Emerging opportunistic yeast infections

Mannose-binding lectin levels and variation during invasive candidiasis

The high morbi-mortality associated with invasive candidiasis (IC) is a persistent problem in hospitals. Mannose-binding lectin (MBL) plays a role in innate immunity through its interaction with mannosylated molecules of Candida albicans. A correlation between MBL deficiency and vulvovaginal candidiasis or peritonitis has been reported. We investigated circulating MBL levels and their evolution during the course of IC. Sixty-eight patients with proven IC, 82 hospitalized patients (HP) without evidence of infection, and 70 healthy subjects (HS) were studied in order to examine the relationship between serum MBL and IC. Serum MBL levels were measured by enzyme-linked immunosorbent assay (ELISA). MBL levels were significantly higher in IC patients than in HP and HS (p < 0.0001, p < 0.0055, respectively). A change in MBL concentrations was observed during the course of IC, with a dramatic decrease during the 2 days before positive blood culture sampling. This decrease was concomitant with the presence of high levels of circulating mannan (Mn). Like MBL levels, anti-mannan antibodies (AMn) increased after the mannanemia/blood culture period. These findings suggest a possible role of MBL during the early stage of IC. The mechanisms that regulate these observations in terms of effect and consequences on innate and adaptive immunity and the prognosis of IC require further investigation.

Recent Taxonomic Developments with Candida and Other Opportunistic Yeasts

Increases in susceptible patient populations and advances in identification methods have resulted in the continued recognition of novel yeasts as agents of human infection. Most of these agents are members of the well-recognized genera Candida, Cryptococcus, Trichosporon, and Rhodotorula. Some of these agents are "cryptic species," members of species complexes, and may not be detectable using classical carbohydrate assimilation-based methods of yeast identification. Such species require DNA- or MALDI-based methods for correct identification, although sporadic isolates may not routinely require delineation to the individual species level. The coming end of the fungal taxonomy rules requiring separate names for sexual and asexual forms of the same fungus will hopefully allow greater clarity, as names for medically important yeast can now be based on the needs of the medical mycology community and the common goal of better communication between laboratory and clinician.

Optimization of the preanalytical steps of matrix-assisted laser desorption ionization-time of flight mass spectrometry identification provides a flexible and efficient tool for identification of clinical yeast isolates in medical laboratories

We report here that modifications of the preanalytical steps of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) identification of yeasts, with regard to the original protocol provided by the manufacturers, appear to be efficient for the reliable routine identification of clinical yeast isolates in medical laboratories. Indeed, when one colony was sampled instead of five and the protein extraction protocol was modified, the performance of MALDI-TOF MS was superior to that of the API ID 32C method (discrepancies were confirmed by using molecular identification), allowing the correct identification of 94% of the 335 clinical isolates prospectively tested. We then demonstrated that the time for which the primary cultures were preincubated on CHROMagar did not impact the identification of yeasts by MALDI-TOF MS, since 95.1 and 96.2% of the 183 clinical yeast isolates prospectively tested were correctly identified after 48 and 72 h of preincubation, respectively.

Interleukin-7 ameliorates immune dysfunction and improves survival in a 2-hit model of fungal sepsis

BACKGROUND

Secondary hospital-acquired fungal infections are common in critically-ill patients and mortality remains high despite antimicrobial therapy. Interleukin-7 (IL-7) is a potent immunotherapeutic agent that improves host immunity and has shown efficacy in bacterial and viral models of infection. This study examined the ability of IL-7, which is currently in multiple clinical trials (including hepatitis and human immunodeficiency virus), to improve survival in a clinically relevant 2-hit model of fungal sepsis.

METHODS

Mice underwent cecal ligation and puncture to induce peritonitis. Four days later, surviving mice had intravenous injection with Candida albicans. Following Candida infection, mice were treated with IL-7 or saline control. The effect of IL-7 on host immunity and survival was recorded.

RESULTS

IL-7 ameliorated the loss of immune effector cells and increased lymphocyte functions, including activation, proliferation, expression of adhesion molecules, and interferon-γ production. These beneficial effects of IL-7 were associated with an increase in global immunity as reflected by an enhanced delayed type hypersensitivity response and a 1.7-fold improvement in survival.

CONCLUSIONS

The present findings showing that IL-7 improves survival in fungal sepsis, together with its previously reported efficacy in bacterial and viral infectious models, further supports its use as a novel immunotherapeutic in sepsis.

A new bromobenzyl methyl sulphoxide from marine red alga Symphyocladia latiuscula

A new bromophenol, 2,3,6-tribromo-4,5-dihydroxybenzyl methyl sulphoxide, was isolated from the EtOH extract of the marine alga Symphyocladia latiuscula. Its structure was confirmed by spectroscopic methods (1D- and 2D-NMR, HR-ESI-MS). This new bromophenol showed moderate antifungal activity against Candida albicans with MIC value of 37.5 µg mL(-1).

