Epidemiology of invasive candidiasis

Clinical comparison of the Bactec Mycosis IC/F, BacT/Alert FA, and BacT/Alert FN blood culture vials for the detection of candidemia

The present study analyzed the performance of Bactec Mycosis IC/F, BacT/Alert FA, and BacT/Alert FN vials in detection and time to detection (TTD) of Candida spp. in 179 simultaneous blood cultures. The Mycosis IC/F, BacT/Alert FA, and BacT/Alert FN vials could detect Candida spp. in 144 (80.45%) of 179, 149 (83.24%) of 179, and 8 (4.47%) of 179 samples, respectively. With the presence of antifungal therapy, the numbers of positive vials were higher in BacT/Alert FA compared to Mycosis IC/F, 87/99 versus 73/99, respectively (P < 0.05). TTD (SD) for C. albicans was shorter in Mycosis IC/F than in BacT/Alert FA vials without antifungal therapy, 20.89 (9.33) versus 28.26 (9.77), respectively (P < 0.01). The detection of Candida spp., with concomitant bacteremia, was higher in Mycosis IC/F than in BacT/Alert FA vials, 28/30 and 19/30, respectively (P = 0.01). The present data show that the use of Bactec Mycosis IC/F together with BacT/Alert FA vials might improve the detection of Candida spp.

Differential in vivo activities of anidulafungin, caspofungin, and micafungin against Candida glabrata isolates with and without FKS resistance mutations

We recently observed that the micafungin MICs for some Candida glabrata fks hot spot mutant isolates are less elevated than those for the other echinocandins, suggesting that the efficacy of micafungin may be differentially dependent on such mutations. Three clinical C. glabrata isolates with or without (S3) fks hot spot mutations R83 (Fks2p-S663F) and RR24 (Fks1p-S629P) and low, medium, and high echinocandin MICs, respectively, were evaluated to assess the in vivo efficacy in an immunocompetent mouse model using three doses of each echinocandin. Drug concentrations were determined in plasma and kidneys by high-performance liquid chromatography (HPLC). A pharmacokinetic-pharmacodynamic mathematical model was used to define the area under the concentration-time curve (AUC) that produced half- and near-maximal activity. Micafungin was equally efficacious against the S3 and R83 isolates. The estimates for the AUCs of each echinocandin that induced half-maximal effect (E(50)s) were 194.2 and 53.99 mg · h/liter, respectively. In contrast, the maximum effect (E(max)) for caspofungin was higher against S3 than R83, but the estimates for E(50) were similar (187.1 and 203.5 mg · h/liter, respectively). Anidulafungin failed to induce a ≥1-log reduction for any of the isolates (AUC range, 139 to 557 mg · h/liter). None of the echinocandins were efficacious in mice challenged with the RR24 isolate despite lower virulence (reduced maximal growth, prolonged lag phase, and lower kidney burden). The AUC associated with half-maximal effect was higher than the average human exposure for all drug-dose-bug combinations except micafungin and the R83 isolate. In conclusion, differences in micafungin MICs are associated with differential antifungal activities in the animal model. This study may have implications for clinical practice and echinocandin breakpoint determination, and further studies are warranted.

Synthesis and antifungal activity of a new series of 2-(1H-imidazol-1-yl)-1-phenylethanol derivatives

A new series of aromatic ester and carbamate derivatives of 2-(1H-imidazol-1-yl)-1-phenylethanol were synthesized and evaluated for their antifungal activity towards Candida albicans and non-albicans Candida species strains. The aromatic biphenyl ester derivatives 6a-c were more active than the reference compound fluconazole. 6c possesses a MIC mean values of 1.7 ± 1.4 μg mL(-1)vs C. albicans and 1.9 ± 2.0 μg mL(-1)vs non-albicans Candida species strains. The racemic mixtures of 6a, b were purified to afford the pure enantiomers. The (-) isomers were up to 500 times more active than (+) isomers. (-)-6a and (-)-6b were thirty and ninety times more active than fluconazole towards C. krusei strain respectively. The racemates of 6a-c showed low cytotoxicity against human monocytic cell line (U937) with 6a demonstrating a CC(50) greater than 128 μg mL(-1).

