Assessing risk factors for systemic fungal infections

The atypical antipsychotic aripiprazole alters the outcome of disseminated Candida albicans infections

Invasive fungal infections impose an enormous clinical, social, and economic burden on humankind. One of the most common species responsible for invasive fungal infections is Candida albicans. More than 30% of patients with disseminated candidiasis fail therapy with existing antifungal drugs, including the widely used azole class. We previously identified a collection of 13 medications that antagonize the activity of the azoles on C. albicans. Although gain-of-function mutations responsible for antifungal resistance are often associated with reduced fitness and virulence, it is currently unknown how exposure to azole antagonistic drugs impacts C. albicans physiology, fitness, or virulence. In this study, we examined how exposure to seven azole antagonists affects C. albicans phenotype and capacity to cause disease. Most of the azole antagonists appear to have little impact on fungal growth, morphology, stress tolerance, or gene transcription. However, aripiprazole had a modest impact on C. albicans hyphal growth and increased cell wall chitin content. It also aggravated the disseminated C. albicans infections in mice. This effect was abrogated in immunosuppressed mice, indicating that it is at least in part dependent upon host immune responses. Collectively, these data provide proof of principle that unanticipated drug-fungus interactions have the potential to influence the incidence and outcomes of invasive fungal disease.

Humans vs. Fungi: An Overview of Fungal Pathogens against Humans

Human fungal diseases are infections caused by any fungus that invades human tissues, causing superficial, subcutaneous, or systemic diseases. Fungal infections that enter various human tissues and organs pose a significant threat to millions of individuals with weakened immune systems globally. Over recent decades, the reported cases of invasive fungal infections have increased substantially and research progress in this field has also been rapidly boosted. This review provides a comprehensive list of human fungal pathogens extracted from over 850 recent case reports, and a summary of the relevant disease conditions and their origins. Details of 281 human fungal pathogens belonging to 12 classes and 104 genera in the divisions ascomycota, basidiomycota, entomophthoromycota, and mucoromycota are listed. Among these, Aspergillus stands out as the genus with the greatest potential of infecting humans, comprising 16 species known to infect humans. Additionally, three other genera, Curvularia, Exophiala, and Trichophyton, are recognized as significant genera, each comprising 10 or more known human pathogenic species. A phylogenetic analysis based on partial sequences of the 28S nrRNA gene (LSU) of human fungal pathogens was performed to show their phylogenetic relationships and clarify their taxonomies. In addition, this review summarizes the recent advancements in fungal disease diagnosis and therapeutics.

The atypical antipsychotic aripiprazole alters the outcome of disseminated Candida albicans infections

Invasive fungal infections (IFIs) impose an enormous clinical, social, and economic burden on humankind. For many IFIs, ≥ 30% of patients fail therapy with existing antifungal drugs, including the widely used azole class. We previously identified a collection of 13 approved medications that antagonize azole activity. While gain-of-function mutants resulting in antifungal resistance are often associated with reduced fitness and virulence, it is currently unknown how exposure to azole antagonistic drugs impact C. albicans physiology, fitness, or virulence. In this study, we examined how exposure to azole antagonists affected C. albicans phenotype and capacity to cause disease. We discovered that most of the azole antagonists had little impact on fungal growth, morphology, stress tolerance, or gene transcription. However, aripiprazole had a modest impact on C. albicans hyphal growth and increased cell wall chitin content. It also worsened the outcome of disseminated infections in mice at human equivalent concentrations. This effect was abrogated in immunosuppressed mice, indicating an additional impact of aripiprazole on host immunity. Collectively, these data provide proof-of-principle that unanticipated drug-fungus interactions have the potential to influence the incidence and outcomes of invasive fungal disease.

Infective complications of cosmetic tourism: A systematic literature review

BACKGROUND

Cosmetic tourism has increased dramatically over the years. We performed a systematic review of the literature to find reports of infective complications following cosmetic surgery, focusing on epidemiology, clinical, and surgical management. In addition, we identified cosmetic tourism trends in terms of mobilization from the country of origin and travel destinations.

METHODS

A search on PubMed, Embase, and Web of Science was performed between March and August 2022. The search was not restricted based on study date. Only English manuscripts were assessed. Reviews, short communications, letters, and correspondences were excluded after reviewing their references for potentially relevant studies. Articles related to non-cosmetic surgeries were also excluded from the study.

RESULTS

We identified 152 articles, of which 31 were duplicates and 47 were excluded based on title/abstract assessment. Three non-English manuscripts, 13 reviews, 12 letters to the editor, and 10 articles that did not feature clinical cases were also rejected. Thirty-six articles were included for analysis. We found 370 patients with infective complications following cosmetic surgery. The severity of complications was stratified according to the Clavien-Dindo classification. Most reports were from the United States (56.5%), followed by Switzerland and the United Kingdom. Travel destinations included the Dominican Republic (34.3%), Turkey, and Colombia.

CONCLUSION

Infective complications commonly occurred after abdominoplasties in patients who underwent cosmetic surgeries in Latin America or Asia. Most infective complications required management with surgical procedures that involved the administration of local, regional, or general anesthesia. Gluteal augmentations were the fourth most common cosmetic procedures; however, they were associated with the highest number of severe cases, which required intensive care treatment.

Burden of fungal infections in Kenya

The burden of fungal infections has been on the rise globally and remains a significant public health concern in Kenya. We estimated the incidence and prevalence of fungal infections using all mycology publications in Kenya up to January 2023, and from neighbouring countries where data lacked. We used deterministic modelling using populations at risk to calculate the disease burden. The total burden of serious fungal infections is estimated to affect 6,328,294 persons which translates to 11.57% of the Kenyan population. Those suffering from chronic infections such as chronic pulmonary aspergillosis are estimated to be 100,570 people (0.2% of the population) and probably nearly 200,000 with fungal asthma, all treatable with oral antifungal therapy. Serious acute fungal infections secondary to HIV (cryptococcal meningitis, disseminated histoplasmosis, pneumocystis pneumonia, and mucosal candidiasis) affect 196,543 adults and children (0.4% of the total population), while cancer-related invasive fungal infection cases probably exceed 2,299 and those in intensive care about 1,230 incident cases, including Candida auris bloodstream infection. The burden of fungal infections in Kenya is high; however, limited diagnostic test availability, low clinician awareness and inadequate laboratory capacity constrain the country's health system in responding to the syndemic of fungal disease in Kenya.

"Under Pressure" - How fungi evade, exploit, and modulate cells of the innate immune system

The human immune system uses an arsenal of effector mechanisms to prevent and counteract infections. Yet, some fungal species are extremely successful as human pathogens, which can be attributed to a wide variety of strategies by which these fungi evade, exploit, and modulate the immune system. These fungal pathogens normally are either harmless commensals or environmental fungi. In this review we discuss how commensalism, but also life in an environmental niche without human contact, can drive the evolution of diverse and specialized immune evasion mechanisms. Correspondingly, we discuss the mechanisms contributing to the ability of these fungi to cause superficial to life-threatening infections.