Rhodotorula fungemia of an intensive care unit patient and review of published cases

Rhodotorula species are commensal yeasts that have emerged as a cause of life-threatening fungemia in severely immunocompromised patients. A case of Rhodotorula mucilaginosa fungemia in a 48-year-old woman that had undergone consecutive abdominal surgeries due to ovarian cancer and bowel necrosis while she was receiving fluconazole prophylaxis is presented. Several risk factors were identified such as presence of central venous catheters, solid organ neoplasm, abdominal surgery and administration of antibiotics. Identification was performed using commercial systems. The yeast was resistant to fluconazole, posaconazole and voriconazole and to echinocandins, whereas MIC to amphotericin B was 1.5 mg/L. Furthermore, published cases of Rhodotorula spp fungemia during the last decade are reviewed. In conclusion, Rhodotorula spp must be considered a potential pathogen in patients with immunosupression and central venous catheters. Correct identification is mandatory for appropriate management, as Rhodotorula spp are resistant to antifungal agents, such as fluconazole and echinocandins.

Assessment of the antifungal susceptibility of Malassezia pachydermatis in various media using a CLSI protocol

The microdilution antifungal method (CLSI BMD, M27-A3) was used for testing the antifungal susceptibility of Malassezia species. However, optimal broth media that allow sufficient growth of M. pachydermatitis and produce reliable and reproducible MICs using the CLSI BMD protocol are yet to be established. In this study, the susceptibility of M. pachydermatis isolates to ketoconazole (KTZ), itraconazole (ITZ) and fluconazole (FLZ) was evaluated in vitro by the CLSI BMD test using Christensen's urea broth (CUB) and mRPMI 1640 containing lipid supplementation, Sabouraud dextrose broth with 1% tween 80 (SDB), and Dixon broth (DXB). A FLZ-resistant M. pachydermatis was generated in vitro and tested under the same conditions. A good growth of M. pachydermatis incubated for 48 and 72 h, respectively, was observed in CUB, SDB and DXB and not in mRPMI 1640 (p<0.001). No statistically significant differences were detected between the MIC values registered after 48 h and 72 h incubation. ITZ displayed lower MIC values than KTZ and FLZ regardless of the media employed. A large number of FLZ-resistant Malassezia strains (86.6%) was observed using DXB. A MIC>64 mg/L was observed only when the FLZ-resistant M. pachydermatis isolate was tested in SDB. Based on the results obtained herein, culture in SDB, stock inoculum suspensions of 1-5 × 10(6)CFU/ml, and an incubation time of 48 h are proposed as optimal conditions for the evaluation of the in vitro antifungal susceptibility of M. pachydermatis using a modified CLSI BMD protocol.

The airway microbiota in cystic fibrosis: a complex fungal and bacterial community--implications for therapeutic management

Background

Given the polymicrobial nature of pulmonary infections in patients with cystic fibrosis (CF), it is essential to enhance our knowledge on the composition of the microbial community to improve patient management. In this study, we developed a pyrosequencing approach to extensively explore the diversity and dynamics of fungal and prokaryotic populations in CF lower airways.

Methodology and Principal Findings

Fungi and bacteria diversity in eight sputum samples collected from four adult CF patients was investigated using conventional microbiological culturing and high-throughput pyrosequencing approach targeting the ITS2 locus and the 16S rDNA gene. The unveiled microbial community structure was compared to the clinical profile of the CF patients. Pyrosequencing confirmed recently reported bacterial diversity and observed complex fungal communities, in which more than 60% of the species or genera were not detected by cultures. Strikingly, the diversity and species richness of fungal and bacterial communities was significantly lower in patients with decreased lung function and poor clinical status. Values of Chao1 richness estimator were statistically correlated with values of the Shwachman-Kulczycki score, body mass index, forced vital capacity, and forced expiratory volume in 1 s (p = 0.046, 0.047, 0.004, and 0.001, respectively for fungal Chao1 indices, and p = 0.010, 0.047, 0.002, and 0.0003, respectively for bacterial Chao1 values). Phylogenetic analysis showed high molecular diversities at the sub-species level for the main fungal and bacterial taxa identified in the present study. Anaerobes were isolated with Pseudomonas aeruginosa, which was more likely to be observed in association with Candida albicans than with Aspergillus fumigatus.

Conclusions

In light of the recent concept of CF lung microbiota, we viewed the microbial community as a unique pathogenic entity. We thus interpreted our results to highlight the potential interactions between microorganisms and the role of fungi in the context of improving survival in CF.

Genetic deletion of dectin-1 does not affect the course of murine experimental colitis

Background

It is believed that inflammatory bowel diseases (IBD) result from an imbalance in the intestinal immune response towards the luminal microbiome. Dectin-1 is a widely expressed pattern recognition receptor that recognizes fungi and upon recognition it mediates cytokine responses and skewing of the adaptive immune system. Hence, dectin-1 may be involved in the pathogenesis of IBD.

Methods

We assessed the responses of dectin-1 deficient macrophages to the intestinal microbiota and determined the course of acute DSS and chronic Helicobacter hepaticus induced colitis in dectin-1 deficient mice.

Results

We show that the mouse intestinal microbiota contains fungi and the cytokine responses towards this microbiota were significantly reduced in dectin-1 deficient macrophages. However, in two different colitis models no significant differences in the course of inflammation were found in dectin-1 deficient mice compared to wild type mice.

