Invasive candidiasis: update on current pharmacotherapy options and future perspectives

Ssa1-targeted antibody prevents host invasion by Candida albicans

INTRODUCTION

Candida albicans is a commensal fungus that colonizes most healthy individuals' skin and mucosal surfaces but can also cause life-threatening invasive infections, particularly in immunocompromised patients. Despite antifungal treatment availability, drug resistance is increasing, and mortality rates remain unacceptably high. Heat shock protein Ssa1, a conserved member of the Hsp70 family in yeast, is a novel invasin that binds to host cell cadherins, induces host cell endocytosis, and enables C. albicans to cause maximal damage to host cells and induces disseminated and oropharyngeal disease.

RESULT

Here we discovered a mouse monoclonal antibody (mAb 13F4) that targeting C. albicans Ssa1 with high affinity (EC50 = 39.78 ng/mL). mAb 13F4 prevented C. albicans from adhering to and invading human epithelial cells, displayed antifungal activity, and synergized with fluconazole in proof of concept in vivo studies. mAb 13F4 significantly prolonged the survival rate of the hematogenous disseminated candidiasis mice to 75%. We constructed a mAb 13F4 three-dimensional structure using homology modeling methods and found that the antigen-binding fragment (Fab) interacts with the Ssa1 N-terminus.

DISCUSSION

These results suggest that blocking Ssa1 cell surface function may effectively control invasive C. albicans infections and provide a potential new treatment strategy for invasive fungal infections.

Discovery of BRD4-HDAC Dual Inhibitors with Improved Fungal Selectivity and Potent Synergistic Antifungal Activity against Fluconazole-Resistant Candida albicans

Over the past several decades, invasive fungal infections, especially candidiasis, have caused dramatic morbidity and mortality due to ineffective antifungal drugs and severe drug resistance. Herein, new BRD4-histone deacetylase (HDAC) inhibitors were designed to restore the susceptibility of Candida albicans (C. albicans) to fluconazole (FLC). Interestingly, several compounds showed excellent selectivity against fungal HDACs. In particular, compound B2 showed excellent synergistic effect with FLC against resistant C. albicans (FICI = 0.063) with high selectivity against fungal HDACs (SI = 1653) and low cytotoxicity. Compound B2 effectively synergized with FLC and prevented biofilm formation and morphological transition in resistant C. albicans, potentiating the antifungal activity of FLC in vivo and significantly reducing kidney fungal loads. Thus, this drug combination is promising in the treatment of resistant C. albicans infections.

Species-Selective Targeting of Fungal Hsp90: Design, Synthesis, and Evaluation of Novel 4,5-Diarylisoxazole Derivatives for the Combination Treatment of Azole-Resistant Candidiasis

Invasive fungal infections are emerging as serious infectious diseases worldwide. Because of the development of antifungal drug resistance, the limited efficacy of the existing drugs has led to high mortality in patients. The use of the essential eukaryotic chaperone Hsp90, which plays a multifaceted role in drug resistance across diverse pathogenic fungal species, is considered to be a new strategy to mitigate the resistance and counter the threat posed by drug-resistant fungi. Thus, a series of 4,5-diarylisoxazole analogues as fungal Hsp90 inhibitors were designed and synthesized that had potent synergistic effects with fluconazole in vitro and in vivo. In particular, compound A17 could avoid the potential mammalian toxicity of Hsp90 inhibitors based on key reside differences between humans and fungi. These data support the feasibility of targeting fungal Hsp90 as a promising antifungal strategy and further development of compound A17 as a valuable research probe for the investigation of fungal Hsp90.

Broadening antifungal spectrum and improving metabolic stablity based on a scaffold strategy: Design, synthesis, and evaluation of novel 4-phenyl-4,5-dihydrooxazole derivatives as potent fungistatic and fungicidal reagents

5-phenylthiophene derivatives exhibited excellent antifungal activity against Candida albicans, Candida tropicalis and Cryptococcus neoformans. However, optimal compound 7 was inactive against Aspergillus fumigatus and unstable in human liver microsomes in vitro with a half-life of 18.6 min. To discover antifungal agents with a broad spectrum and improve the metabolic properties of the compounds, the scaffold hopping strategy was adopted and a series of 4-phenyl-4,5-dihydrooxazole derivatives were designed and synthesized. It was especially encouraging that compound 22a displayed significant antifungal activities against eight susceptible strains and seven FLC-resistant strains. Furthermore, the potent compound 22a could prevent the formation of fungalbiofilms and displayed satisfactory fungicidal activity. In addition, the metabolic stability of compound 22a was improved significantly, with the half-life of 70.5 min. Compound 22a was almost nontoxic to mammalian A549, MCF-7, HepG2, and 293T cells. Moreover, pharmacokinetic studies in SD rats showed that compound 22a exhibited pharmacokinetic properties with a bioavailability of 15.22% and a half-life of 4.44 h, indicating that compound 22a is worthy of further study.

