is so devastating, and now that we have the available technology and operative skill, we propose our technique as a potential alternative to possibly reduce the incidence of aortic graft infection.

Epidemiologia das infecções hematogênicas por Candida spp

O gênero Candida spp é responsável por cerca de 80% das infecções fúngicas no ambiente hospitalar e constitui causa relevante de infecções de corrente sanguínea. Nos Estados Unidos da América, Candida spp é a quarta causa mais comum de infecções de corrente sanguínea, respondendo por cerca de 8% dos casos das infecções documentadas neste sítio. Espécies não-albicans respondem hoje por ao menos 50% das infecções invasivas por Candida spp, apresentando peculiaridades de história natural e sensibilidade a antifúngicos. A mortalidade geral de fungemias por Candida spp é da ordem de 40 a 60%, tornado esta complicação infecciosa um grande desafio para os clínicos que trabalham em hospitais terciários em diferentes países.

Progress in functional genomics approaches to antifungal drug target discovery

Antifungal drug discovery is starting to benefit from the enormous advances in the genomics field, which have occurred in the past decade. As traditional drug screening on existing targets is not delivering the long-awaited potent antifungals, efforts to use novel genetics and genomics-based strategies to aid in the discovery of novel drug targets are gaining increased importance. The current paradigm in antifungal drug target discovery focuses on basically two main classes of targets to evaluate: genes essential for viability and virulence or pathogenicity factors. Here we report on recent advances in genetics and genomics-based technologies that will allow us not only to identify and validate novel fungal drug targets, but hopefully in the longer run also to discover potent novel therapeutic agents. Fungal pathogens have typically presented significant obstacles when subjected to genetics, but the creativity of scientists in the anti-infectives field and the cross-talk with scientists in other areas is now yielding exciting new tools and technologies to tackle the problem of finding potent, specific and non-toxic antifungal therapeutics.

Role of antioxidant enzymatic defences against oxidative stress (H2O2) and the acquisition of oxidative tolerance inCandida albicans

In Candida albicans, trehalose plays an essential role as a protector of cell integrity against oxidative challenge. A double homozygous mutant, tps1/tps1, deficient in trehalose synthesis, displayed severe cell mortality when exposed to high H(2)O(2) concentrations, compared with its congenic parental (CAI-4) strain (Alvarez-Peral et al., 2002). We have examined the putative role of a set of well-known antioxidant enzymes as components of the defence mechanism against oxidative challenges. When exposed to mild non-lethal oxidative treatment (0.5 mM H(2)O(2)), a significant induction of catalase, glutathione reductase (GR), and Cu,Zn-superoxide dismutase (SOD) was recorded in tps1/tps1 exponential cultures. However, in CAI-4 cells, subjected to the same conditions, there was only a clear activation of catalase, Mn-SOD and Cu,Zn-SOD activities. The degree of activation was always much more pronounced in the trehalose-deficient mutant than in its wild-type counterpart, except for Mn-SOD activity. After exposure to severe oxidative stress (50 mM H(2)O(2)) only GR and catalase activities increased in tps1/tps1 cultures, whereas in CAI-4 cells GR but not catalase was induced. In both cell strains, 50 mM H(2)O(2) caused inhibition of the Mn- and Cu,Zn-SOD isozymes, this inhibition being more pronounced in tps1/tps1 cells. C. albicans is able to acquire adaptive oxidative tolerance by pretreatment with a low non-stressing concentration of H(2)O(2) before exposure to a drastic oxidative challenge. When these antioxidant activities were measured during the adaptive response, a greater degree of enzymatic antioxidant induction was consistently observed in the tps1/tps1 mutant with respect to the CAI-4 strain. Together with a higher intrinsic sensitivity of tps1/tps1 cells, we suggest that this unexpected increase might be explained in terms of a compensatory mechanism to overcome the lack of endogenous trehalose upon drastic oxidative exposure, although this induction was not sufficient to improve the percentage of cell viability.

Species distribution and antifungal susceptibility profile of Candida spp. bloodstream isolates from Latin American hospitals

From March 1999 to March 2000, we conducted a prospective multicenter study of candidemia involving five tertiary care hospitals from four countries in Latin America. Yeast isolates were identified by classical methods and the antifungal susceptibility profile was determined according to the National Committee for Clinical Laboratory Standards microbroth assay method. During a 12 month-period we were able to collect a total of 103 bloodstream isolates of Candida spp. C. albicans was the most frequently isolated species accounting for 42% of all isolates. Non-albicans Candida species strains accounted for 58% of all episodes of candidemia and were mostly represented by C. tropicalis (24.2%) and C. parapsilosis (21.3%). It is noteworthy that we were able to identify two cases of C. lusitaniae from different institutions. In our casuistic, non-albicans Candida species isolates related to candidemic episodes were susceptible to fluconazole. Continuously surveillance programs are needed in order to identify possible changes in the species distribution and antifungal susceptibility patterns of yeasts that may occurs after increasing the use of azoles in Latin American hospitals.