Conclusions

Together our data suggest that, although at the immune cell level there is a difference in response towards the intestinal flora in dectin-1 deficient macrophages, during intestinal inflammation this response seems to be redundant since dectin-1 deficiency in mice does not affect intestinal inflammation in experimental colitis.

Significant differences in the cell-wall mannans from three Candida glabrata strains correlate with antifungal drug sensitivity

Candida glabrata is often the second or third most common cause of candidiasis after Candida albicans. C. glabrata infections are difficult to treat, often resistant to many azole antifungal agents and are associated with a high mortality rate in compromised patients. We determined the antigenic structure of the cell-wall mannoproteins from three C. glabrata strains, NBRC 0005, NBRC 0622 and NBRC 103857. (1)H NMR and methylation analyses of the acetolysis products of these mannoproteins showed a significant difference in the amount of the β-1,2-linked mannose residue and side-chain structure. The C. glabrata NBRC 103857 strain contained up to the triose side chains and the nonreducing terminal of the triose was predominantly the β-1,2-linked mannose residue. By contrast, the mannans of the two former strains possessed up to the tetraose side chains and the amount of the β-1,2-linked mannose residue was very low. Larger oligosaccharides than tetraose in the acetolysis products of these mannans were identified as incomplete cleavage fragments by analyzing methylation, (1)H NMR spectra and the α1-2,3 mannosidase degradation reaction. Resistance to the antifungal drugs itraconazole and micafungin was significantly different in these strains. Interestingly, the NBRC 103857 strain, which involved a large amount of the β-1,2-linked mannose residues, exhibited significant sensitivity to these antifungal drugs.

Combinatorial stresses kill pathogenic Candida species

Pathogenic microbes exist in dynamic niches and have evolved robust adaptive responses to promote survival in their hosts. The major fungal pathogens of humans, Candida albicans and Candida glabrata, are exposed to a range of environmental stresses in their hosts including osmotic, oxidative and nitrosative stresses. Significant efforts have been devoted to the characterization of the adaptive responses to each of these stresses. In the wild, cells are frequently exposed simultaneously to combinations of these stresses and yet the effects of such combinatorial stresses have not been explored. We have developed a common experimental platform to facilitate the comparison of combinatorial stress responses in C. glabrata and C. albicans. This platform is based on the growth of cells in buffered rich medium at 30°C, and was used to define relatively low, medium and high doses of osmotic (NaCl), oxidative (H ₂O₂) and nitrosative stresses (e.g., dipropylenetriamine (DPTA)-NONOate). The effects of combinatorial stresses were compared with the corresponding individual stresses under these growth conditions. We show for the first time that certain combinations of combinatorial stress are especially potent in terms of their ability to kill C. albicans and C. glabrata and/or inhibit their growth. This was the case for combinations of osmotic plus oxidative stress and for oxidative plus nitrosative stress. We predict that combinatorial stresses may be highly signif cant in host defences against these pathogenic yeasts.

Infectious diseases are analogous with cancer. Hypothesis and implications

We propose to disclose first degree analogous features between cancer and infectious diseases and to find out whether these similarities are superficial and negligible, due to the use of the same bodily pathways by the two categories of disease or if they represent significantly parallel characteristics. We have found several primary analogous features, predominantly regarding pathways of spread, but to some extent also concerning the interaction with the immune system. Some of the implications to our hypothesis are probably available in the recent literature, at the experimental or clinical levels. For example endostatin, an angiogenic inhibitor has been used to prevent promotion of metastasis in cancer and to reduce granulomas formation in schistosomiasis. An ECFR antagonist employed to restrain bronchial vessels proliferation in pseudomonas infection, has also been used for the treatment of lung cancer.

Oral colonization by yeasts in HIV-positive patients in Brazil

INTRODUCTION: In HIV-infected patients, colonization of the oral cavity by potential pathogenic yeast may lead to development of systemic fungemia. We evaluated the prevalence of yeast in the oral cavity of Brazilian HIV-positive patients and verified whether or not the species characterized were enzymatically active. Furthermore, the species identified were tested for their susceptibility to antifungal treatment. METHODS: Patient saliva and oropharyngeal candidiasis samples were collected from 60 seropositive HIV patients and identified by the API20C system. Enzymatic activity was evaluated by the production of proteinase and phospholipase. Susceptibility to antifungal treatments were determined using the broth microdilution method. RESULTS: the most commonly isolated species were C. albicans (51.56%) followed by non-albicans Candida species (43.73%), Trichosporon mucoides (3.12%) and Kodamaea ohmeri (1.56%). Oral colonization by association of different species was observed in 42% of the patients. Enzymatic activity was verified in most of species isolated, except for C. glabrata, C. lusitaniae and C. guilliermondii. Resistance to Fluconazole and Amphotericin B was observed in isolates of C. albicans, C. glabrata, C. parapsilosis, C. krusei, and K. ohmeri. CONCLUSION: HIV-positive patients are orally colonized by single or multiple species of yeast that are occasionally resistant to Fluconazole or Amphotericin B.