The Role of HMGB1 in Invasive Candida albicans Infection

INTRODUCTION

High mobility group box 1 (HMGB1) is an important "late" inflammatory mediator in bacterial sepsis. Ethyl pyruvate (EP), an inhibitor of HMGB1, can prevent bacterial sepsis by decreasing HMGB1 levels. However, the role of HMGB1 in fungal sepsis is still unclear. Therefore, we investigated the role of HMGB1 and EP in invasive C. albicans infection.

METHODS

We measured serum HMGB1 levels in patients with sepsis with C. albicans infection and without fungal infection, and control subjects. We collected clinical indices to estimate correlations between HMGB1 levels and disease severity. Furthermore, we experimentally stimulated mice with C. albicans and C. albicans + EP. Then, we examined HMGB1 levels from serum and tissue, investigated serum levels of tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6), determined pathological changes in tissues, and assessed mortality.

RESULTS

Serum HMGB1 levels in patients with severe sepsis with C. albicans infection were elevated. Increased HMGB1 levels were correlated with procalcitonin (PCT), C-reactive protein (CRP), 1,3-β-D-Glucan (BDG) and C. albicans sepsis severity. HMGB1 levels in serum and tissues were significantly increased within 7 days after mice were infected with C. albicans. The administration of EP inhibited HMGB1 levels, decreased tissue damage, increased survival rates and inhibited the release of TNF-α and IL-6.

CONCLUSIONS

HMGB1 levels were significantly increased in invasive C. albicans infections. EP prevented C. albicans lethality by decreasing HMGB1 expression and release. HMGB1 may provide an effective diagnostic and therapeutic target for invasive C. albicans infections.

Identification of Thiazoyl Guanidine Derivatives as Novel Antifungal Agents Inhibiting Ergosterol Biosynthesis for Treatment of Invasive Fungal Infections

Invasive fungal infections (IFIs) are fatal infections, but treatment options are limited. The clinical efficacies of existing drugs are unsatisfactory because of side effects, drug-drug interaction, unfavorable pharmacokinetic profiles, and emerging drug-resistant fungi. Therefore, the development of antifungal drugs with a new mechanism is an urgent issue. Herein, we report novel aryl guanidine antifungal agents, which inhibit a novel target enzyme in the ergosterol biosynthesis pathway. Structure-activity relationship development and property optimization by reducing lipophilicity led to the discovery of 6h, which showed potent antifungal activity against Aspergillus fumigatus in the presence of serum, improved metabolic stability, and PK properties. In the murine systemic A. fumigatus infection model, 6h exhibited antifungal efficacy equivalent to voriconazole (1e). Furthermore, owing to the inhibition of a novel target in the ergosterol biosynthesis pathway, 6h showed antifungal activity against azole-resistant A. fumigatus.

A Comparison of Candida Detection in Sputum by the Conventional Culture and Fluorescent Polymerase Chain Reaction Methods

Background

Candida is a pathogenic fungus. In recent years, the increase in immunosuppressive diseases has led to an increase in Candida infections, with the lungs being the most common site. Therefore, the aim of this study was to compare the positive detection rates of Candida in sputum samples by Candida culture and fluorescent polymerase chain reaction (PCR), and to explore a new method for rapid, accurate, and effective detection of Candida in sputum, providing swift evidence of clinical fungal infection.

Material/Methods

From October 2016 to March 2017, 300 sputum samples were collected and detected by the conventional culture method and fluorescent PCR method. The positive rate of Candida detection was compared between the 2 methods.

Results

In the 300 sputum samples, the positive detection rate of Candida was 50% by the culture method and 65.67% by the fluorescent PCR method (P<0.001). Therefore, the positive detection rate of Candida was higher by the fluorescent PCR method.

Conclusions

The conventional culture method for Candida needs a longer duration (24 h to 48 h) and the positive detection rate is low. However, it takes only 3 h to detect Candida in sputum by the fluorescent PCR method, the positive detection rate is high, and can be used as a screening method for Candida in sputum samples. Additional large-scale clinical trials need to be completed to assess the correlation between fluorescent PCR and pulmonary Candida infection.