European expert opinion on the management of invasive candidiasis in adults

This report discusses the present status of antifungal therapy and treatment options for candidaemia, considered by experts in the field in Europe. A conference of 26 experts from 13 European countries was held to discuss strategies for the treatment and prevention of invasive candidiasis, with the aim of providing a review on optimal management strategies. Published and unpublished comparative trials on antifungal therapy were analysed and discussed. Commonly asked questions about the management of candidaemia were selected, and possible responses to these questions were discussed. Panellists were then asked to respond to each question by using a touchpad answering system. After the initial conference, the viewpoint document has been reviewed and edited to include new insights and developments since the initial meeting. For many situations, consensus on treatment could not be reached, and the responses indicate that treatment is likely to be modified on a patient-to-patient basis, depending on factors such as degree of illness, prior exposure to azole antifungals, and the presence of potentially antifungal drug-resistant Candida species.

Use of fungal derived polysaccharide-conjugated particles to probe Dectin-1 responses in innate immunity

The number of life-threatening fungal infections has risen in immunocompromised patients, and identification of the rules that govern an appropriate immune response is essential to develop better diagnostics and targeted therapeutics. The outer cell wall component on pathogenic fungi consists of β-1,3-glucan, and Dectin-1, a pattern recognition receptor present on the cell surface of innate immune cells, binds specifically to this carbohydrate. A barrier in understanding the exact immunological response to pathogen-derived carbohydrate epitopes is the presence of multiple types of carbohydrate moieties on fungal cell walls. To dissect the immunological mechanisms used to recognize pathogens, a system of "fungal like particles" was developed that consisted of polystyrene beads, which mimicked the three dimensional shape of the fungus, coated covalently with purified β-1,3-glucan derived from Saccharomyces cerevisiae. The morphology of the β-1,3-glucan layer was examined by immunofluorescence, flow cytometery, and immuno-transmission electron microscopy. The covalent linkages of the β-1,3-glucan to the polystyrene surface were stable after subjecting the beads to detergents. By pre-treating β-1,3-glucan beads with laminarinase, a specific β-1,3-gluconase, the reactivity of the anti-β-1,3-glucan antibody was abrogated in comparison to treatment with proteinase K indicating that the coating of these beads was predominantly β-1,3-glucan. TNF-α was also measured by stimulating bone-marrow derived macrophages with the β-1,3-glucan beads, and showed a dose dependent response compared to soluble β-glucan, insoluble β-1,3-glucan, uncoated beads, and soluble β-1,3-glucan mixed with uncoated beads. Finally, β-1,3-glucan beads were incubated with GFP-Dectin-1 expressing macrophages and imaged using confocal microscopy. β-1,3-beads were taken up within minutes and retained Dectin-1 recruitment to the phagosome as compared to uncoated beads. These data describe a unique fungal-like particle system that will permit immunologists to probe the critical steps in early recognition of pathogen-derived fungal carbohydrate antigens by innate immune cells.

Antifungal resistance and new strategies to control fungal infections

Despite improvement of antifungal therapies over the last 30 years, the phenomenon of antifungal resistance is still of major concern in clinical practice. In the last 10 years the molecular mechanisms underlying this phenomenon were extensively unraveled. In this paper, after a brief overview of currently available antifungals, molecular mechanisms of antifungal resistance will be detailed. It appears that major mechanisms of resistance are essential due to the deregulation of antifungal resistance effector genes. This deregulation is a consequence of point mutations occurring in transcriptional regulators of these effector genes. Resistance can also follow the emergence of point mutations directly in the genes coding antifungal targets. In addition we further describe new strategies currently undertaken to discover alternative therapy targets and antifungals. Identification of new antifungals is essentially achieved by the screening of natural or synthetic chemical compound collections. Discovery of new putative antifungal targets is performed through genome-wide approaches for a better understanding of the human pathogenic fungi biology.

Interactions of Bacteria and Fungi at the Surface

The increased life span of humans and the dynamic development of Biomaterials' industry have led to widespread use of implants in modern medicine. Microorganisms, mostly opportunistic flora,are able to adapt perfectly to the changing environment of their host. Bacteria, once regarded as non-pathogenic, successfully bind to artificial surfaces resulting in diseases that are difficult to treat. The Chapter discusses the process of microbial adhesion to the surfaces. It provides the brief description of the most important infections of humans, which result from the microbial colonization of implanted biomaterials. This adhesion is characterized in the context of physicochemical and biological interactions between microorganism and the surface. We describe the effects of environmental factors and the contribution of bacterial/fungal cell structures on microbial adhesion. Finally, the Chapter presents the most important aspects of interactions between bacteria and charged surfaces.