European Hedgehogs (Erinaceus europaeus L.) as a Reservoir of Dermatophytes in Poland

The European hedgehog (Erinaceus europaeus Linnaeus) frequently colonises areas located close to human life in cities, as these are more suitable nest sites offering an abundance of food and allowing avoidance of predators. However, urbanisation has a significant impact on the epidemiology of infectious diseases, including dermatophytoses, the primary source of which are wild animals. In this study, we determined the spectrum of dermatophytes isolated from the European hedgehog and assessed their susceptibility profile to antifungal drugs. Symptomatic and asymptomatic dermatophyte infections were observed in 7.7% and 8% of the 182 examined free-living hedgehogs, respectively. In the pool of the isolated dermatophyte strains, Trichophyton erinacei was dominant (29.9%), followed by Trichophyton mentagrophytes (17.9%), Trichophyton benhamiae (13.4%), Nannizzia gypsea (11.9%), Microsporum canis (10.4%), Nannizzia nana (7.5%), Paraphyton cookei (6.0%), and Nannizzia fulva (3.0%). Susceptibility tests revealed the highest activity of luliconazole and the lowest of activity fluconazole among the azole drugs applied. Although terbinafine generally exhibited high efficacy, two Trichophyton mentagrophytes isolates showed resistance to this drug (MIC = 2 µg/ml) resulting from missense mutations in the SQLE gene corresponding to the amino acid substitution Leu393Phe. Summarising, our study has also revealed that such wildlife animals as hedgehogs can be a reservoir of pathogenic human dermatophytes, including harmful strains resistant to commonly used antifungal drugs.

Periprosthetic Joint Infections Caused by Candida Species—A Single-Center Experience and Systematic Review of the Literature

Background: The aim of this study was to analyze the treatment results of fungal periprosthetic joint infections (PJI) caused by Candida species from a single orthopedic center and to compare them with reports from other institutions. Methods: Eight patients operated on from January 2014 to December 2021 met the inclusion criteria and were analyzed in terms of clinical outcomes. A systematic review of the literature identified 153 patients with Candida PJIs extracted from 12 studies according to the PRISMA (Preferred Reporting Item for Systematic Reviews and Meta-Analyses) guidelines. Results: The success rate of the treatment in the case series was 50%. The most frequent pathogens were Candida albicans (three cases; 37.5%) and Candida parapsilosis (three cases; 37.5%). In one patient (12.5%), bacterial co-infection was noted, and in five patients (62.5%) significant risk factors of PJI were confirmed. The overall success rate on the basis of data collected for systematic review was 65.5%. A sub-analysis of 127 patients revealed statistically significant differences (p = 0.02) with a higher success rate for the knees (77.6%) than for the hips (58%). In 10 studies the analysis of risk factors was performed and among 106 patients in 77 (72.6%) comorbidities predispose to fungal PJI were confirmed. Bacterial co-infection was noted in 84 patients (54.9%). In 93 patients (60.7%) Candida albicans was the culprit pathogen, and in 39 patients (25.5%) Candida parapsilosis was the culprit pathogen. Based on these two most frequent Candida species causing PJI, the success rate of the treatment was statistically different (p = 0.03), and was 60.3% and 83.3%, respectively. The two-stage strategy was more favorable for patients with Candida parapsilosis infections (94.4% success rate) than the one-stage protocol (50% success rate; p = 0.02); as well as in comparison to the two-stage treatment of Candida albicans (65% success rate; p = 0.04). Conclusions: The analysis of the literature showed no differences in the overall success rate between one- and two-stage surgical strategies for all Candida species, but differed significantly comparing the two most frequent strains and concerning PJI localization. The frequent presence of bacterial co-infections makes it necessary to consider the additional administration of antibiotics in the case of fungal PJI.

Identification of Inhibitors of Fungal Fatty Acid Biosynthesis

Fungal fatty acid (FA) synthase and desaturase enzymes are essential for the growth and virulence of human fungal pathogens. These enzymes are structurally distinct from their mammalian counterparts, making them attractive targets for antifungal development. However, there has been little progress in identifying chemotypes that target fungal FA biosynthesis. To accomplish this, we applied a whole-cell-based method known as Target Abundance-based FItness Screening using Candida albicans. Strains with varying levels of FA synthase or desaturase expression were grown in competition to screen a custom small-molecule library. Hit compounds were defined as preferentially inhibiting the growth of the low target-expressing strains. Dose-response experiments confirmed that 16 hits (11 with an acyl hydrazide core) differentially inhibited the growth of strains with an altered desaturase expression, indicating a specific chemical-target interaction. Exogenous unsaturated FAs restored C. albicans growth in the presence of inhibitory concentrations of the most potent acyl hydrazides, further supporting the primary mechanism being inhibition of FA desaturase. A systematic analysis of the structure-activity relationship confirmed the acyl hydrazide core as essential for inhibitory activity. This collection demonstrated broad-spectrum activity against Candida auris and mucormycetes and retained the activity against azole-resistant candida isolates. Finally, a preliminary analysis of toxicity to mammalian cells identified potential lead compounds with desirable selectivities. Collectively, these results establish a scaffold that targets fungal FA biosynthesis with a potential for development into novel therapeutics.

Synthesis of fish scale derived hydroxyapatite silica propyl bis aminoethoxy ethane cuprous complex (HASPBAEECC) as a novel hybrid nano-catalyst for highly efficient synthesis of new benzimidazole-1,2,3-triazole hybrid analogues as antifungal agents

The preparation, characterization and application of hydroxyapatite silica propyl bis aminoethoxy ethane cuprous complex (HASPBAEECC) as a novel hybrid nano-catalyst for synthesis of new benzimidazole-1,2,3-triazole hybrid analogues as promising antifungal agents have been described. HASPBAEECC is fully characterized by different microscopic, spectroscopic and physical techniques, including scanning electron microscopy (SEM), transmission, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA) and FT-IR. The 'Click̕ Huisgen cycloaddition reaction of N-propargyl benzimidazole with diverse azidoalkyls in a THF-water media at ambient temperature provides the products in good-to-excellent yields using HASPBAEECC. HASPBAEECC is proved to be a stable, low cost, reusable and environmentally benign nanohybrid catalyst. The target compounds were screened against some pathogenic fungal comprising Candida albicans, Candida krusei, Candida parapsilosis, Aspergillus fumigatus and Aspergillus flavus in which it was determined that compounds 11f and 11 h have displayed promising antifungal activity similar to fluconazole as a reference drug. HASPBAEECC is a novel hybrid nano-catalyst for highly efficient synthesis of new benzimidazole-1,2,3- triazole hybrid analogues as antifungal agents.