Invasive fungal infections in a pediatric hematology-oncology department: A 16-year retrospective study

Background and Purpose

Invasive fungal infections (IFIs) are a major cause of morbidity and mortality in immunocompromised children. The purpose of our study was to evaluate the incidence of IFIs in pediatric patients with underlying hematologic malignancies and determine the patient characteristics, predisposing factors, diagnosis, treatment efficacy, and outcome of IFIs.

Materials and Methods

For the purpose of the study, a retrospective analysis was performed on cases with proven and probable fungal infections from January 2001 to December 2016 (16 years).

Results

During this period, 297 children with hematologic malignancies were admitted to the 2nd Pediatric Department of Aristotle University of Thessaloniki, Greece, and 24 cases of IFIs were registered. The most common underlying diseases were acute lymphoblastic leukemia (ALL; n=19,79%), followed by acute myeloid leukemia (AML; n=4, 17%) and non-Hodgkin lymphoma (NHL; n=1,4%). The crude incidence rates of IFIs in ALL, AML, and NHL were 10.5%, 18.2%, and 2.8% respectively. Based on the results, 25% (n=6) and 75% (n=18) of the patients were diagnosed as proven and probable IFI cases, respectively. The lung was the most common site of involvement in 16 (66.7%) cases. Furthermore, Aspergillus and Candida species represented 58.3% and 29.1% of the identified species, respectively. Regarding antifungal treatment, liposomal amphotericin B was the most commonly prescribed therapeutic agent (n=21), followed by voriconazole (n=9), caspofungin (n=3), posaconazole (n=3), micafungin (n=1), and fluconazole (n=1). In addition, 12 children received combined antifungal treatment. The crude mortality rate was obtained as 33.3%.

Conclusion

As the findings of the present study indicated, despite the progress in the diagnosis and treatment of IFIs with the use of new antifungal agents, the mortality rate of these infections still remains high.

Ibrexafungerp: An orally active β-1,3-glucan synthesis inhibitor

We previously reported medicinal chemistry efforts that identified MK-5204, an orally efficacious β-1,3-glucan synthesis inhibitor derived from the natural product enfumafungin. Further extensive optimization of the C2 triazole substituent identified 4-pyridyl as the preferred replacement for the carboxamide of MK-5204, leading to improvements in antifungal activity in the presence of serum, and increased oral exposure. Reoptimizing the aminoether at C3 in the presence of this newly discovered C2 substituent, confirmed that the (R) t-butyl, methyl aminoether of MK-5204 provided the best balance of these two key parameters, culminating in the discovery of ibrexafungerp, which is currently in phase III clinical trials. Ibrexafungerp displayed significantly improved oral efficacy in murine infection models, making it a superior candidate for clinical development as an oral treatment for Candida and Aspergillus infections.

Candidemia in a public hospital in Northeastern Brazil: Epidemiological features and risk factors in critically ill patients

BACKGROUND

Candidemia is a life-threatening fungal infection characterized by the presence of Candida in the blood.

AIMS

To describe the clinical-epidemiological features and main risk factors among patients with candidemia admitted to Intensive Care Unit.

METHODS

A cross-sectional, retrospective and observational study was performed between January 2015 and July 2016. Laboratory reports and medical records from ICU patients admitted to a public hospital in northeastern Brazil were analyzed.

RESULTS

There were 1573 admissions and 67 of them were positive for candidemia. The majority of patients were male (53.3%) and remained at the hospital for more than seven days (86.6%). Non-C. albicansCandida infections (60%) were predominant. Broad-spectrum antibiotic therapy was prescribed in 98.4% of the cases. The most frequent underlying diseases were sepsis (73.3%), presence of solid tumors (15%), respiratory condition (60%), urinary tract disease (56.6%) and gastrointestinal tract diseases (23.3%). Surgeries were carried out on 43% of the patients, consisting of 23.3% abdominal surgeries, with a mortality rate of 92.8%. Risk factors were venous central access (93.3%), mechanical ventilation (81.6%), nasoenteral tube (83.3%), nasogastric tube (25%), indwelling bladder catheter (88.3%), diabetes mellitus (55%) and tracheostomy (36.6%). Statistical analysis correlated the use of indwelling bladder catheter with a higher mortality rate (r=0.07412, p=0.0353).

CONCLUSIONS

The current study reveals the high case fatality rates among critically ill patients suffering from candidemia admitted to ICU. Herein, we highlight the importance of identifying non-C. albicansCandida species and reinforce the idea of carrying out epidemiological surveillances and antifungal susceptibility tests.