Photodynamic inactivation of biofilms formed by Candida spp., Trichosporon mucoides, and Kodamaea ohmeri by cationic nanoemulsion of zinc 2,9,16,23-tetrakis(phenylthio)-29H, 31H-phthalocyanine (ZnPc)

The biofilms formed by opportunistic yeasts serve as a persistent reservoir of infection and impair the treatment of fungal diseases. The aim of this study was to evaluate photodynamic inactivation (PDI) of biofilms formed by Candida spp. and the emerging pathogens Trichosporon mucoides and Kodamaea ohmeri by a cationic nanoemulsion of zinc 2,9,16,23-tetrakis(phenylthio)-29H,31H-phthalocyanine (ZnPc). Biofilms formed by yeasts after 48 h in the bottom of 96-well microtiter plates were treated with the photosensitizer (ZnPc) and a GaAlAs laser (26.3 J cm(-2)). The biofilm cells were scraped off the well wall, homogenized, and seeded onto Sabouraud dextrose agar plates that were then incubated at 37°C for 48 h. Efficient PDI of biofilms was verified by counting colony-forming units (CFU/ml), and the data were submitted to analysis of variance and the Tukey test (p < 0.05). All biofilms studied were susceptible to PDI with statistically significant differences. The strains of Candida genus were more resistant to PDI than emerging pathogens T. mucoides and K. ohmeri. A mean reduction of 0.45 log was achieved for Candida spp. biofilms, and a reduction of 0.85 and 0.84, were achieved for biofilms formed by T. mucoides and K. ohmeri, respectively. Therefore, PDI by treatment with nanostructured formulations cationic zinc 2,9,16,23- tetrakis (phenylthio)- 29H, 31H- phthalocyanine (ZnPc) and a laser reduced the number of cells in the biofilms formed by strains of C. albicans and non-Candida albicans as well the emerging pathogens T. mucoides and K. ohmeri.

Evaluation of the peptide nucleic acid fluorescence in situ hybridisation technology for yeast identification directly from positive blood cultures: an Italian experience

Fungaemia is an increasing nosocomial pathology. The 'gold standard' for detection of fungaemia is blood culture, but it is time-consuming and its sensitivity for early detection is low. On the other hand, yeasts present different antifungal sensitivity patterns to be quickly detected to allow an effective treatment. The aim of this study was to evaluate the diagnostic performances of PNA-FISH to directly identify yeasts from blood cultures and to compare results with those obtained by culture. A total of 176 blood cultures positive for yeasts at direct Gram stain and 24 negative blood cultures as control collected from 15 Italian hospitals, included in a network coordinated by the Medical Mycology Committee, Italian Society of Clinical Microbiology (AMCLI), were examined both by culture and PNA-FISH technology. Sensitivity of the PNA-FISH technique evaluated for five Candida species was 99.3% and specificity, 100%. Distinguishing which yeast is implicated in fungaemia and whether the infection is caused by multiple species are important for the selection of antifungal therapy. The PNA-FISH technique is a very useful approach because the test discriminates between groups of Candida species with different susceptibility pattern, particularly against azoles and echinocandins, with only a 90-minute turn-around time after the Gram-stain reading.

Safety and efficacy of liposomal amphotericin B for the empirical therapy of invasive fungal infections in immunocompromised patients

Liposomal amphotericin B is a “true” liposomal formulation of amphotericin B with greatly reduced nephrotoxicity and minimal infusion-related toxicity. This broad spectrum polyene is well tolerated and effective against most invasive fungal infections. In view of the current limitations on diagnostic capability of invasive fungal infections, most clinicians are often compelled to use antifungal drugs in an empiric manner; liposomal amphotericin B continues to play an important role in the empiric management of invasive fungal infections, despite the recent availability of several other drugs in the azole and echinocandin classes.

Rare opportunistic (non-Candida, non-Cryptococcus) yeast bloodstream infections in patients with cancer

BACKGROUND

Rare opportunistic (non-Candida, non-Cryptococcus) yeast bloodstream infections (ROYBSIs) are rare, even in cancer patients.

METHODS

We retrospectively reviewed all episodes of ROYBSIs occurring from 1998 to 2010 in our cancer center.

RESULTS

Of 2984 blood cultures positive for Candida and non-Candida yeasts, 94 (3.1%) were positive for non-Candida yeasts, representing 41 ROYBSIs (incidence, 2.1 cases/100,000 patient-days). Catheter-associated fungemia occurred in 21 (51%) patients. Breakthrough ROYBSIs occurred in 20 (49%) patients. The yeast species distribution was Rhodotorula in 21 (51%) patients, Trichosporon in 8 (20%) patients, Saccharomyces cerevisiae in 8 (20%) patients, Geotrichum in 2 (5%) patients, Pichia anomala, and Malassezia furfur in 1 patient each. All tested Trichosporon, Geotrichum, and Pichia isolates were azole-susceptible, whereas the Rhodotorula isolates were mostly azole-resistant. We noted echinocandin nonsusceptibility (minimal inhibitory concentration ≥ 2 mg/L) in all but the S. cerevisiae isolates. Most of the isolates (28/33 [85%]) were susceptible to amphotericin B. The mortality rate in all patients at 30 days after ROYBSIs diagnosis was 34%. Multivariate survival analysis revealed increased risk of death in patients with S. cerevisiae infections (hazard ratio, 3.7), Geotrichum infections (hazard ratio, 111.3), or disseminated infections (hazard ratio, 33.4) and reduced risk in patients who had catheter removal (hazard ratio, 0.1).