Early diagnosis of candidemia in intensive care unit patients with sepsis: a prospective comparison of (1→3)-β-D-glucan assay, Candida score, and colonization index

Introduction

The culture-independent serum (1→3)-β-D-glucan (BG) detection test may allow early diagnosis of invasive fungal disease, but its clinical usefulness needs to be firmly established. A prospective single-center observational study was conducted to compare the diagnostic value of BG assay, Candida score (CS), and colonization index in intensive care unit (ICU) patients at risk for Candida sepsis.

Methods

Of 377 patients, consecutively admitted to ICU for sepsis, 95 patients having an ICU stay of more than five days were studied. Blood specimens for fungal culture and BG measurement were obtained at the onset of clinical sepsis. For CS and colonization index calculations, surveillance cultures for Candida growth, and/or clinical data were recorded.

Results

Sixteen (16.8%) patients were diagnosed with proven invasive fungal infection, 14 with candidiasis (13 candidemia and 1 mediastinitis) and 2 with pulmonary aspergillosis or fusariosis. Of 14 invasive Candida-infection patients, 13 had a serum sample positive for BG, 10 had a CS value ≥3, and 7 a colonization index ≥0.5. In the 12 candidemic patients, a positive BG result was obtained 24 to 72 hrs before a culture-documented diagnosis of invasive candidiasis. The positive and negative predictive values for the BG assay were higher than those of CS and colonization index (72.2% versus 57.1% and 27.3%; and 98.7% versus 97.2% and 91.7%, respectively).

Conclusions

A single-point BG assay based on a blood sample drawn at the sepsis onset, alone or in combination withCS, may guide the decision to start antifungal therapy early in patients at risk for Candida infection.

Discovery of a novel class of orally active antifungal beta-1,3-D-glucan synthase inhibitors

The echinocandins are a class of semisynthetic natural products that target β-1,3-glucan synthase (GS). Their proven clinical efficacy combined with minimal safety issues has made the echinocandins an important asset in the management of fungal infection in a variety of patient populations. However, the echinocandins are delivered only parenterally. A screen for antifungal bioactivities combined with mechanism-of-action studies identified a class of piperazinyl-pyridazinones that target GS. The compounds exhibited in vitro activity comparable, and in some cases superior, to that of the echinocandins. The compounds inhibit GS in vitro, and there was a strong correlation between enzyme inhibition and in vitro antifungal activity. In addition, like the echinocandins, the compounds caused a leakage of cytoplasmic contents from yeast and produced a morphological response in molds characteristic of GS inhibitors. Spontaneous mutants of Saccharomyces cerevisiae with reduced susceptibility to the piperazinyl-pyridazinones had substitutions in FKS1. The sites of these substitutions were distinct from those conferring resistance to echinocandins; likewise, echinocandin-resistant isolates remained susceptible to the test compounds. Finally, we present efficacy and pharmacokinetic data on an example of the piperazinyl-pyridazinone compounds that demonstrated efficacy in a murine model of Candida glabrata infection.

Diagnostic issues, clinical characteristics, and outcomes for patients with fungemia

This study investigated microbiological, clinical, and management issues and outcomes for Danish fungemia patients. Isolates and clinical information were collected at six centers. A total of 334 isolates, 316 episodes, and 305 patients were included, corresponding to 2/3 of the national episodes. Blood culture positivity varied by system, species, and procedure. Thus, cases with concomitant bacteremia were reported less commonly by BacT/Alert than by the Bactec system (9% [11/124 cases] versus 28% [53/192 cases]; P < 0.0001), and cultures with Candida glabrata or those drawn via arterial lines needed longer incubation. Species distribution varied by age, prior antifungal treatment (57% occurrence of C. glabrata, Saccharomyces cerevisiae, or C. krusei in patients with prior antifungal treatment versus 28% occurrence in those without it; P = 0.007), and clinical specialty (61% occurrence of C. glabrata or C. krusei in hematology wards versus 27% occurrence in other wards; P = 0.002). Colonization samples were not predictive for the invasive species in 11/100 cases. Fifty-six percent of the patients had undergone surgery, 51% were intensive care unit (ICU) patients, and 33% had malignant disease. Mortality increased by age (P = 0.009) and varied by species (36% for C. krusei, 25% for C. parapsilosis, and 14% for other Candida species), severity of underlying disease (47% for ICU patients versus 24% for others; P = 0.0001), and choice but not timing of initial therapy (12% versus 48% for patients with C. glabrata infection receiving caspofungin versus fluconazole; P = 0.023). The initial antifungal agent was deemed suboptimal upon species identification in 15% of the cases, which would have been 6.5% if current guidelines had been followed. A large proportion of Danish fungemia patients were severely ill and received suboptimal initial antifungal treatment. Optimization of diagnosis and therapy is possible.