Structural Insights into the Azole Resistance of the Candida albicans Darlington Strain Using Saccharomyces cerevisiae Lanosterol 14α-Demethylase as a Surrogate

Target-based azole resistance in Candida albicans involves overexpression of the ERG11 gene encoding lanosterol 14α-demethylase (LDM), and/or the presence of single or multiple mutations in this enzyme. Overexpression of Candida albicans LDM (CaLDM) Y132H I471T by the Darlington strain strongly increased resistance to the short-tailed azoles fluconazole and voriconazole, and weakly increased resistance to the longer-tailed azoles VT-1161, itraconazole and posaconazole. We have used, as surrogates, structurally aligned mutations in recombinant hexahistidine-tagged full-length Saccharomyces cerevisiae LDM6×His (ScLDM6×His) to elucidate how differential susceptibility to azole drugs is conferred by LDM of the C. albicans Darlington strain. The mutations Y140H and I471T were introduced, either alone or in combination, into ScLDM6×His via overexpression of the recombinant enzyme from the PDR5 locus of an azole hypersensitive strain of S. cerevisiae. Phenotypes and high-resolution X-ray crystal structures were determined for the surrogate enzymes in complex with representative short-tailed (voriconazole) and long-tailed (itraconazole) triazoles. The preferential high-level resistance to short-tailed azoles conferred by the ScLDM Y140H I471T mutant required both mutations, despite the I471T mutation conferring only a slight increase in resistance. Crystal structures did not detect changes in the position/tilt of the heme co-factor of wild-type ScLDM, I471T and Y140H single mutants, or the Y140H I471T double-mutant. The mutant threonine sidechain in the Darlington strain CaLDM perturbs the environment of the neighboring C-helix, affects the electronic environment of the heme, and may, via differences in closure of the neck of the substrate entry channel, increase preferential competition between lanosterol and short-tailed azole drugs.

Reinforcing the Immunocompromised Host Defense against Fungi: Progress beyond the Current State of the Art

Despite the availability of a variety of antifungal drugs, opportunistic fungal infections still remain life-threatening for immunocompromised patients, such as those undergoing allogeneic hematopoietic cell transplantation or solid organ transplantation. Suboptimal efficacy, toxicity, development of resistant variants and recurrent episodes are limitations associated with current antifungal drug therapy. Adjunctive immunotherapies reinforcing the host defense against fungi and aiding in clearance of opportunistic pathogens are continuously gaining ground in this battle. Here, we review alternative approaches for the management of fungal infections going beyond the state of the art and placing an emphasis on fungus-specific T cell immunotherapy. Harnessing the power of T cells in the form of adoptive immunotherapy represents the strenuous protagonist of the current immunotherapeutic approaches towards combating invasive fungal infections. The progress that has been made over the last years in this field and remaining challenges as well, will be discussed.

Serious fungal disease incidence and prevalence in Indonesia

BACKGROUND

Indonesia is a tropical country, warm and humid, with numerous environmental fungi. Data on fungal disease burden help policymakers and clinicians.

OBJECTIVES

We have estimated the incidence and prevalence of serious fungal diseases.

METHODS

We found all published and unpublished data and estimated the incidence and prevalence of fungal diseases based on populations at risk. HIV data were derived from UNAIDS (2017), pulmonary tuberculosis (PTB) data from 2013-2019, data on chronic pulmonary aspergillosis (CPA) were used to estimate CPA prevalence and likely deaths, COPD data from Hammond (2020), lung cancer incidence was from Globocan 2018, and fungal rhinosinusitis was estimated using community data from India.

RESULTS

Overall ~7.7 million Indonesians (2.89%) have a serious fungal infection each year. The annual incidence of cryptococcosis in AIDS was 7,540. Pneumocystis pneumonia incidence was estimated at 15,400 in HIV and an equal number in non-HIV patients. An estimated 1% and 0.2% of new AIDS patients have disseminated histoplasmosis or Talaromyces marneffei infection. The incidence of candidaemia is 26,710. The annual incidence of invasive aspergillosis was estimated at 49,500 and the prevalence of CPA is at 378,700 cases. Allergic bronchopulmonary aspergillosis prevalence in adults is estimated at 336,200, severe asthma with fungal sensitisation at 443,800, and fungal rhinosinusitis at 294,000. Recurrent vulvovaginal candidiasis is estimated at 5 million/year (15-50 years old). The incidence of fungal keratitis around 40,050. Tinea capitis prevalence in schoolchildren about 729,000.

CONCLUSIONS

Indonesia has a high burden of fungal infections.

Aspergillosis, Avian Species and the One Health Perspective: The Possible Importance of Birds in Azole Resistance

The One Health context considers health based on three pillars: humans, animals, and environment. This approach is a strong ally in the surveillance of infectious diseases and in the development of prevention strategies. Aspergillus spp. are fungi that fit substantially in this context, in view of their ubiquity, as well as their importance as plant pathogens, and potentially fatal pathogens for, particularly, humans and avian species. In addition, the emergence of azole resistance, mainly in Aspergillus fumigatus sensu stricto, and the proven role of fungicides widely used on crops, reinforces the need for a multidisciplinary approach to this problem. Avian species are involved in short and long distance travel between different types of landscapes, such as agricultural fields, natural environments and urban environments. Thus, birds can play an important role in the dispersion of Aspergillus, and of special concern, azole-resistant strains. In addition, some bird species are particularly susceptible to aspergillosis. Therefore, avian aspergillosis could be considered as an environmental health indicator. In this review, aspergillosis in humans and birds will be discussed, with focus on the presence of Aspergillus in the environment. We will relate these issues with the emergence of azole resistance on Aspergillus. These topics will be therefore considered and reviewed from the “One Health” perspective.

Antifungal Agents in Agriculture: Friends and Foes of Public Health

Fungal diseases have been underestimated worldwide but constitute a substantial threat to several plant and animal species as well as to public health. The increase in the global population has entailed an increase in the demand for agriculture in recent decades. Accordingly, there has been worldwide pressure to find means to improve the quality and productivity of agricultural crops. Antifungal agents have been widely used as an alternative for managing fungal diseases affecting several crops. However, the unregulated use of antifungals can jeopardize public health. Application of fungicides in agriculture should be under strict regulation to ensure the toxicological safety of commercialized foods. This review discusses the use of antifungals in agriculture worldwide, the need to develop new antifungals, and improvement of regulations regarding antifungal use.