CONCLUSIONS

ROYBSIs are uncommon in patients with cancer, and catheters are common sources of them. Half of the ROYBSIs occurred as breakthrough infections, and in vitro species-specific resistance to echinocandins and azoles was common. Disseminated infections resulted in the high mortality rate.

Food fermentations: microorganisms with technological beneficial use

Microbial food cultures have directly or indirectly come under various regulatory frameworks in the course of the last decades. Several of those regulatory frameworks put emphasis on "the history of use", "traditional food", or "general recognition of safety". Authoritative lists of microorganisms with a documented use in food have therefore come into high demand. One such list was published in 2002 as a result of a joint project between the International Dairy Federation (IDF) and the European Food and Feed Cultures Association (EFFCA). The "2002 IDF inventory" has become a de facto reference for food cultures in practical use. However, as the focus mainly was on commercially available dairy cultures, there was an unmet need for a list with a wider scope. We present an updated inventory of microorganisms used in food fermentations covering a wide range of food matrices (dairy, meat, fish, vegetables, legumes, cereals, beverages, and vinegar). We have also reviewed and updated the taxonomy of the microorganisms used in food fermentations in order to bring the taxonomy in agreement with the current standing in nomenclature.

The monoamine oxidase A inhibitor clorgyline is a broad-spectrum inhibitor of fungal ABC and MFS transporter efflux pump activities which reverses the azole resistance of Candida albicans and Candida glabrata clinical isolates

Resistance to the commonly used azole antifungal fluconazole (FLC) can develop due to overexpression of ATP-binding cassette (ABC) and major facilitator superfamily (MFS) plasma membrane transporters. An approach to overcoming this resistance is to identify inhibitors of these efflux pumps. We have developed a pump assay suitable for high-throughput screening (HTS) that uses recombinant Saccharomyces cerevisiae strains hyperexpressing individual transporters from the opportunistic fungal pathogen Candida albicans. The recombinant strains possess greater resistance to azoles and other pump substrates than the parental host strain. A flow cytometry-based HTS, which measured increased intracellular retention of the fluorescent pump substrate rhodamine 6G (R6G) within yeast cells, was used to screen the Prestwick Chemical Library (PCL) of 1,200 marketed drugs. Nine compounds were identified as hits, and the monoamine oxidase A inhibitor (MAOI) clorgyline was identified as an inhibitor of two C. albicans ABC efflux pumps, CaCdr1p and CaCdr2p. Secondary in vitro assays confirmed inhibition of pump-mediated efflux by clorgyline. Clorgyline also reversed the FLC resistance of S. cerevisiae strains expressing other individual fungal ABC transporters (Candida glabrata Cdr1p or Candida krusei Abc1p) or the C. albicans MFS transporter Mdr1p. Recombinant strains were also chemosensitized by clorgyline to other azoles (itraconazole and miconazole). Importantly, clorgyline showed synergy with FLC against FLC-resistant C. albicans clinical isolates and a C. glabrata strain and inhibited R6G efflux from a FLC-resistant C. albicans clinical isolate. Clorgyline is a novel broad-spectrum inhibitor of two classes of fungal efflux pumps that acts synergistically with azoles against azole-resistant C. albicans and C. glabrata strains.

[Invasive fungal disease: conventional or molecular mycological diagnosis?]

Diagnosis of invasive mycoses is a difficult challenge due to the limitations and low sensitivity of traditional microbiology methods which lead to diagnostic and therapeutic delays. The aim of this review is to summarise the state of the art of the molecular diagnosis of invasive fungal disease and to clarify its current role in the clinical practice. Conventional microbiological methods could be complemented with molecular methods in the rapid and definitive identification of fungal isolates. Biomarkers (β-glucan, galactomannan) are very useful in immunocompromised patients and have been included as probable invasive mycoses by the EORTC/MSG. Nucleic acid detection is currently used as a complementary tool for diagnosis. However, PCR can be very useful in mould invasive mycoses. Finally, the combined detection using biomarkers can improve the diagnosis. However, their applicability in the microbiology laboratory is not so easy and further studies are required for the appropriate evaluation of its clinical usefulness.

The Effect of the acetone extract of Arctotis arctotoides (Asteraceae) on the growth and ultrastructure of some opportunistic fungi associated with HIV/AIDS

In this study, the effect of the acetone extract of Arctotis arctotoides (L.f.) O. Hoffm. (Asteraceae) on the growth and ultrastructure of some opportunistic fungi associated with HIV/AIDS was analyzed by means of scanning electron microscope (SEM). Remarkable morphological alterations in the fungal mycelia which were attributed to the loss of cell wall strength ranged from loss of turgidity and uniformity, collapse of entire hyphae to evident destruction of the hyphae. The elements responsible for giving the fungi their characteristic virulence were detected and quantified by energy dispersive X-ray microanalysis techniques. X-ray microanalysis showed the specific spectra of sodium, potassium and sulfur as the principal intersection of the four pathogenic fungi studied. Since these ions have the potential of fostering fungal invasion by altering the permeability of hosts' membranes, their presence was considered inherent to the pathogenicity of the opportunistic fungi. Hence, these findings indicate the potential of the crude extract of A. arctotoides in preventing fungal invasion and subsequent infection of host's membranes.