Invasive candidiasis and candidemia in pediatric and neonatal patients: A review of current guidelines

Several international and national guidelines have been proposed for the treatment and prevention of invasive candidiasis/candidemia (IC/C) in both neonatal and pediatric patients. This article is a review of the current guidelines, recommendations, and expert panel consensus of a number of associations and conferences on the prevention and management of IC and candidemia in both pediatric and neonatal patients. The investigated resources included the Infectious Diseases Society of America, the European Conference on Infection in Leukaemia, the European Society of Clinical Microbiology and Infectious Diseases, the German Speaking Mycological Society/Paul-Ehrlich Society for Chemotherapy, as well as the Canadian, Middle Eastern, and Australian guidelines. Echinocandins and liposomal amphotericin B (L-AmB) are the first-line agents in the treatment of IC and candidemia both for immunocompetent and immunocompromised pediatric patients. The recommendations suggested to keep patients under sterile conditions for at least 14 days after blood cultures as the prompt initiation of antifungal treatment. Guidelines addressing the neonates recommended to use L-AmB, deoxycholate AmB (D-AmB), and fluconazole based on three main principles of no previous exposure to azoles, the prompt initiation of antifungal treatment, and control of predisposing underlying conditions. Despite minor differences among the investigated guidelines, general treatment recommendations suggest the prompt initiation of antifungal treatment and control of all predisposing underlying conditions.

Evaluation of Candida species and antifungal susceptibilities among children with invasive candidiasis

AIM

Non-albicans Candida species and resistant microorganisms have been more commonly isolated in invasive candidiasis in recent years. The aim of this study was to evaluate the distrubution of Candida spp and antifungal resistance in our clinic.

MATERIAL AND METHODS

Fifty-four Candida isolates and antifungal susceptibility results obtained from patients diagnosed as having invasive candidiasis between December 2012 and June 2016 were included. Clinical and laboratory data were retrospectively analyzed. E-test method was used in order to determine antifungal susceptibilities of Candida spp for amphotericin B, fluconazole, voriconazole, ketoconazole, itraconazole, anidulafungin, caspofungin, and flucytosine.

RESULTS

The clinical diagnoses of the patients were candidemia (n=27, 50%), catheter-related blood stream infection (n=1, 1.8%), urinary tract infection (n=13, 24%), surgical site infection (n=4, 7.4%), intraabdominal infection (n=3, 5.5%), empyema (n=2, 3.7%), and pneumonia (n=4, 7.4%). The most common isolated agent was C. albicans (n=27, 50%) and the others were C. parapsilosis (n=13, 24%), C. tropicalis (n=6, 11.1%), C. glabrata (n=3, 5.6%), C. lusitaniae (n=2, 3.7%), and unspecified Candida spp. (n=3, 5.6%). Fluconazole resistance was 7.4% among all isolates. Resistance against itraconazole, ketoconazole, anidulafungin, voriconazole and caspofungin were 33.3%, 12.5%, 11.1%, 5%, and 2.5%, respectively. Isolates presented intermediate resistance against itraconazole (41.7%), voriconazole (5.6%), and amphotericin B (3.7%) to varying extents. All of the isolates were susceptible to flucytosine.

CONCLUSIONS

In our clinic, C. albicans and non-albicans Candida species were equally distributed and antifungal susceptibilities against major antifungal agents such as fluconazole, amphotericin B, and caspofungin were found considerably high.

Exploring the thiazole scaffold for the identification of new agents for the treatment of fluconazole resistant Candida

Cyclohexyliden- and 2-methylcyclohexyliden-hydrazo-4-arylthiazoles were synthesized and tested as antifungal agents. All compounds exhibited minimal inhibitory concentration (MIC) values comparable with those of fluconazole (FLC). Moreover, some compounds showed fungicidal activity at low concentration. Worth noting five out of nine compounds were active towards Candida albicans 25 FLC resistant isolated from clinical specimens. The cellular toxicity was evaluated and none of the compounds is toxic at the MIC. On the basis of our data we can conclude that these derivatives are promising agents for the treatment of resistant C. albicans.