Fungal Infections with Ibrutinib and Other Small-Molecule Kinase Inhibitors

Purpose of review

Small molecule kinase inhibitors (SMKIs) have revolutionized the management of malignant and autoimmune disorders. Emerging clinical reports point toward an increased risk for invasive fungal infections (IFIs) in patients treated with certain SMKIs. In this mini-review, we highlight representative examples of SMKIs that have been associated with or are expected to give rise to IFIs.

Recent findings

The clinical use of the Bruton's tyrosine kinase inhibitor ibrutinib as well as other FDA-approved SMKIs has been associated with IFIs. The fungal infection susceptibility associated with the clinical use of certain SMKIs underscores their detrimental effects on innate and adaptive antifungal immune responses.

Summary

The unprecedented development and clinical use of SMKIs is expected to give rise to an expansion of iatrogenic immunosuppressive factors predisposing to IFIs (and other opportunistic infections). Beyond increased clinical surveillance, better understanding of the pathogenesis of SMKI-associated immune dysregulation should help devising improved risk stratification and prophylaxis strategies in vulnerable patients.

A Systematic Screen Reveals a Diverse Collection of Medications That Induce Antifungal Resistance in Candida Species

The increasing incidence of and high mortality rates associated with invasive fungal infections (IFIs) impose an enormous clinical, social, and economic burden on humankind. In addition to microbiological resistance to existing antifungal drugs, the large number of unexplained treatment failures is a serious concern. Due to the extremely limited therapeutic options available, it is critical to identify and understand the various causes of treatment failure if patient outcomes are to improve. In this study, we examined one potential source of treatment failure: antagonistic drug interactions. Using a simple screen, we systematically identified currently approved medications that undermine the antifungal activity of three major antifungal drugs-fluconazole, caspofungin, and amphotericin B-on four prevalent human fungal pathogens-Candida albicans, Candida glabrata, Candida parapsilosis, and Candida tropicalis This revealed that a diverse collection of structurally distinct drugs exhibit antagonistic interactions with fluconazole. Several antagonistic agents selected for follow-up studies induce azole resistance through a mechanism that depends on Tac1p/Pdr1p zinc-cluster transcription factors, which activate the expression of drug efflux pumps belonging to the ABC-type transporter family. Few antagonistic interactions were identified with caspofungin or amphotericin B, possibly reflecting their cell surface mode of action that should not be affected by drug efflux mechanisms. Given that patients at greatest risk of IFIs usually receive a multitude of drugs to treat various underlying conditions, these studies suggest that chemically inducible azole resistance may be much more common and important than previously realized.

Infection-Induced Kidney Diseases

Infection induced kidney diseases are of concern for clinicians because timely detection and treatment of infections may cure or limit the extent of injury inflicted by microorganisms causing the infections. Infections can cause kidney injury by either direct invasion, or indirectly by immune mediated mechanisms, which manifest as post-infectious glomerulonephritis, or infection-related glomerulonephritis. Clinical manifestations may be acute or chronic depending on the microorganisms, endemic/epidemic nature and source of infection. All microbials virus, bacteria, mycobacteria, fungus, and protozoa have been implicated in kidney diseases either causing direct kidney injuries or immune-mediated injuries. Infection control practices in large parts of world is limited by poverty, social behavior, high population density, deforestation, inadequate access to safe drinking water, and poor health care facilities. Although, antimicrobials and vaccinations have successfully eradicated and cured many infectious diseases; however injudicious antimicrobial use and emergence of resistant organisms complicated the disease severity like secondary renal amyloidosis with chronic persistent infection. Re-emergence of various infections has been a recent pattern in developed world leading to uncertain diagnostic challenges, and association with kidney diseases.

Prevalence of vulvovaginal candidiasis in gynecological practices in Germany: A retrospective study of 954,186 patients

Background and Purpose:

To the best of our knowledge, no information is available regarding the treatment of vulvovaginal candidiasis in gynecological practices. The goal of this study was to analyze the prevalence of vulvovaginal candidiasis (VVC) and the drugs prescribed for the treatment of this condition in women followed in gynecological practices in Germany.

Materials and Methods:

All the women followed in 262 gynecological practices between November 2014 and October 2016 were included in this study. The first outcome was the prevalence of patients diagnosed with VVC during this period. The second outcome was the prevalence of women with VVC who received an appropriate vaginal or systemic antimycotic prescription within 30 days after their first VVC diagnosis. Covariables included the use of gynecological/systemic antibiotics, consumption of oral/vaginal contraceptives, cancer, pregnancy, diabetes, and psychiatric diseases including depression, anxiety, and adjustment and somatoform disorders.

Results:

Between 2014 and 2016, 954,186 women were followed in gynecological practices, and 50,279 (5.3%) women were diagnosed with VVC during the same period. The use of gynecological antibiotics (OR=2.88), systemic antibiotics (OR=1.45), oral contraceptives (OR=1.74), and vaginal contraceptives (OR=1.84) were associated with an increase in the risk of VVC diagnosis. Cancer (OR=1.20) and pregnancy (OR=1.59) were additional risk factors. Approximately 75% of women diagnosed with VVC received an antimycotic prescription. The three most frequently prescribed drugs were clotrimazole (72%), fluconazole (14%), and nystatin (6%).

Conclusion:

More than 5% of women were diagnosed with VVC and the majority of them received an appropriate prescription.

The Goldilocks model of immune symbiosis with Mycobacteria and Candida colonizers

Mycobacteria and Candida species include significant human pathogens that can cause localized or disseminated infections. Although these organisms may appear to have little in common, several shared pathways of immune recognition and response are important for both control and infection-related pathology. In this article, we compare and contrast the innate and adaptive components of the immune system that pertain to these infections in humans and animal models. We also explore a relatively new concept in the mycobacterial field: biological commensalism. Similar to the well-established model of Candida infection, Mycobacteria species colonize their human hosts in equilibrium with the immune response. Perturbations in the immune response permit the progression to pathologic disease at the expense of the host. Understanding the immune factors required to maintain commensalism may aid with the development of diagnostic and treatment strategies for both categories of pathogens.

Efficacy, safety and feasibility of antifungal prophylaxis with posaconazole tablet in paediatric patients after haematopoietic stem cell transplantation

PURPOSE

Paediatric recipients of haematopoietic stem cell transplantation (HSCT) have a high risk for invasive fungal infections. Posaconazole oral suspension has proven to be effective in antifungal prophylaxis in adult and paediatric patients. A new posaconazole tablet formulation with absorption independent of the gastric conditions was approved by the FDA in 2013. This is the first report on the use of posaconazole tablets in paediatric patients.

METHODS

This single-centre study included 63 paediatric patients with haemato-oncological malignancies who received posaconazole for antifungal prophylaxis after HSCT. They were analysed for efficacy, feasibility and the safety of posaconazole. Out of 63 patients, 31 received posaconazole oral suspension and 32 received posaconazole tablets up to 200 days after transplantation. Analyses of the posaconazole trough levels were determined.