Fungicidal activity of the human peptide hepcidin 20 alone or in combination with other antifungals against Candida glabrata isolates

Candida glabrata infections are often difficult to eradicate due to the intrinsically low susceptibility to azoles of this species. In addition, C. glabrata has also been shown to be insensitive to several cationic peptides, which have been shown to be promising novel therapeutic candidates for the treatment of fungal infection. In this study, the in vitro fungicidal activity of the human cationic peptide hepcidin 20 (Hep-20) was evaluated against clinical isolates of C. glabrata with different levels of fluconazole susceptibility. Interestingly, all isolates were susceptible to Hep-20 (100-200 μg/ml) at pH 7.4, whereas the fungicidal effect of the peptide was higher (50 μg/ml) at acidic pH values. In addition, an increased antifungal activity was observed for Hep-20 with amphotericin B and a synergistic effect was demonstrated for the Hep-20/fluconazole and Hep-20/caspofungin combinations.

Are subinhibitory concentrations of antibiotics the only culprit of antibiotic resistance?

Evaluation of: Gullberg E, Cao S, Berg OG et al. Selection of resistant bacteria at very low antibiotic concentrations. PLoS Pathog. 7(7), e1002158 (2011). Subinhibitory concentrations of antibiotics and antifungals promote resistance. Antibiotic consumption including hospital use, and country use, including patients self-medications is one of the major drivers of antibiotic or antifungal resistance. However, consumption of antibiotics should be distinguished between the hospital and community. Hospital consumption, poor hospital hygiene and intrahospital transfer have been determined as major risk factors for development of resistance. The correlation between resistance and consumption in the community is not so clear. Therefore consumption of antibiotics and antifungals alone cannot explain the selection of resistant bacterial and fungal mutants and other factors have to be investigated.

The rising problem of antimicrobial resistance in the intensive care unit

Mainly due to its extremely vulnerable population of critically ill patients, and the high use of (invasive) procedures, the intensive care unit (ICU) is the epicenter of infections. These infections are associated with an important rise in morbidity, mortality, and healthcare costs. The additional problem of multidrug-resistant pathogens boosts the adverse impact of infections in ICUs. Several factors influence the rapid spread of multidrug-resistant pathogens in the ICU, e.g., new mutations, selection of resistant strains, and suboptimal infection control. Among gram-positive organisms, the most important resistant microorganisms in the ICU are currently methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. In gram-negative bacteria, the resistance is mainly due to the rapid increase of extended-spectrum Beta-lactamases (ESBLs) in Klebsiella pneumonia, Escherichia coli, and Proteus species and high level third-generation cephalosporin Beta-lactamase resistance among Enterobacter spp. and Citrobacter spp., and multidrug resistance in Pseudomonas aeruginosa and Acinetobacter species. To conclude, additional efforts are needed in the future to slow down the emergence of antimicrobial resistance. Constant evaluation of current practice on basis of trends in MDR and antibiotic consumption patterns is essential to make progress in this problematic matter.

Fatal septic shock due to a disseminated chronic form of paracoccidioidomycosis in an aged woman

Once rare, septic shock (SS) due to disseminated fungal infections has been increasingly reported due to a growing number of immunocompromised patients, but remains rare in non-immune-compromised individuals. In paracoccidioidomycosis, it has been described in only three patients with the severe, acute form of the disease. We describe the development of a refractory, fatal septic shock due to a severe disseminated chronic form of paracoccidioidomycosis in an older woman without any other microbial insults. A striking event in the evolution of her case was the severe depletion of lymphocytes from the peripheral blood and lymphoid organs. Lymphocyte depletion due to apoptosis is described in the late phase of sepsis and can contribute both to immunosuppression and the progression of SS. The possible mechanisms involved in the induction of SS in the chronic form of paracoccidioidomycosis are discussed.

Wild-type Drosophila melanogaster as a model host to analyze nitrogen source dependent virulence of Candida albicans

The fungal pathogen Candida albicans is a common cause of opportunistic infections in humans. We report that wild-type Drosophila melanogaster (OrR) flies are susceptible to virulent C. albicans infections and have established experimental conditions that enable OrR flies to serve as model hosts for studying C. albicans virulence. After injection into the thorax, wild-type C. albicans cells disseminate and invade tissues throughout the fly, leading to lethality. Similar to results obtained monitoring systemic infections in mice, well-characterized cph1Δ efg1Δ and csh3Δ fungal mutants exhibit attenuated virulence in flies. Using the OrR fly host model, we assessed the virulence of C. albicans strains individually lacking functional components of the SPS sensing pathway. In response to extracellular amino acids, the plasma membrane localized SPS-sensor (Ssy1, Ptr3, and Ssy5) activates two transcription factors (Stp1 and Stp2) to differentially control two distinct modes of nitrogen acquisition (host protein catabolism and amino acid uptake, respectively). Our results indicate that a functional SPS-sensor and Stp1 controlled genes required for host protein catabolism and utilization, including the major secreted aspartyl protease SAP2, are required to establish virulent infections. By contrast, Stp2, which activates genes required for amino acid uptake, is dispensable for virulence. These results indicate that nutrient availability within infected hosts directly influences C. albicans virulence.