Epidemiology and treatment approaches in management of invasive fungal infections

Over the past 20 years, the number of invasive fungal infections has continued to persist, due primarily to the increased numbers of patients subjected to severe immunosuppression. Despite the development of more active, less toxic antifungal agents and the standard use of antifungal prophylaxis, invasive fungal infections (especially invasive mold infections) continue to be a significant factor in hematopoietic cell and solid organ transplantation outcomes, resulting in high mortality rates. Since the use of fluconazole as standard prophylaxis in the hematopoietic cell transplantation setting, invasive candidiasis has come under control, but no mold-active antifungal agent (except for posaconazole in the setting of acute myelogenous leukemia and myelodysplastic syndrome) has been shown to improve the survival rate over fluconazole. With the advent of new azole and echinocandin agents, we have seen the emergence of more azole-resistant and echinocandin-resistant fungi. The recent increase in zygomycosis seen in the hematopoietic cell transplantation setting may be due to the increased use of voriconazole. This has implications for the empiric approach to pulmonary invasive mold infections when zygomycosis cannot be ruled out. It is imperative that an amphotericin B product, an antifungal that has never developed resistance in over 50 years, be initiated. The clinical presentations of invasive mold infections and invasive candidiasis can be nonspecific and the diagnostic tests insensitive, so a high index of suspicion and immediate initiation of empiric therapy is required. Unfortunately, our currently available serologic tests do not predict infection ahead of disease, and, therefore cannot be used to initiate “preemptive” therapy. Also, the Aspergillus galactomannan test gives a false negative result in patients receiving antimold prophylaxis, ie, virtually all of our patients with hematologic malignancy and hematopoietic cell transplant recipients. We may eventually be able to select patients at highest risk for invasive fungal infections for prophylaxis by genetic testing. However, with our current armamentarium of antifungal agents and widespread use of prophylaxis in high-risk groups (hematologic malignancy, hematopoietic cell transplantation), we continue to see high incidence and mortality rates, and our future hope lies in reversing the immunosuppression or augmenting the immune system of these severely immunocompromised hosts by developing and utilizing immunotherapy, immunoprophylaxis, and vaccines.

National surveillance of fungemia in Denmark (2004 to 2009)

A 6-year nationwide study of fungemia in Denmark was performed using data from an active fungemia surveillance program and from laboratory information systems in nonparticipating regions. A total of 2,820 episodes of fungemia were recorded. The incidence increased from 2004 to 2007 (7.7 to 9.6/100,000) and decreased slightly from 2008 to 2009 (8.7 to 8.6/100,000). The highest incidences were seen at the extremes of age (i.e., 11.3 and 37.1/100,000 for those <1 and 70 to 79 years old, respectively). The rate was higher for males than for females (10.1 versus 7.6/100,000, P = 0.003), with the largest difference observed for patients >50 years of age. The species distribution varied significantly by both age and gender. Candida species accounted for 98% of the pathogens, and C. albicans was predominant, although the proportion decreased (64.4% to 53.2%, P < 0.0001). C. glabrata ranked second, and the proportion increased (16.5% to 25.9%, P = 0.003). C. glabrata was more common in adults and females than in children and males, whereas C. tropicalis was more common in males (P = 0.020). C. krusei was a rare isolate (4.1%) except at one university hospital. Acquired resistance to amphotericin and echinocandins was rare. However, resistance to fluconazole (MIC of >4 μg/ml) occurred in C. albicans (7/1,183 [0.6%]), C. dubliniensis (2/65 [3.1%]), C. parapsilosis (5/83 [6.0%]), and C. tropicalis (7/104 [6.7%]). Overall, 70.8% of fungemia isolates were fully fluconazole susceptible, but the proportion decreased (79.7% to 68.9%, P = 0.02). The study confirmed an incidence rate of fungemia in Denmark three times higher than those in other Nordic countries and identified marked differences related to age and gender. Decreased susceptibility to fluconazole was frequent and increasing.