RESULTS

No possible, probable or proven invasive fungal infection was observed in either group. Posaconazole trough levels were significantly higher in the tablet group than in the suspension group at all analysed time points. Drug-related adverse events were similarly low in both groups.

CONCLUSIONS

Posaconazole tablets are effective in preventing invasive fungal infections in paediatric patients. As early as day 3 after starting posaconazole tablets, over 50% of the posaconazole trough levels were >500 ng/mL, while this was observed on day 14 after start with posaconazole suspension. The administration of posaconazole tablets was safe, effective and feasible as antifungal prophylaxis in paediatric patients after HSCT.

Antifungal Activity of the Ethanol Extract from Flos Rosae Chinensis with Activity against Fluconazole-Resistant Clinical Candida

This study was designed to investigate the antifungal activity of a hydroalcoholic extract from Flos Rosae Chinensis (FRC) combined with fluconazole (FCZ) against clinical isolates of Candida albicans resistant to FCZ. The minimum inhibitory concentration (MIC) of FRC was determined using a checkerboard microdilution assay. The synergistic effects of the combination of FRC and FCZ against clinical isolates of C. albicans resistant to FCZ were further confirmed by constructing time-growth curves and performing an agar diffusion test. FRC alone exerted efficient antifungal activities against C. albicans within a MIC₈₀ ranging from 20 μg/ml to 40 μg/ml. FRC failed to enhance the effects of FCZ against sensitive C. albicans strains, although it rendered FCZ-resistant C. albicans more sensitive. These results were further confirmed by the result of in vivo study. Our study is the first to discover that FRC can inhibit the growth of C. albicans to a certain degree. An FRC antifungal mechanism study showed that FRC strengthens FCZ to inhibit the action of ergosterol biosynthesis by promoting the transformation of lanosterol to eburicol, suggesting that the antifungal mechanism of FRC involves the inhibition of ergosterol biosynthesis.

Identification of small molecules that disrupt vacuolar function in the pathogen Candida albicans

The fungal vacuole is a large acidified organelle that performs a variety of cellular functions. At least a sub-set of these functions are crucial for pathogenic species of fungi, such as Candida albicans, to survive within and invade mammalian tissue as mutants with severe defects in vacuolar biogenesis are avirulent. We therefore sought to identify chemical probes that disrupt the normal function and/or integrity of the fungal vacuole to provide tools for the functional analysis of this organelle as well as potential experimental therapeutics. A convenient indicator of vacuolar integrity based upon the intracellular accumulation of an endogenously produced pigment was adapted to identify Vacuole Disrupting chemical Agents (VDAs). Several chemical libraries were screened and a set of 29 compounds demonstrated to reproducibly cause loss of pigmentation, including 9 azole antifungals, a statin and 3 NSAIDs. Quantitative analysis of vacuolar morphology revealed that (excluding the azoles) a sub-set of 14 VDAs significantly alter vacuolar number, size and/or shape. Many C. albicans mutants with impaired vacuolar function are deficient in the formation of hyphal elements, a process essential for its pathogenicity. Accordingly, all 14 VDAs negatively impact C. albicans hyphal morphogenesis. Fungal selectivity was observed for approximately half of the VDA compounds identified, since they did not alter the morphology of the equivalent mammalian organelle, the lysosome. Collectively, these compounds comprise of a new collection of chemical probes that directly or indirectly perturb normal vacuolar function in C. albicans.

Cinnamaldehyde and its derivatives, a novel class of antifungal agents

The last few decades have seen an alarming rise in fungal infections, which currently represent a global health threat. Despite extensive research towards the development of new antifungal agents, only a limited number of antifungal drugs are available in the market. The routinely used polyene agents and many azole antifungals are associated with some common side effects such as severe hepatotoxicity and nephrotoxicity. Also, antifungal resistance continues to grow and evolve and complicate patient management, despite the introduction of new antifungal agents. This suitation requires continuous attention. Cinnamaldehyde has been reported to inhibit bacteria, yeasts, and filamentous molds via the inhibition of ATPases, cell wall biosynthesis, and alteration of membrane structure and integrity. In this regard, several novel cinnamaldehyde derivatives were synthesized with the claim of potential antifungal activities. The present article describes antifungal properties of cinnamaldehyde and its derivatives against diverse classes of pathogenic fungi. This review will provide an overview of what is currently known about the primary mode of action of cinnamaldehyde. Synergistic approaches for boosting the effectiveness of cinnamaldehyde and its derivatives have been highlighted. Also, a keen analysis of the pharmacologically active systems derived from cinnamaldehyde has been discussed. Finally, efforts were made to outline the future perspectives of cinnamaldehyde-based antifungal agents. The purpose of this review is to provide an overview of current knowledge about the antifungal properties and antifungal mode of action of cinnamaldehyde and its derivatives and to identify research avenues that can facilitate implementation of cinnamaldehyde as a natural antifungal.

Invasive Primary Colonic Aspergillosis in the Immunocompetent Host without Classical Risk Factors

Invasive aspergillosis (IA), generally considered an opportunistic infection in immunocompromised hosts, is associated with high morbidity and mortality. IA commonly occurs in the respiratory tract with isolated reports of aspergillosis infection in the nasal sinuses, central nervous system, skin, liver, and urinary tract. Extra-pulmonary aspergillosis is usually observed in disseminated disease. To date, there are a few studies regarding primary and disseminated gastrointestinal (GI) aspergillosis in immunocompromised hosts. Only a few cases of primary GI aspergillosis in non-immunocompromised hosts have been reported; of these, almost all of them involved the upper GI tract. We describe a very rare case of IA involving the lower GI tract in the patient without classical risk factors that presented as multiple colon perforations and was successfully treated by surgery and antifungal treatment. We also review related literature and discuss the characteristics and risk factors of IA in the immunocompetent hosts without classical risk factors. This case that shows IA should be considered in critically ill patients, and that primary lower GI aspergillosis may also occur in the immunocompetent hosts without classical risk factors.

Invasive fungal infections in pediatric hematopoietic stem cell transplant patients

BACKGROUND

Pediatric hematopoietic stem cell transplant (HSCT) recipients are at high risk of invasive fungal infections (IFIs).

METHODS

To characterize IFIs and changes in fungal organisms over time in pediatric HSCT patients, we performed a retrospective cohort study of all HSCTs performed in pediatric patients at UCLA between 1991 and 2006.

