Vascular pythiosis caused by Pythium aphanidermatum: the first case report in Asia

BACKGROUND

Pythium, soil-borne plant pathogens, are in the class Oomycetes. They are not true fungi, but are related to diatom and algae. There are two human pathogens including P. insidiosum and P. aphanidermatum. To date, only one case of pythiosis caused by P. aphanidermatum has been reported. We present herein the first case of P. aphanidermatum vascular pythiosis in Asia.

CASE PRESENTATION

A 47-year-old Thai woman, living in North Thailand, with ß thalassemia/hemoglobin E presented with acute recurrent arterial insufficiency of both legs. Emergent embolectomy with clot removal was performed. The pathology of the clot exhibited noncaseous granulomatous inflammation with many fungal hyphal elements. PCR identified P. aphanidermatum with 100% identity. Final diagnosis is vascular pythiosis. Unfortunately, the patient eventually expired after treatment with itraconazole, terbinafine, azithromycin, and doxycycline.

CONCLUSIONS

To date, only one case of pythiosis caused by P. aphanidermatum has been reported. We present herein the first case of P. aphanidermatum vascular pythiosis in Asia.

Role of antimicrobial peptides in atopic dermatitis

Host defense peptides (HDPs) or antimicrobial peptides (AMPs) are short cationic amphipathic peptides of divergent sequences, which are part of the innate immune system and produced by various types of cells and tissues. The predominant role of HDPs is to respond to and protect humans against infection and inflammation. Common human HDPs include defensins, cathelicidin, psoriasin, dermcidin, and ribonucleases, but these peptides may be dysregulated in the skin of patients with atopic dermatitis (AD). Current evidence suggests that the antimicrobial properties and immunomodulatory effects of HDPs are involved in AD pathogenesis, making HDPs research a promising area for predicting disease severity and developing novel treatments for AD. In this review, we describe a potential role for human HDPs in the development, exacerbation, and progression of AD and propose their potential therapeutic benefits.

Methylene blue-mediated photodynamic therapy may be superior to 5% amorolfine nail lacquer for non-dermatophyte onychomycosis

BACKGROUND

Methylene blue-mediated photodynamic therapy as an antimicrobial has been reported to improve onychomycosis.

OBJECTIVES

To compare the short-term efficacy of methylene blue-mediated photodynamic therapy (MB-PDT) and 5% amorolfine nail lacquer (AMO) for toenail onychomycosis using higher intensity and shorter total treatment period than previously reported.

METHODS

Twenty-seven toenails with onychomycosis were randomized to receive either six biweekly sessions of MB-PDT or AMO for twelve weeks. Dermoscopic photography was used for onychomycosis severity index assessment under a dermoscopic inspection (d-OSI) at baseline, weeks 6, 10, 14 and 22 as well as microscopic and microbiological tests. Adverse events were recorded.

RESULTS

All subjects completed the study. Causative organisms found were exclusively non-dermatophytes including Fusarium spp., Asperillus spp.,and yeasts. Fifteen toenails received MB-PDT, whilst 12 received AMO. D-OSI showed greater improvement in MB-PDT than in AMO groups at weeks 6, 10, 14 as well as 22, with median changes of -2, -3, -4 (P = .055). and - 3 respectively in the MB-PDT group. The AMO group displayed the median d-OSI change of 0 throughout the study period. Mycological cure rate at 22 weeks in MB-PDT and AMO group was 73.3% and 66.67% (P > .05). Clinical cure rate at 22 weeks in MB-PDT (26.7%) was higher than AMO (16.7%), (P > .05). All patients only felt comfortably warm during the MB-PDT treatment. No major adverse events were found in both groups.

CONCLUSIONS

MB-PDT appeared to be more efficacious for non-dermatophyte onychomycosis than AMO particularly in a limited period and moderately severe onychomycosis.