Evaluation of paper gradient concentration strips for antifungal combination testing of Candida spp

In vitro combination testing with broth microdilution chequerboard (CHEQ) method is widely used although it is time-consuming, cumbersome and difficult to apply in routine setting of clinical microbiology laboratory. A new gradient concentration paper strip method, the Liofilchem(®) MIC test strips (MTS), provides an alternative easy and fast method enabling the simultaneous diffusion of both drugs in combination. We therefore tested a polyene+azole and an azole+echinocandin combination against 18 Candida isolates with the CHEQ method based on EUCAST guidelines and the MTS method in research and routine settings. Fractional inhibitory concentration (FIC) indices were calculated after 24 and 48 h of incubation based on complete and prominent (FIC-2) growth inhibition endpoints. Reproducibility and agreement within 1 twofold dilution was assessed. The FICs of the two methods were correlated quantitatively with t-test and Pearson analysis and qualitatively with Chi-squared test. The reproducibility of the CHEQ and MTS method was 88-100% and their agreement was 80% with 62-77% of MTS FICs being higher than the corresponding CHEQ FICs. A statistically significant Pearson correlation (r = 0.86, P = 0.0003) and association (χ(2) = 17.05, df = 4, P = 0.002) was found between MTS FIC and CHEQ FIC-2 after 24 h. Categorical agreement was 63% with no very major or major errors. All MTS synergistic interactions were also synergistic with the CHEQ method.

How to treat fungal infections in ICU patients

Fungal infections represent a major burden in the critical care setting with increasing morbidity and mortality. Candidiasis is the leading cause of such infections, with C. albicans being the most common causative agent, followed by Aspergillosis and Mucormycosis. The diagnosis of such infections is cumbersome requiring increased clinical vigilance and extensive laboratory testing, including radiology, cultures, biopsies and other indirect methods. However, it is not uncommon for definitive evidence to be unavailable. Risk and host factors indicating the probability of infections may greatly help in the diagnostic approach. Timely and adequate intervention is important for their successful treatment. The available therapeutic armamentarium, although not very extensive, is effective with low resistance rates for the newer antifungal agents. However, timely and prudent use is necessary to maximize favorable outcomes.

Invasive candidiasis in critical care setting, updated recommendations from “Invasive Fungal Infections-Clinical Forum”, Iran

Invasive candidiasis (IC) bears a high risk of morbidity and mortality in the intensive care units (ICU). With the current advances in critical care and the use of wide-spectrum antibiotics, invasive fungal infections (IFIs) and IC in particular, have turned into a growing concern in the ICU. Further to blood cultures, some auxiliary laboratory tests and biomarkers are developed to enable an earlier detection of infection, however these test are neither consistently available nor validated in our setting. On the other hand, patients’ clinical status and local epidemiology data may justify the empiric antifungal approach using the proper antifungal option. The clinical approach to the management of IC in febrile, non-neutropenic critically ill patients has been defined in available international guidelines; nevertheless such recommendations need to be customized when applied to our local practice. Over the past three years, Iranian experts from intensive care and infectious diseases disciplines have tried to draw a consensus on the management of IFI with a particular focus on IC in the ICU. The established IFI-clinical forum (IFI-CF), comprising the scientific leaders in the field, has recently come up with and updated recommendation on the same (June 2014). The purpose of this review is to put together literature insights and Iranian experts’ opinion at the IFI-CF, to propose an updated practical overview on recommended approaches for the management of IC in the ICU.

Invasive candidiasis and candidaemia in neonates and children: update on current guidelines

Invasive candidiasis (IC) and candidaemia are leading causes of infectious morbidity and mortality among immunocompromised paediatric patients and those admitted to intensive care units. Despite improvements in diagnosis, prevention and treatment, both mortality rates and the economic burden of disease still remain high. To address this issue, several international societies and organisations have proposed guidelines for the management of IC/candidaemia in both neonates and children. In this article, we review current recommendations of the Infectious Diseases Society of America, the European Conference on Infection in Leukaemia, the European Society of Clinical Microbiology and Infectious Diseases and the German Speaking Mycological Society/Paul-Ehrlich Society for Chemotherapy for the management and prevention of IC/candidaemia in children and neonates.

Invasive fungal infections in the ICU: how to approach, how to treat

Invasive fungal infections are a growing problem in critically ill patients and are associated with increased morbidity and mortality. Most of them are due to Candida species, especially Candida albicans. Invasive candidiasis includes candidaemia, disseminated candidiasis with deep organ involvement and chronic disseminated candidiasis. During the last decades rare pathogenic fungi, such as Aspergillus species, Zygomycetes, Fusarium species and Scedosporium have also emerged. Timely diagnosis and proper treatment are of paramount importance for a favorable outcome. Besides blood cultures, several laboratory tests have been developed in the hope of facilitating an earlier detection of infection. The antifungal armamentarium has also been expanded allowing a treatment choice tailored to individual patients' needs. The physician can choose among the old class of polyenes, the older and newer azoles and the echinocandins. Factors related to patient's clinical situation and present co-morbidities, local epidemiology data and purpose of treatment (prophylactic, pre-emptive, empiric or definitive) should be taken into account for the appropriate choice of antifungal agent.