RESULTS

In all, 318 patients underwent 324 HSCT transplants over the 15-year period and 69 unique fungal infections were identified in 47 transplant patients. The overall incidence of fungal infections in HSCT recipients was 14.5%, with predominant organisms including Candida species (51%) and Aspergillus species (26%), with Candida albicans accounting for 18.8% of all fungal species. The distribution of organisms over time demonstrated a strong trend towards an increase in rare molds in more recent years. The respiratory tract was the main site of infection (52.6%), with urine and blood also noted as significant sites. Of all deaths in the patients with IFIs, fungal-related mortality accounted for 67.6% of deaths.

CONCLUSIONS

HSCT patients have a much higher risk of fungal infections with rarer organisms becoming more prevalent, a finding likely linked to evolving antifungal practices over time. This emphasizes the need for the development and implementation of improved diagnostic, prophylactic, and therapeutic strategies to improve patient survival.

Distribution of yeast-like fungi at a university hospital in Turkey

Background:

The increased life span has led to application of more invasive procedures for diagnosis and treatment of particularly immunosuppressed individuals. This situation drew more attention to fungal infections due to existence of yeast-like fungi. Candida infections have increased due to transplant in patients, prolonged intensive care unit (ICU) stays, and invasive procedures. Recently, identification of yeast-like fungi as well as antifungal susceptibility test has been gaining more importance.

Objectives:

In our study, we aimed to evaluate the distribution of yeast-like fungi strains isolated from blood, urine, wound and respiratory specimens, which were sent from various departments of Izmir University School of Medicine University Hospital.

Materials and Methods:

The 262 yeast strains (of 13860 clinical specimens), isolated during 30.05.2012-20.05.2013, which were sent from various departments of Izmir University School of Medicine to Medical Microbiology Laboratory, were included in this study. Blood, wound, respiratory (sputum, tracheal secretion), and urine specimens were cultivated on blood agar and Sabouraud dextrose agar and incubated for 24-48 hours at 37°C. The isolates were cultivated on CHROMagar Candida and Cornmeal Tween 80 medium for identification. Besides, the automatized Vitek version 2.0 system was used for identification of the yeast strains as well as the antifungal susceptibility of blood culture strains.

Results:

A total of 262 strains, isolated from the Anesthesiology and Reanimation Unit, as well as from the departments of Hematology, Urology, Infectious Diseases, Gynecology and Obstetrics, and Ear Nose and Throat, were included in this study. The most common isolated yeast-like species was Candida albicans. C. parapsilosis was the most common yeast-like fungus isolated from blood cultures. All the blood culture strains were susceptible to amphotericin B, flucytosine, fluconazole and voriconazole.

Conclusions:

Candida strains isolated from newborns, elderly patients, and intensive care patients, identified and isolates from blood cultures, should be studied for antifungal susceptibility for management of the treatment. Our University Hospital is a recently opened center and these are the first data of our center. Gradually, as the number of patients increases, this data will be evaluated further.

Novel insights into host-fungal pathogen interactions derived from live-cell imaging

The theoretical physicist and Nobel laureate Richard Feynman outlined in his 1959 lecture, “There’s plenty of room at the bottom”, the enormous possibility of producing and visualising things at smaller scales. The advent of advanced scanning and transmission electron microscopy and high-resolution microscopy has begun to open the door to visualise host-pathogen interactions at smaller scales, and spinning disc confocal and two-photon microscopy has improved our ability to study these events in real time in three dimensions. The aim of this review is to illustrate some of the advances in understanding host-fungal interactions that have been made in recent years in particular those relating to the interactions of live fungal pathogens with phagocytes. Dynamic imaging of host-pathogen interactions has recently revealed novel detail and unsuspected mechanistic insights, facilitating the dissection of the phagocytic process into its component parts. Here, we will highlight advances in our knowledge of host-fungal pathogen interactions, including the specific effects of fungal cell viability, cell wall composition and morphogenesis on the phagocytic process and try to define the relative contributions of neutrophils and macrophages to the clearance of fungal pathogens in vitro and the infected host.

Invasive pulmonary aspergillosis

In susceptible patients, invasive aspergillosis has a high incidence and a mortality of up to 80%. The diagnosis of this condition is difficult, especially in the early stages of the disease and, as a consequence, antifungal therapy, despite its expense and toxicity, is often initiated empirically. Until recently, there were very few effective antifungal agents for established invasive aspergillosis, but the introduction of two new drugs, voriconazole and caspofungin, has increased the treatment options. These newer antifungal therapies, combined with improved early diagnosis due to the introduction of newer microbiologic techniques, offer the hope that there will be a significant improvement in the substantial morbidity and mortality associated with invasive aspergillosis over the next 5 years.

Fungal infections in cancer patients

Invasive fungal infections (IFI) have become a leading cause of morbidity and mortality in cancer patients. Infections with these organisms are often difficult to diagnose and treat. Appropriate and timely diagnosis requires a high index of suspicion and invasive procedures, including biopsy, to confirm the diagnosis. Treatment may be difficult, secondary to variable susceptibility and difficulty with exact and specific characterization of the fungal pathogen. The pathogens that are seen range from yeasts to invasive molds. Fortunately newer, noninvasive diagnostic techniques are available to aid in the diagnosis and treatments have become better tolerated and more efficacious.

Altered dynamics of Candida albicans phagocytosis by macrophages and PMNs when both phagocyte subsets are present

An important first line of defense against Candida albicans infections is the killing of fungal cells by professional phagocytes of the innate immune system, such as polymorphonuclear cells (PMNs) and macrophages. In this study, we employed live-cell video microscopy coupled with dynamic image analysis tools to provide insights into the complexity of C. albicans phagocytosis when macrophages and PMNs were incubated with C. albicans alone and when both phagocyte subsets were present. When C. albicans cells were incubated with only one phagocyte subtype, PMNs had a lower overall phagocytic capacity than macrophages, despite engulfing fungal cells at a higher rate once fungal cells were bound to the phagocyte surface. PMNs were more susceptible to C. albicans-mediated killing than macrophages, irrespective of the number of C. albicans cells ingested. In contrast, when both phagocyte subsets were studied in coculture, the two cell types phagocytosed and cleared C. albicans at equal rates and were equally susceptible to killing by the fungus. The increase in macrophage susceptibility to C. albicans-mediated killing was a consequence of macrophages taking up a higher proportion of hyphal cells under these conditions. In the presence of both PMNs and macrophages, C. albicans yeast cells were predominantly cleared by PMNs, which migrated at a greater speed toward fungal cells and engulfed bound cells more rapidly. These observations demonstrate that the phagocytosis of fungal pathogens depends on, and is modified by, the specific phagocyte subsets present at the site of infection.