The Inhibitory Effect of Human Beta-defensin-3 on Candida Glabrata Isolated from Patients with Candidiasis

Candida glabrata is a common non-albicans Candida species found in patients with candidiasis and it sometimes develops antifungal resistance. Human beta-defensin-3 (hBD-3) is an antimicrobial peptide of immune system active against various types of microbes including Candida spp. This study investigated antifungal activity of hBD-3 and its synergistic effect with a first-line antifungal agent on C. glabrata clinical isolates. Candida spp. were characterised in patients with candidiasis. The antifungal activities of hBD-3 and fluconazole against C. glabrata were evaluated using Broth microdilution assay. The synergistic activity of these two agents was determined by checkerboard microdilution and time-killing assays. The cytotoxicity of hBD-3 was evaluated using LDH-cytotoxicity colorimetric assay. Of 307 episodes from 254 patients diagnosed with candidiasis, C. glabrata was found in 21 clinical isolates. Antifungal susceptibility tests of C. glabrata were performed, fluconazole demonstrated an inhibitory effect at concentrations of 0.25-8 μg/ml, but one antifungal resistant strain was identified (>64 μg/ml). hBD-3 showed an inhibitory effect against all selected strains at concentrations of 50-75 μg/ml and exhibited a synergistic effect with fluconazole at the fractional inhibitory concentration index (FICI) of 0.25-0.50. A concentration of 25 μg/ml of hBD-3 alone showed no cytotoxicity but synergistic activity was seen with fluconazole. In conclusion, hBD-3 has antifungal activity against C. glabrata and synergistic effects with fluconazole at concentrations that alone, have no cytotoxicity. hBD-3 could be used as an adjunctive therapy with first-line antifungal agents for patients with C. glabrata infection particularly those infected with fluconazole-resistant strains.

Synthesis and Antimicrobial Activity of Novel 4-Hydroxy-2-quinolone Analogs

Alkyl quinolone has been proven to be a privileged scaffold in the antimicrobial drug discovery pipeline. In this study, a series of new 4-hydroxy-2-quinolinone analogs containing a long alkyl side chain at C-3 and a broad range of substituents on the C-6 and C-7 positions were synthesized. The antibacterial and antifungal activities of these analogs against Staphylococcus aureus, Escherichia coli, and Aspergillus flavus were investigated. The structure-activity relationship study revealed that the length of the alkyl chain, as well as the type of substituent, has a dramatic impact on the antimicrobial activities. Particularly, the brominated analogs 3j with a nonyl side chain exhibited exceptional antifungal activities against A. flavus (half maximal inhibitory concentration (IC₅₀) = 1.05 µg/mL), which surpassed that of the amphotericin B used as a positive control. The antibacterial activity against S. aureus, although not as potent, showed a similar trend to the antifungal activity. The data suggest that the 4-hydroxy-2-quinolone is a promising framework for the further development of new antimicrobial agents, especially for antifungal treatment.

The clinical significance of fungi in atopic dermatitis

Atopic dermatitis (AD) is one of the most common chronic inflammatory skin diseases and is caused by multiple factors including genetic factors, skin barrier defects, host immune responses, allergen sensitivity, environmental effects, and infections. Commonly, bacterial and viral infections are present in the eczematous lesions of AD patients and clearly aggravate the symptoms. However, studies of fungal infections in AD are limited in spite of the fact that there are reports showing that Malassezia, Candida, and some dermatophytes can affect the symptoms of AD. Moreover, certain fungal infections are sometimes overlooked and need to be considered particularly in AD patients with treatment failure as clinical features of those fungal infections could mimic eczematous lesions in AD. Here, we review the epidemiology, pathogenesis, clinical manifestations, and overlooked features of fungal infections associated with the symptoms of AD including the diagnosis and effectiveness of fungal treatments in AD patients.

Hospital epidemiology and antimicrobial susceptibility of isolated methicillin-resistant Staphylococcus aureus: a one-year retrospective study at a tertiary care center in Thailand

BACKGROUND

Increased rates of Staphylococcus aureus resistance and its morbidity and mortality have raised concern about the strategy of antibiotic use.

OBJECTIVES

This study aimed to determine the prevalence of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant S. aureus (VRSA) isolates among Thai patients with S. aureus infection and to identify risk factors and appropriate antibiotics for these resistant strains.

METHODS

Data of culture-proven S. aureus isolates from clinical specimens during 2017 in King Chulalongkorn Memorial Hospital, Thailand, were retrospectively collected and classified as methicillin-sensitive S. aureus or MRSA by cefoxitin screening and oxacillin minimum inhibitory concentration by the Vitek 2 system. Each isolate was also tested for susceptibility to teicoplanin, erythromycin, clindamycin, linezolid, trimethoprim/sulfamethoxazole, ciprofloxacin, moxifloxacin, tetracycline, doxycycline, and vancomycin by Vitek 2. Demographic information and comorbidities from medical records were reviewed to identify risk factors for S. aureus infection.