The Candida genome database incorporates multiple Candida species: multispecies search and analysis tools with curated gene and protein information for Candida albicans and Candida glabrata

The Candida Genome Database (CGD, http://www.candidagenome.org/) is an internet-based resource that provides centralized access to genomic sequence data and manually curated functional information about genes and proteins of the fungal pathogen Candida albicans and other Candida species. As the scope of Candida research, and the number of sequenced strains and related species, has grown in recent years, the need for expanded genomic resources has also grown. To answer this need, CGD has expanded beyond storing data solely for C. albicans, now integrating data from multiple species. Herein we describe the incorporation of this multispecies information, which includes curated gene information and the reference sequence for C. glabrata, as well as orthology relationships that interconnect Locus Summary pages, allowing easy navigation between genes of C. albicans and C. glabrata. These orthology relationships are also used to predict GO annotations of their products. We have also added protein information pages that display domains, structural information and physicochemical properties; bibliographic pages highlighting important topic areas in Candida biology; and a laboratory strain lineage page that describes the lineage of commonly used laboratory strains. All of these data are freely available at http://www.candidagenome.org/. We welcome feedback from the research community at candida-curator@lists.stanford.edu.

Oral Candida albicans isolates from HIV-positive individuals have similar in vitro biofilm-forming ability and pathogenicity as invasive Candida isolates

Background

Candida can cause mucocutaneous and/or systemic infections in hospitalized and immunosuppressed patients. Most individuals are colonized by Candida spp. as part of the oral flora and the intestinal tract. We compared oral and systemic isolates for the capacity to form biofilm in an in vitro biofilm model and pathogenicity in the Galleria mellonella infection model. The oral Candida strains were isolated from the HIV patients and included species of C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, C. krusei, C. norvegensis, and C. dubliniensis. The systemic strains were isolated from patients with invasive candidiasis and included species of C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, C. lusitaniae, and C. kefyr. For each of the acquired strains, biofilm formation was evaluated on standardized samples of silicone pads and acrylic resin. We assessed the pathogenicity of the strains by infecting G. mellonella animals with Candida strains and observing survival.

Results

The biofilm formation and pathogenicity in Galleria was similar between oral and systemic isolates. The quantity of biofilm formed and the virulence in G. mellonella were different for each of the species studied. On silicone pads, C. albicans and C. dubliniensis produced more biofilm (1.12 to 6.61 mg) than the other species (0.25 to 3.66 mg). However, all Candida species produced a similar biofilm on acrylic resin, material used in dental prostheses. C. albicans, C. dubliniensis, C. tropicalis, and C. parapsilosis were the most virulent species in G. mellonella with 100% of mortality, followed by C. lusitaniae (87%), C. novergensis (37%), C. krusei (25%), C. glabrata (20%), and C. kefyr (12%).

Conclusions

We found that on silicone pads as well as in the Galleria model, biofilm formation and virulence depends on the Candida species. Importantly, for C. albicans the pathogenicity of oral Candida isolates was similar to systemic Candida isolates, suggesting that Candida isolates have similar biofilm-forming ability and virulence regardless of the infection site from which it was isolated.

Selection of orlistat as a potential inhibitor for lipase from Candida species

Infections caused by Candida species manifest in a number of diseases, including candidemia, vulvovaginal candidiasis, endocarditis, and peritonitis. Candida species have been reported to possess lipolytic activity due to the secretion of lipolytic enzymes such as esterases, lipases and phospholipases. Extra-cellular hydrolytic enzymes seem to play an important role in Candida overgrowth. Candidiasis is commonly treated with antimycotics such as clotrimazole and nystatin. The antimycotics bind to a major component of the fungal cell membrane (ergosterol), forming pores that lead to death of the fungus. However, the secondary effects caused during such treatment have aroused a need to develop a treatment based on lipase inhibition. Nonetheless, no such lipase inhibitors for candidiasis treatment are currently available. Thus, we have performed a docking study with the natural inhibitor, orlistat or tetrahydrolipstatin. Our results have shown ten possible binding inhibitors to Candida rugosa lipase (CRL), out of which one possibility was selected, based on the weakest interatomic distance of 2.7 Å. Therefore, we propose the selection and design of a potential inhibitor candidate, orlistat for the treatment of candidiasis infections. However, this study has to be supported with in vitro and in vivo experiments to demonstrate the effectiveness of orlistat in lipase inhibition.