Extensive work investigating fungal cell phagocytosis by macrophages and PMNs of the innate immune system has been carried out. These studies have been informative but have examined this phenomenon only when one phagocyte subset is present. The current study employed live-cell video microscopy to break down C. albicans phagocytosis into its component parts and examine the effect of a single phagocyte subset, versus a mixed phagocyte population, on these individual stages. Through this approach, we identified that the rate of fungal cell engulfment and rate of phagocyte killing altered significantly when both macrophages and PMNs were incubated in coculture with C. albicans compared to the rate of either phagocyte subset incubated alone with the fungus. This research highlights the significance of studying pathogen-host cell interactions with a combination of phagocytes in order to gain a greater understanding of the interactions that occur between cells of the host immune system in response to fungal invasion.

A case of disseminated blastomycosis in Vermont

Blastomyces dermatitides is increasingly found in Canada along the St. Lawrence River. However, there are only rare reports of this disease in New England. We describe a case of disseminated blastomycosis in a patient from northern Vermont who acquired the fungus while gardening.

Efficient bioconversion of echinocandin B to its nucleus by overexpression of deacylase genes in different host strains

Anidulafungin, which noncompetitively inhibits β-(1,3)-D-glucan synthase in fungal cell wall biosynthesis, is the newest antifungal drug to be developed. Echinocandin B deacylase from Actinoplanes utahensis NRRL 12052 catalyzes the cleavage of the linoleoyl group of echinocandin B, a key step in the process of manufacturing anidulafungin. Unfortunately, the natural yield of echinocandin B nucleus is low. In our study, the echinocandin B deacylase gene was systematically overexpressed by genetic engineering in its original producer, A. utahensis, and in the heterologous hosts Streptomyces lividans TK24 and Streptomyces albus. The introduction of additional copies of the gene, under the control of PermE* or its native promoter, into hosts showed significant increases in its transcription level and in the efficiency of the bioconversion of echinocandin B to its nucleus. The conditions for the cultivation and bioconversion of A. utahensis have been optimized further to improve production. As a result, while the wild-type strain initially produced 0.36 g/liter, a concentration of 4.21 g/liter was obtained after the generation of a strain with additional copies of the gene and further optimization of the reaction conditions. These results are useful for enhancing echinocandin B nucleus production in A. utahensis. Our study could enable the engineering of commercially useful echinocandin B nucleus-overproducing stains.

Th17 cells in immunity to Candida albicans

Our understanding of immunity to fungal pathogens has advanced considerably in recent years. Particularly significant have been the parallel discoveries in the C-type lectin receptor family and the Th effector arms of immunity, especially Th17 cells and their signature cytokine, IL-17. Many of these studies have focused on the most common human fungal pathogen, Candida albicans, which is typically a commensal microbe in healthy individuals but causes various disease manifestations in immunocompromised hosts, ranging from mild mucosal infections to lethal disseminated disease. Here, we discuss emerging fundamental discoveries with C. albicans that have informed our overall molecular understanding of fungal immunity. In particular, we focus on the importance of pattern recognition receptor-mediated fungal recognition and subsequent IL-17 responses in host defense against mucosal candidiasis. In light of these recent advances, we also discuss the implications for anticytokine biologic therapy and vaccine development.

A rescue therapy with a combination of caspofungin and liposomal amphotericin B or voriconazole in children with haematological malignancy and refractory invasive fungal infections

Combination treatment of paediatric invasive fungal infections (IFIs) has rarely been reported. A total of 17 children with 19 IFI episodes were enrolled in the study. The median age of the patients was 5.3 (range 0.5-17) years. IFI was classified as proven in 4, probable in 12 and possible in 3 episodes. These patients received empiric antifungal treatment, which consisted of liposomal amphotericin B (LAmB) monotherapy for a median duration of 12 days (range 3-69 days). All patients were refractory to LAmB; therefore, caspofungin was added to the therapy in 11 patients. In the remaining six patients, LAmB was ceased and a combination of caspofungin and voriconazole was started. Among the patients who received caspofungin + LAmB, four did not show favourable response and the combination was switched to caspofungin + voriconazole. The median (range) and total duration of the therapy were 7 (3-14) days and 91 patient days for LAmB + caspofungin combination and 49 (7-126) days and 516 patient days for caspofungin + voriconazole combination. We found a favourable response rate of 68.4% in 16 proven or probable IFI episodes. Twelve-week survival rate of these patients was 75%. No serious side effect was observed among the patients. Our data suggest that combination antifungal therapy is safe and effective in children with haematological malignancies.

A Protective Mechanism in Lungs of Rats Experimentally Infected with Aspergillus fumigatus

Aspergillus fumigatus is associated with invasive disease aspergillosis in immunocompromised individuals. The major aim of this study was to investigate the biochemical and immunological responses of male Wistar rats against A. fumigatus experimentally-induced pulmonary fungal infection. Nostril experimental exposure of male Wistar rats to a high dose of A. fumigatus freeze-dried preparation for only 24 hr resulted in a significant increase in levels of catalase, nitric oxide and lipid peroxide in lung homogenates, compared to those of the control animals. However, the oxidative status of the lungs of rats challenged with killed fungus did not change significantly, except for the stimulation in the level of lipid peroxide. IgG level was significantly elevated only in rats that received two low doses of fungus, compared to unexposed animals (p<0.005). Examining the lung of rats exposed to A. fumigatus revealed no abnormal changes, except for pus in bronchial lumen spaces and per bronchial inflammation. Histologically, large numbers of granuloma cells were evident in the lungs of challenged rats, while no granuloma formation was evident in the lungs of rats exposed to killed fungus.

Glycosylation status of the C. albicans cell wall affects the efficiency of neutrophil phagocytosis and killing but not cytokine signaling

The cell wall of the opportunistic human fungal pathogen, Candida albicans is a complex, layered network of rigid structural polysaccharides composed of β-glucans and chitin that is covered with a fibrillar matrix of highly glycosylated mannoproteins. Polymorphonuclear cells (PMNs, neutrophils) are the most prevalent circulating phagocytic leukocyte in peripheral blood and they are pivotal in the clearance of invading fungal cells from tissues. The importance of cell-wall mannans for the recognition and uptake of C. albicans by human PMNs was therefore investigated. N- and O-glycosylation-deficient mutants were attenuated in binding and phagocytosis by PMNs and this was associated with reduced killing of C. albicans yeast cells. No differences were found in the production of the respiratory burst enzyme myeloperoxidase (MPO) and the neutrophil chemokine IL-8 in PMNs exposed to control and glycosylation-deficient C. albicans strains. Thus, the significant decrease in killing of glycan-deficient C. albicans strains by PMNs is a consequence of a marked reduction in phagocytosis rather than changes in the release of inflammatory mediators by PMNs.