RESULTS

MRSA isolates were identified in 147 (17%) of 890 patients with no different ratio in adults or children. A higher proportion of MRSA in hospital-acquired settings was observed (27% vs. 12%; p < 0.001). Comorbidities significantly associated with MRSA were chronic lung, cardiovascular, and neurological diseases. Atrial fibrillation, dementia, and benign prostatic hyperplasia were independently associated with MRSA isolation. Vancomycin was still susceptible to all kinds of infection. One VRSA isolate was from colonization.

CONCLUSION

The prevalence of MRSA in our facility seemed to be comparatively low. Vancomycin is still an appropriate option for MRSA coverage since all S. aureus isolates in our center were sensitive to vancomycin. However, careful attention is warranted since one colonization isolate was VRSA.

Alteration of macrophage immune phenotype in a murine sepsis model is associated with susceptibility to secondary fungal infection

BACKGROUND

Secondary fungal infection is a major complication in patients with sepsis-associated immunosuppression. However, sepsis-induced immune alterations related to fungal susceptibility have not been well characterized.

OBJECTIVES

To determine kinetic changes in the immune phenotype by determining the proportion of T cells, B cells and macrophages, and especially the expression of an immune exhaustion marker PD-1, in murine sepsis. In addition, sepsis -induced alterations of these immune cells were assessed in relation to susceptibility to secondary fungal infection.

METHODS

Cecal ligation and puncture (CLP) was used as a mouse sepsis model, with Candida albicans as the secondary systemic fungal infection. Splenic T cells, B cells and macrophages were assessed by flow cytometry.

RESULTS

Alterations in T cell and B cell numbers and the proportion of PD-1 expressing T cells and B cells in CLP mice were not clearly related to susceptibility to secondary Candida infection. By contrast, changes in levels of CD86+-activated macrophages, and the proportion of the PD-1+ population among the CD86+ macrophages in CLP mice were found to be related to secondary fungal infection susceptibility.

CONCLUSIONS

Macrophage activation and exhaustion might be a significant determinant in susceptibility to fungal infection, and outcomes of infection. This study provided more comprehensive knowledge pertinent to patient evaluation and therapeutics design in restoring host defenses against secondary fungal infection in those with sepsis.

An Ssd1 Homolog Impacts Trehalose and Chitin Biosynthesis and Contributes to Virulence in Aspergillus fumigatus

Regulation of fungal cell wall biosynthesis is critical to maintain cell wall integrity in dynamic fungal infection microenvironments. Genes involved in this response that impact fungal fitness and host immune responses remain to be fully defined. In this study, we observed that a yeast ssd1 homolog, ssdA, in the filamentous fungus Aspergillus fumigatus is involved in trehalose and cell wall homeostasis. An ssdA null mutant strain exhibited an increase in trehalose levels and a reduction in fungal colony growth rate. In contrast, overexpression of ssdA perturbed trehalose biosynthesis and reduced germination of conidia. The ssdA null mutant strain was more resistant to cell wall-perturbing agents, while overexpression of ssdA increased sensitivity. Overexpression of ssdA significantly increased chitin levels, and both loss and overexpression of ssdA altered subcellular localization of the class V chitin synthase CsmA. Strikingly, overexpression of ssdA abolished adherence to abiotic surfaces and severely attenuated the virulence of A. fumigatus in a murine model of invasive pulmonary aspergillosis. Despite the severe in vitro fitness defects observed upon loss of ssdA, neither surface adherence nor murine survival was impacted. In conclusion, A. fumigatus SsdA plays a critical role in cell wall homeostasis impacting A. fumigatus-host interactions.IMPORTANCE The incidence of life-threatening infections caused by the filamentous fungus Aspergillus fumigatus is increasing along with an increase in the number of fungal strains resistant to contemporary antifungal therapies. The fungal cell wall and the associated carbohydrates required for its synthesis and maintenance are attractive drug targets given that many genes encoding proteins involved in cell wall biosynthesis and integrity are absent in humans. Importantly, genes and associated cell wall biosynthesis and homeostasis regulatory pathways remain to be fully defined in A. fumigatus In this report, we identify SsdA as an important component of trehalose and fungal cell wall biosynthesis in A. fumigatus that consequently impacts the host immune response and fungal virulence in animal models of infection.