In vitro antimicrobial activity of olive leaves

We investigated the antimicrobial effect of olive leaves against bacteria and fungi. The microorganisms tested were inoculated in various concentrations of olive leaf water extract. Olive leaf 0.6% (w/v) water extract killed almost all bacteria tested, within 3 h. Dermatophytes were inhibited by 1.25% (w/v) plant extract following a 3-day exposure whereas Candida albicans was killed following a 24 h incubation in the presence of 15% (w/v) plant extract. Olive leaf extract fractions, obtained by dialysis, that showed antimicrobial activity consisted of particles smaller than 1000 molecular rate cutoffs. Scanning electron microscopic observations of C. albicans, exposed to 40% (w/v) olive leaf extract, showed invaginated and amorphous cells. Escherichia coli cells, subjected to a similar treatment but exposed to only 0.6% (w/v) olive leaf extract showed complete destruction. These findings suggest an antimicrobial potential for olive leaves.

Candida tropicalis fungemia in a tertiary care hospital

Candida tropicalis is a frequent cause of fungemia in hospitals in Latin America. Candida albicans (33%) was the most frequently isolated species, followed by Candida parapsilosis (27%), and Candida tropicalis (24%) in tertiary care hospital in Brazil. We identified and retrospectively reviewed 27 cases of C. tropicalis fungemia that occurred at Hospital de Clinicas de Porto Alegre from 1996 to 1999. The mean age of the patients was 32 years (range 6 months to 88 years). Eight patients (29.6%) had hematological malignancy, and four (14.8%) had solid tumors. All the patients were taking broad-spectrum antibiotics, including vancomycin for at least 7 days. Antibiotics were given through a central venous catheter for the majority of the patients (77.7%). Relevant risk factors for candidemia in our patients included neutropenia (59.2%), and use of corticosteroids (37.0%) or cytotoxic drugs (40.7%). The onset of fever was the most frequent clinical manifestation (92.5%) of fungemia. Most of the patients (81.4%) were treated with amphotericin B or fluconazole. Overall mortality was 48.1%, and 7 (53.4%) of 13 deaths occurred within 10 days of the detection of candidemia. Results of the in vitro susceptibility testing of nine isolates of C. tropicalis from seven patients did not show resistance to fluconazole and amphotericin B.C. tropicalis presents as an important cause of fungemia in oncological and nononcological patients with central venous catheters taking broad-spectrum antibiotics. Although there was no evidence of resistance of C. tropicalis to amphotericin B and fluconazole, patients treated with antifungal agents presented with a high mortality rate in the hospital setting.

Disruption of mitochondrial function in Candida albicans leads to reduced cellular ergosterol levels and elevated growth in the presence of amphotericin B

A respiratory-deficient mutant of Candida albicans MEN was generated by culturing cells in medium supplemented with ethidium bromide at 37 degrees C for 5 days. The respiratory-deficient mutant (C. albicans MMU11) was incapable of growth on glycerol, had a reduced oxygen uptake rate and demonstrated an altered mitochondrial cytochrome profile. Respiratory-competent cybrids were formed by mitochondrial transfer following fusion of protoplasts with those of C. albicans ATCC 44990. Mutant MMU11 possessed lower levels of ergosterol than the parental isolates and the cybrids, and demonstrated a small but statistically significant increase in tolerance to amphotericin B. The results demonstrated that disruption of mitochondrial function in C. albicans increases the tolerance to amphotericin B, possibly mediated by a reduction in cellular ergosterol content.

Use of Fourier-transform infrared spectroscopy for typing of Candida albicans strains isolated in intensive care units

Comparative studies of Candida albicans strains are essential for proving cross-infections in epidemiological investigations. Typing of C. albicans strains is mainly based on genotypic methods. Fourier-transform infrared (FTIR) spectroscopy is described in this study as a novel phenotypic approach to the typing of C. albicans. The first step in the approach was the standardization of sample preparation (culture conditions and sampling parameters) and acquisition and classification parameters (spectral acquisition, spectral window selection, classification algorithm, and heterogeneity threshold). The second step consisted of validating the established parameters with a set of 79 strains of C. albicans isolated over 4 months from nine patients hospitalized in two intensive care units. Strains were isolated from multiple anatomical sites with repeated sampling. FTIR spectroscopy results were compared to randomly amplified polymorphic DNA (RAPD) results; this analysis showed that the amplification patterns of strains isolated from a given patient were identical and that different patients had different profiles. FTIR spectroscopy data were analyzed by hierarchical clustering performed with the second-derivative spectra. This classification revealed nine groups, one per patient. Only one spectrum out of 79 was misclassified by the FTIR spectroscopy method. RAPD and FTIR spectroscopy results were in good agreement, showing that, when nosocomial candidiasis transmission is suspected and urgent information is needed, this technique may be useful as a quick identification tool to give solid clues before confirmation by a genotypic method.