Identification of 3-phenylaminoquinolinium and 3-phenylaminopyridinium salts as new agents against opportunistic fungal pathogens

Previous studies on the indoloquinoline alkaloid, cryptolepine (2), revealed that it has antii-nfective properties among other activities. Using Structure-activity relationship (SAR) techniques, several ring-opened analogs of cryptolepine (3-phenylaminopyridinium and 3-phenylaminoquinolinium derivatives) were designed to improve the potency and lower the cytotoxicity shown by several of the precursor agents. Results indicate that these ring-opened analogs constitute new anti-infective agents with over a 100-fold potency and several fold lower cytotoxicity than cryptolepine from which they are derived.

Systematic internal transcribed spacer sequence analysis for identification of clinical mold isolates in diagnostic mycology: a 5-year study

The implementation of internal transcribed spacer (ITS) sequencing for routine identification of molds in the diagnostic mycology laboratory was analyzed in a 5-year study. All mold isolates (n = 6,900) recovered in our laboratory from 2005 to 2009 were included in this study. According to a defined work flow, which in addition to troublesome phenotypic identification takes clinical relevance into account, 233 isolates were subjected to ITS sequence analysis. Sequencing resulted in successful identification for 78.6% of the analyzed isolates (57.1% at species level, 21.5% at genus level). In comparison, extended in-depth phenotypic characterization of the isolates subjected to sequencing achieved taxonomic assignment for 47.6% of these, with a mere 13.3% at species level. Optimization of DNA extraction further improved the efficacy of molecular identification. This study is the first of its kind to testify to the systematic implementation of sequence-based identification procedures in the routine workup of mold isolates in the diagnostic mycology laboratory.

Exogenous interferon-gamma immunotherapy for invasive fungal infections in kidney transplant patients

The incidence of invasive fungal infections (IFIs) in nonneutropenic solid organ transplant patients is increasing. We report our clinical experience with the use of interferon-gamma (IFN-gamma) immunotherapy in seven renal transplant patients who developed life threatening, disseminated IFIs refractory to conventional antifungal drug therapy. The infections were all microbiologically and histologically proven. The rapid cure of these disseminated infections with exogenous IFN-gamma injections was not associated with impaired kidney allograft function despite the use of liposomal amphotericin B in all cases. No clinical toxicity from the IFN-gamma immunotherapy was seen and no IFI relapsed during long-term follow-up. Our experience is both uncontrolled and in patients with unpredictable fungal infection-related outcomes. However, compared to standard approaches, the accelerated cure of life threatening, disseminated IFIs with 6 weeks of combination antifungal drug therapy and IFN-gamma immunotherapy saved lives, retained allograft function and led to substantial cost savings in this small patient group.

A novel polyamide SL-A92 as a potential fungal resistance blocker: synthesis and bioactivities in Candida albicans

AIM

To synthesize a novel polyamide SL-A92 and evaluate its bioactivity against drug resistance in Candida albicans.

METHODS

SL-A92 was synthesized using N-hydroxybenzotriazole (HOBT)/N,N'-dicyclohexylcarbodiimide (DCC) in solution phase. Its antifungal activities and effects on strain growth were tested using the micro-broth dilution method and growth curves, respectively. Induced drug resistance in the C. albicans collection strain SC5314 was obtained by incubation with fluconazole (12 microg/mL) for 21 passages. Meanwhile, incubations with SL-A92 plus fluconazole were also carried out in SC5314 strains, and the MIC(80)s were used to evaluate the inhibitory effects of SL-A92 on drug resistance during the induction process. Real time RT-PCR was performed to investigate the CDR1 and CDR2 mRNA levels in induced SC5314 strains.

RESULTS

SC5314 strain induced by the combination of fluconazole and SL-A92 (200 microg/mL) did not develop drug resistance. On day 24, the CDR1 and CDR2 mRNA levels in SC5314 strain co-treated with fluconazole and SL-A92 relative to fluconazole alone were 26% and 24%, respectively, and on day 30 the CDR1 and CDR2 mRNA levels were 43% and 31%, respectively.

CONCLUSION

SL-A92 can block the development of drug resistance during the fluconazole induction process, which partially results from the down-regulation of CDR1 and CDR2.

Interaction of Candida albicans biofilms with antifungals: transcriptional response and binding of antifungals to beta-glucans

Candida albicans can form biofilms that exhibit elevated intrinsic resistance to various antifungal agents, in particular azoles and polyenes. The molecular mechanisms involved in the antifungal resistance of biofilms remain poorly understood. We have used transcript profiling to explore the early transcriptional responses of mature C. albicans biofilms exposed to various antifungal agents. Mature C. albicans biofilms grown under continuous flow were exposed for as long as 2 h to concentrations of fluconazole (FLU), amphotericin B (AMB), and caspofungin (CAS) that, while lethal for planktonic cells, were not lethal for biofilms. Interestingly, FLU-exposed biofilms showed no significant changes in gene expression over the course of the experiment. In AMB-exposed biofilms, 2.7% of the genes showed altered expression, while in CAS-exposed biofilms, 13.0% of the genes had their expression modified. In particular, exposure to CAS resulted in the upregulation of hypha-specific genes known to play a role in biofilm formation, such as ALS3 and HWP1. There was little overlap between AMB- or CAS-responsive genes in biofilms and those that have been identified as AMB, FLU, or CAS responsive in C. albicans planktonic cultures. These results suggested that the resistance of C. albicans biofilms to azoles or polyenes was due not to the activation of specific mechanisms in response to exposure to these antifungals but rather to the intrinsic properties of the mature biofilms. In this regard, our study led us to observe that AMB physically bound C. albicans biofilms and beta-glucans, which have been proposed to be major constituents of the biofilm extracellular matrix and to prevent azoles from reaching biofilm cells. Thus, enhanced extracellular matrix or beta-glucan synthesis during biofilm growth might prevent antifungals, such as azoles and polyenes, from reaching biofilm cells, thus limiting their toxicity to these cells and the associated transcriptional responses.

Influence of fluoroquinolones on phagocytosis and killing of Candida albicans by human polymorphonuclear neutrophils

Candida albicans infections often occur during or shortly after antibacterial treatment. Phagocytosis by polymorphonuclear neutrophil granulocytes (PMN) is the most important primarily defence mechanism against C. albicans. Certain antibiotics such as some fluoroquinolones (FQ) are known to influence phagocyte functions. Thus, we investigated the influence of older and newer FQ on the phagocytosis and killing of C. albicans by human PMN paying special attention to CD11b expression of these cells as an indicator of the degree of their activation. In order to obtain comprehensive and comparable results we tested 13 FQ over a wide range of concentrations and in a time dependent manner in a standardized approach. When used at therapeutic concentrations, the FQ tested did not influence to a clinically significant degree the phagocytosis or the killing of C. albicans by human PMN and also not their activation. However, at high concentrations those FQ with cyclopropyl-moiety at position N1 showed increase in CD11b expression and diminished phagocytosis and oxidative burst.