Volatile Chemical Composition, Antibacterial and Antifungal Activities of Extracts from Different Parts of Globba schomburgkii Hook.f

Globba schomburgkii Hook.f. is an ornamental plant that has recently found increasing demand as cut flowers, hence generating a significant number of by-products from different parts of the plant. To investigate the further applications of these by-products, twelve crude extracts from rhizomes, stalks, leaves, and flowers were prepared by serial exhaustive extraction. The volatile composition of these extracts was analyzed by GC/MS; a total of 89 compounds were identified, most of which were sesquiterpenes as well as some labdane-type diterpenes. The antimicrobial activities of these extracts were evaluated, revealing a correlation between the terpenoid content and antibacterial activities. Notably, the dichloromethane extracts of rhizomes and flowers, which contained the highest amount of terpenoids (e. g., α-gurjunene, guaia-9,11-diene, γ-bicyclohomofarnesal, β-caryophyllene, and caryophyllene oxide), displayed the most prominent antibacterial activities. This work demonstrates the potential use of the crude extracts from G. schomburgkii as natural antibacterial ingredients for pharmaceutical and other applications.

Protein Kinase A and High-Osmolarity Glycerol Response Pathways Cooperatively Control Cell Wall Carbohydrate Mobilization in Aspergillus fumigatus

Aspergillus fumigatus mitogen-activated protein kinases (MAPKs) are involved in maintaining the normal morphology of the cell wall and providing resistance against cell wall-damaging agents. Upon cell wall stress, cell wall-related sugars need to be synthesized from carbohydrate storage compounds. Here we show that this process is dependent on cAMP-dependent protein kinase A (PKA) activity and regulated by the high-osmolarity glycerol response (HOG) MAPKs SakA and MpkC. These protein kinases are necessary for normal accumulation/degradation of trehalose and glycogen, and the lack of these genes reduces glucose uptake and glycogen synthesis. Alterations in glycogen synthesis were observed for the sakA and mpkC deletion mutants, which also displayed alterations in carbohydrate exposure on the cell wall. Carbohydrate mobilization is controlled by SakA interaction with PkaC1 and PkaR, suggesting a putative mechanism where the PkaR regulatory subunit leaves the complex and releases the SakA-PkaC1 complex for activation of enzymes involved in carbohydrate mobilization. This work reveals the communication between the HOG and PKA pathways for carbohydrate mobilization for cell wall construction.IMPORTANCEAspergillus fumigatus is an opportunistic human pathogen causing allergic reactions or systemic infections such as invasive pulmonary aspergillosis, especially in immunocompromised patients. The fungal cell wall is the main component responsible for recognition by the immune system, due to the specific composition of polysaccharide carbohydrates exposed on the surface of the fungal cell wall called pathogen-associated molecular patterns (PAMPs). Key enzymes in the fungal cell wall biosynthesis are a good target for fungal drug development. This report elucidates the cooperation between the HOG and PKA pathways in the mobilization of carbohydrates for fungal cell wall biosynthesis. We suggest that the reduced mobilization of simple sugars causes defects in the structure of the fungal cell wall. In summary, we propose that SakA is important for PKA activity, therefore regulating the availability and mobilization of monosaccharides for fungal cell wall biosynthesis during cell wall damage and the osmotic stress response.

Interleukin 1α Is Critical for Resistance against Highly Virulent Aspergillus fumigatus Isolates

Heterogeneity among Aspergillus fumigatus isolates results in unique virulence potential and inflammatory responses. How these isolates drive specific immune responses and how this affects fungally induced lung damage and disease outcome are unresolved. We demonstrate that the highly virulent CEA10 strain is able to rapidly germinate within the immunocompetent lung environment, inducing greater lung damage, vascular leakage, and interleukin 1α (IL-1α) release than the low-virulence Af293 strain, which germinates with a lower frequency in this environment. Importantly, the clearance of CEA10 was consequently dependent on IL-1α, in contrast to Af293. The release of IL-1α occurred by a caspase 1/11- and P2XR7-independent mechanism but was dependent on calpain activity. Our finding that early fungal conidium germination drives greater lung damage and IL-1α-dependent inflammation is supported by three independent experimental lines. First, pregermination of Af293 prior to in vivo challenge drives greater lung damage and an IL-1α-dependent neutrophil response. Second, the more virulent EVOL20 strain, derived from Af293, is able to germinate in the airways, leading to enhanced lung damage and IL-1α-dependent inflammation and fungal clearance. Third, primary environmental A. fumigatus isolates that rapidly germinate under airway conditions follow the same trend toward IL-1α dependency. Our data support the hypothesis that A. fumigatus phenotypic variation significantly contributes to disease outcomes.