Erythromycin, an inhibitor of mitoribosomal protein biosynthesis, alters the amphotericin B susceptibility of Candida albicans

Exposure of the yeast Candida albicans to the macrolide antibiotic erythromycin (C(37)H(67)NO(13)) results in elevated tolerance to the polyene antifungal amphotericin B. Erythromycin displays no fungistatic activity against C. albicans but inhibits the synthesis of cytochromes, particularly cytochrome aa(3). Consequently there is a reduction in aerobic respiration by up to 90% when cells are exposed to 10 mg mL(-1) erythromycin. Cellular ergosterol levels are also severely reduced. Erythromycin inhibits protein biosynthesis in ribosomes (mitoribosomes) located within the mitochondrion of the yeast cell, which results in a disruption of cytochrome biosynthesis with an adverse effect on respiration. The synthesis of ergosterol is oxygen dependent and consequently ergosterol levels are depleted in erythromycin-treated C. albicans. Ergosterol is the target for amphotericin B and since there is less of this sterol in erythromycin-treated cells, there is an increase in tolerance of the antifungal agent. Our work indicates that co-administration of erythromycin and amphotericin B to control bacterial and fungal infections, respectively, may inadvertently lead to an elevation in the tolerance of C. albicans for this antifungal agent.

Simple method for screening Candida species isolates for the presence of secreted proteinases: a tool for the prediction of successful inhibitory treatment

The yeasts of the genus Candida are opportunistic pathogens associated with the rising incidence of life-threatening infections in immunocompromised individuals. Secretion of aspartic proteinases has been determined to be one of the virulence factors of the pathogenic Candida species. To analyze the extracellular proteolytic activities of a large number of Candida clinical isolates, we developed a screening system based on a solid medium containing hemoglobin as the sole nitrogen source. The cleavage of hemoglobin by the secreted proteinases results in formation of clearance zones. The visibility of such zones was enhanced by addition of an acid-base indicator. Using this system, we assessed 245 clinical isolates of Candida from patients in the hospital of the Faculty of Medicine, Palacky University, Olomouc, Czech Republic, for the presence of secreted aspartic proteases (Saps). We also used the test plates for rapid semiquantitative testing of Sap inhibitors. Most of the pepstatin analogs affected the formation of the zones of clearance as well as the growth of Candida albicans, C. tropicalis, and C. parapsilosis colonies. By contrast, the human immunodeficiency virus proteinase inhibitors saquinavir, ritonavir, nelfinavir, and indinavir had no effect on the Candida strains tested. These results are in agreement with the inhibition constants obtained for the individual inhibitors with purified Saps. Thus, the plates containing hemoglobin proved to be an appropriate tool for the rapid and reliable assessment of Sap production and inhibition.

Evolution of drug resistance in Candida albicans

The widespread deployment of antimicrobial agents in medicine and agriculture is nearly always followed by the evolution of resistance to these agents in the pathogen. With the limited availability of antifungal drugs and the increasing incidence of opportunistic fungal infections, the emergence of drug resistance in fungal pathogens poses a serious public health concern. Antifungal drug resistance has been studied most extensively with the yeast Candida albicans owing to its importance as an opportunistic pathogen and its experimental tractability relative to other medically important fungal pathogens. The emergence of antifungal drug resistance is an evolutionary process that proceeds on temporal, spatial, and genomic scales. This process can be observed through epidemiological studies of patients and through population-genetic studies of pathogen populations. Population-genetic studies rely on sampling of the pathogen in patient populations, serial isolations of the pathogen from individual patients, or experimental evolution of the pathogen in nutrient media or in animal models. Predicting the evolution of drug resistance is fundamental to prolonging the efficacy of existing drugs and to strategically developing and deploying novel drugs.

Onychomycosis: strategies to improve efficacy and reduce recurrence

Fungal infections may be difficult to treat for several reasons. It is important to obtain the correct diagnosis, and select the appropriate antifungal agent and route. General considerations that may be associated with recurrent infections are, a genetic predisposition and suboptimal bioavailability of drug, resulting in insufficient concentration at the target site. The aetiologic organism, the severity of disease, other coexisting diseases, concomitant drug intake, and the presence of fungal infection at other sites are some factors that determine the choice of antifungal therapy and its route of administration, oral vs. topical lacquer. Local factors such as the thickness of the nail, presence of lateral onychomycosis, longitudinal spike, dermatophytoma and severe onycholysis are some factors that may determine the choice of secondary measures such as mechanical or topical treatment. Booster or supplemental therapy may be of benefit when the response to initial treatment is poorer than expected and unlikely to result in complete response. Steps should be taken to reduce the possibility of recurrence once cure has been achieved.