Toll-like receptor 9 modulates macrophage antifungal effector function during innate recognition of Candida albicans and Saccharomyces cerevisiae

Phagocytic responses are critical for effective host defense against opportunistic fungal pathogens. Macrophages sample the phagosomal content and orchestrate the innate immune response. Toll-like receptor 9 (TLR9) recognizes unmethylated CpG DNA and is activated by fungal DNA. Here we demonstrate that specific triggering of TLR9 recruitment to the macrophage phagosomal membrane is a conserved feature of fungi of distinct phylogenetic origins, including Candida albicans, Saccharomyces cerevisiae, Malassezia furfur, and Cryptococcus neoformans. The capacity to trigger phagosomal TLR9 recruitment was not affected by a loss of fungal viability or cell wall integrity. TLR9 deficiency has been linked to increased resistance to murine candidiasis and to restriction of fungal growth in vivo. Macrophages lacking TLR9 demonstrate a comparable capacity for phagocytosis and normal phagosomal maturation compared to wild-type macrophages. We now show that TLR9 deficiency increases macrophage tumor necrosis factor alpha (TNF-α) production in response to C. albicans and S. cerevisiae, independent of yeast viability. The increase in TNF-α production was reversible by functional complementation of the TLR9 gene, confirming that TLR9 was responsible for negative modulation of the cytokine response. Consistently, TLR9 deficiency enhanced the macrophage effector response by increasing macrophage nitric oxide production. Moreover, microbicidal activity against C. albicans and S. cerevisiae was more efficient in TLR9 knockout (TLR9KO) macrophages than in wild-type macrophages. In conclusion, our data demonstrate that TLR9 is compartmentalized selectively to fungal phagosomes and negatively modulates macrophage antifungal effector functions. Our data support a model in which orchestration of antifungal innate immunity involves a complex interplay of fungal ligand combinations, host cell machinery rearrangements, and TLR cooperation and antagonism.

Evaluation of repetitive sequence PCR and PCR-mass spectrometry for the identification of clinically relevant Candida species

The application of molecular diagnostic methods may improve the timeliness and accuracy with which fungi are identified. A total of 76 well-characterized reference strains of clinically relevant Candida species and 61 clinical Candida isolates were tested by repetitive sequence PCR (rep-PCR) and PCR followed by electrospray ionization mass spectrometry (PCR/ESI-MS) and results compared against internal transcribed spacer (ITS) ribosomal RNA gene sequencing as a reference standard. Both rep-PCR and PCR/ESI-MS correctly identified 51 isolates to the species level. When method performance was evaluated based only on genospecies included in the reference libraries, both methods yielded an accuracy of 98.1%. It may be concluded that rep-PCR and PCR/ESI-MS are highly effective at identifying clinical isolates of Candida to the species level. These methods hold promise for improving the speed and accuracy of identification of Candida spp. in clinical mycology laboratories.

Lindnera (Pichia) fabianii blood infection after mesenteric ischemia

Lindnera (Pichia) fabianii (teleomorph of Candida fabianii) is a yeast species rarely involved in human infections. This report describes the first known human case of a Lindnera fabianii blood infection after mesenteric ischemia. The 53-year-old patient was hospitalized in the intensive care unit after a suicide attempt and was suffering from a mesenteric ischemia and acute renal failure. Lindnera fabianii was recovered from an oropharyngeal swab, then isolated from stool and urine samples before the diagnosis of the blood infection. Caspofungin intravenous treatment was associated with a successful outcome. Final unequivocal identification of the strain was done by sequencing the internal transcribed spacer (ITS) region, and regions of 18S rDNA gene and of the translation elongation factor-1α gene. Until our work, the genomic databases did not contain the complete ITS region of L. fabianii as a single nucleotide sequence (encompassing ITS1, the 5.8S rDNA and ITS2), and misidentification with other yeast species, e.g., Lindnera (Pichia) mississippiensis, could have occurred. Our work demonstrates that the usual DNA barcoding method based on sequencing of the ITS region may fail to provide the correct identification of some taxa, and that partial sequencing of the EF1α gene may be much more effective for the accurate delineation and molecular identification of new emerging opportunistic yeast pathogens.

Modulation of morphogenesis in Candida albicans by various small molecules

The pathogenic yeast Candida albicans, a member of the mucosal microbiota, is responsible for a large spectrum of infections, ranging from benign thrush and vulvovaginitis in both healthy and immunocompromised individuals to severe, life-threatening infections in immunocompromised patients. A striking feature of C. albicans is its ability to grow as budding yeast and as filamentous forms, including hyphae and pseudohyphae. The yeast-to-hypha transition contributes to the overall virulence of C. albicans and may even constitute a target for the development of antifungal drugs. Indeed, impairing morphogenesis in C. albicans has been shown to be a means to treat candidiasis. Additionally, a large number of small molecules such as farnesol, fatty acids, rapamycin, geldanamycin, histone deacetylase inhibitors, and cell cycle inhibitors have been reported to modulate the yeast-to-hypha transition in C. albicans. In this minireview, we take a look at molecules that modulate morphogenesis in this pathogenic yeast. When possible, we address experimental findings regarding their mechanisms of action and their therapeutic potential. We discuss whether or not modulating morphogenesis constitutes a strategy to treat Candida infections.

Milestones in Candida albicans gene manipulation

In the United States, candidemia is one of the most common hospital-acquired infections and is estimated to cause 10,000 deaths per year. The species Candida albicans is responsible for the majority of these cases. As C. albicans is capable of developing resistance against the currently available drugs, understanding the molecular basis of drug resistance, finding new cellular targets, and further understanding the overall mechanism of C. albicans pathogenesis are important goals. To study this pathogen it is advantageous to manipulate its genome. Numerous strategies of C. albicans gene manipulation have been introduced. This review evaluates a majority of these strategies and should be a helpful guide for researchers to identify gene targeting strategies to suit their requirements.