Filamentous fungal carbon catabolite repression supports metabolic plasticity and stress responses essential for disease progression

Aspergillus fumigatus is responsible for a disproportionate number of invasive mycosis cases relative to other common filamentous fungi. While many fungal factors critical for infection establishment are known, genes essential for disease persistence and progression are ill defined. We propose that fungal factors that promote navigation of the rapidly changing nutrient and structural landscape characteristic of disease progression represent untapped clinically relevant therapeutic targets. To this end, we find that A. fumigatus requires a carbon catabolite repression (CCR) mediated genetic network to support in vivo fungal fitness and disease progression. While CCR as mediated by the transcriptional repressor CreA is not required for pulmonary infection establishment, loss of CCR inhibits fungal metabolic plasticity and the ability to thrive in the dynamic infection microenvironment. Our results suggest a model whereby CCR in an environmental filamentous fungus is dispensable for initiation of pulmonary infection but essential for infection maintenance and disease progression. Conceptually, we argue these data provide a foundation for additional studies on fungal factors required to support fungal fitness and disease progression and term such genes and factors, DPFs (disease progression factors).

The Fungal Exopolysaccharide Galactosaminogalactan Mediates Virulence by Enhancing Resistance to Neutrophil Extracellular Traps

Of the over 250 Aspergillus species, Aspergillus fumigatus accounts for up to 80% of invasive human infections. A. fumigatus produces galactosaminogalactan (GAG), an exopolysaccharide composed of galactose and N-acetyl-galactosamine (GalNAc) that mediates adherence and is required for full virulence. Less pathogenic Aspergillus species were found to produce GAG with a lower GalNAc content than A. fumigatus and expressed minimal amounts of cell wall-bound GAG. Increasing the GalNAc content of GAG of the minimally pathogenic A. nidulans, either through overexpression of the A. nidulans epimerase UgeB or by heterologous expression of the A. fumigatus epimerase Uge3 increased the amount of cell wall bound GAG, augmented adherence in vitro and enhanced virulence in corticosteroid-treated mice to levels similar to A. fumigatus. The enhanced virulence of the overexpression strain of A. nidulans was associated with increased resistance to NADPH oxidase-dependent neutrophil extracellular traps (NETs) in vitro, and was not observed in neutropenic mice or mice deficient in NADPH-oxidase that are unable to form NETs. Collectively, these data suggest that cell wall-bound GAG enhances virulence through mediating resistance to NETs.

The ubiquitous mold A. fumigatus is isolated in over 80% of all patients with invasive aspergillosis (IA). A. nidulans is a relatively non-pathogenic species that rarely causes IA except in patients with chronic granulomatous disease (CGD), a hereditary disease characterized by impaired neutrophil function due to mutations in the NADPH oxidase complex. Here, we demonstrate that one factor underlying the differences in the intrinsic virulence between A. fumigatus and A. nidulans is the amount of the exopolysaccharide galactosaminogalactan that is associated with the cell wall of these species. A. fumigatus produces higher amounts of cell wall-associated galactosaminogalactan and is more resistant than A. nidulans to neutrophil killing by NADPH-oxidase dependent extracellular traps (NETs). Increasing cell wall-associated galactosaminogalactan in A. nidulans enhanced resistance to NETs and increased the virulence of this species to the same level as A. fumigatus in mice with intact NET formation. Collectively, these data suggest that A. nidulans is more sensitive than A. fumigatus to NADPH-oxidase dependent NETosis due to lower levels of cell wall-associated GAG.

IL-1α signaling is critical for leukocyte recruitment after pulmonary Aspergillus fumigatus challenge

Aspergillus fumigatus is a mold that causes severe pulmonary infections. Our knowledge of how A. fumigatus growth is controlled in the respiratory tract is developing, but still limited. Alveolar macrophages, lung resident macrophages, and airway epithelial cells constitute the first lines of defense against inhaled A. fumigatus conidia. Subsequently, neutrophils and inflammatory CCR2+ monocytes are recruited to the respiratory tract to prevent fungal growth. However, the mechanism of neutrophil and macrophage recruitment to the respiratory tract after A. fumigatus exposure remains an area of ongoing investigation. Here we show that A. fumigatus pulmonary challenge induces expression of the inflammasome-dependent cytokines IL-1β and IL-18 within the first 12 hours, while IL-1α expression continually increases over at least the first 48 hours. Strikingly, Il1r1-deficient mice are highly susceptible to pulmonary A. fumigatus challenge exemplified by robust fungal proliferation in the lung parenchyma. Enhanced susceptibility of Il1r1-deficient mice correlated with defects in leukocyte recruitment and anti-fungal activity. Importantly, IL-1α rather than IL-1β was crucial for optimal leukocyte recruitment. IL-1α signaling enhanced the production of CXCL1. Moreover, CCR2+ monocytes are required for optimal early IL-1α and CXCL1 expression in the lungs, as selective depletion of these cells resulted in their diminished expression, which in turn regulated the early accumulation of neutrophils in the lung after A. fumigatus challenge. Enhancement of pulmonary neutrophil recruitment and anti-fungal activity by CXCL1 treatment could limit fungal growth in the absence of IL-1α signaling. In contrast to the role of IL-1α in neutrophil recruitment, the inflammasome and IL-1β were only essential for optimal activation of anti-fungal activity of macrophages. As such, Pycard-deficient mice are mildly susceptible to A. fumigatus infection. Taken together, our data reveal central, non-redundant roles for IL-1α and IL-1β in controlling A. fumigatus infection in the murine lung.

Aspergillus spp. are ubiquitous in the environment, and even though individuals are regularly exposed to fungal spores clinical invasive disease is a rare manifestation. In contrast, individuals with weakened immune systems develop severe disease, such as invasive pulmonary aspergillosis (IPA). IPA is associated with extremely poor prognoses and unacceptably high mortality rates. Knowledge gained from understanding how immunocompetent mammals control Aspergillus challenge will help develop new immunomodulatory strategies aimed at improving patient outcomes. It is well known that neutrophils and monocytes are crucial immune cells that act to limit fungal growth. Our work demonstrates a central role for the cytokine IL-1α in orchestrating the optimal recruitment of neutrophils and monocytes, whereas IL-1β and the inflammasome are more important in activation of anti-fungal activity of the monocytes. Moreover, our studies indicate that CCR2⁺ monocytes are required for optimal production of IL-1α in the lungs of A. fumigatus challenged mice. Thus, our data highlight a crucial role of the IL-1 cytokine in mediating anti-fungal immunity which might be harnessed to treat clinical cases of IPA.

Endoplasmic reticulum localized PerA is required for cell wall integrity, azole drug resistance, and virulence in Aspergillus fumigatus

GPI-anchoring is a universal and critical post-translational protein modification in eukaryotes. In fungi, many cell wall proteins are GPI-anchored, and disruption of GPI-anchored proteins impairs cell wall integrity. After being synthesized and attached to target proteins, GPI anchors undergo modification on lipid moieties. In spite of its importance for GPI-anchored protein functions, our current knowledge of GPI lipid remodelling in pathogenic fungi is limited. In this study, we characterized the role of a putative GPI lipid remodelling protein, designated PerA, in the human pathogenic fungus Aspergillus fumigatus. PerA localizes to the endoplasmic reticulum and loss of PerA leads to striking defects in cell wall integrity. A perA null mutant has decreased conidia production, increased susceptibility to triazole antifungal drugs, and is avirulent in a murine model of invasive pulmonary aspergillosis. Interestingly, loss of PerA increases exposure of β-glucan and chitin content on the hyphal cell surface, but diminished TNF production by bone marrow-derived macrophages relative to wild type. Given the structural specificity of fungal GPI-anchors, which is different from humans, understanding GPI lipid remodelling and PerA function in A. fumigatus is a promising research direction to uncover a new fungal specific antifungal drug target.