Trends of ocular fungal infections in North China (2001-2020)

The Dual Pathogen Fusarium: Diseases, Incidence, Azole Resistance, and Biofilms

The increasing resistance of Fusarium species to nearly all first-line antifungal agents in clinical settings has led to its designation as a 'high-priority' human pathogen. As a dual pathogen, Fusarium spp. threaten both human health and crop production, impacting food security. Our recent drug profiling of clinical Fusarium isolates reveals resistance to several front-line antifungals, with notable cross-azole resistance observed in both clinical and plant-associated strains. While the overuse of agricultural azoles has been implicated in the selection of azole-resistant fungi such as Aspergillus, a similar mechanism has been assumed for Fusarium in clinical settings. However, direct genetic evidence supporting this hypothesis remains limited. In this review, part of our Special Interest (SI) series, we discuss the spectrum of human diseases caused by Fusarium. While incidence data are better established for human keratitis and onychomycosis, invasive fusariosis remains globally underreported. We propose reasons for this distinct clinical spectrum bias and explore the potential genetic basis of azole resistance.

Piperine inhibits fungal growth and protects against pyroptosis in Aspergillus fumigatus keratitis by regulating the mTOR/HIF-1α pathway

PURPOSE

To confirm the antifungal ability of piperine (PIP) and to assess its therapeutic potential in the treatment of Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

The toxicity of PIP was measured to determine the optimal therapeutic concentration both in human corneal epithelial cells (HCECs), RAW264.7 cells and mice fungal keratitis models. The antifungal efficacy of PIP was confirmed through the minimum inhibitory concentration (MIC) test, biofilm formation inhibition test, Calcofluor white and PI staining, and anti-adhesion of A. fumigatus conidia test. Hematoxylin-eosin (HE) staining, corneal fungal load assay, RT-qPCR, western blot, and Elisa were used to assess the therapeutic effect and anti-inflammatory ability of PIP in fungal keratitis. The significance of the mTOR/HIF-1α signal pathway after PIP treatment of A. fumigatus keratitis was evaluated.

RESULTS

PIP had no obvious toxicity to HCECs, RAW 264.7 cells, or mouse cornea at the concentration of 30 µg/mL. PIP effectively inhibited A. fumigatus from growing and showed synergistic effects when combined with NATA. PIP not only reduced fungal load and the aggregation of inflammatory cells, but also dramatically reduced the expression levels of NLRP3, caspase-1, cleaved caspase-1, GSDMD, GSDMD-N, IL-18, and IL-1β, which were linked to pyroptosis. Additionally, PIP decreased mTOR phosphorylation and HIF-1α expression. The pretreatment with mTOR agonists reversed the inhibition of NLRP3, caspase-1, cleaved caspase-1, GSDMD, GSDMD-N, IL-18, and IL-1β protein levels caused by PIP.

CONCLUSION

PIP exhibited antifungal and anti-inflammatory properties, and alleviated pyroptosis in A. fumigatus keratitis via inhibiting the mTOR/HIF-1α signaling pathway.

Assessing the Efficacy of Chlorhexidine in Combating Most Important Causative Agents of Fungal Keratitis: An in Vitro Comparative Study With Seven Antifungal Agents

PURPOSE

Fungal keratitis (FK) is a difficult condition to treat, particularly in underdeveloped nations. The study aimed to compare the in vitro activity of chlorhexidine (CHX) and seven antifungal agents against a collection of fungi recovered from FK patients.

METHODS

Seventy-three fungi were collected from patients with FK included in study. The antifungal agents tested were fluconazole, voriconazole, posaconazole, miconazole, natamycin, amphotericin B, and caspofungin. The concentration range for CHX was 1-1024 μg/mL. Assessments of antifungal susceptibility were conducted using the EUCAST broth microdilution reference method.

RESULTS

The findings demonstrated the beneficial in vitro inhibition of filamentous and yeast fungi by CHX. CHX demonstrated efficacy against Fusarium spp., Aspergillus spp., Candida spp., S. apiospermum and dematiceous fungi at concentrations of 4-64, 32-64, 4-32, 8, and 4-16 µg/mL respectively. The median MICs and MIC distributions of CHX showed no significant differences among the evaluated spp. (p > 0.05). The most effective antifungal drug was posaconazole, which was followed by voriconazole, caspofungin, and amphotericin B.

CONCLUSION

In situations where access to a range of antifungal medications and microbiological facilities is limited, CHX should be further investigated as a potential treatment for FK. It might be able to treat the condition as an inexpensive topical treatment.

Comparative analysis of the therapeutic efficacy of low-temperature plasma ablation in treating fungal keratitis caused by various strains

OBJECTIVE

The objective of this study is to assess the therapeutic efficacy of low-temperature plasma ablation (LTP) combined with drug treatment in the treatment of fungal keratitis (FK) caused by various pathogens, thereby establishing a clinical foundation for the use of LTP in treating FK.

METHODS

A retrospective study was performed, including 76 patients (76 eyes) with FK diagnosed at the Affiliated Eye Hospital of Nanchang University. The patients were categorized into the Fusarium group, Alternaria group, Aspergillus group, and other genus groups based on positive results from biological cultures. Key clinical parameters, including best-corrected visual acuity (BCVA), maximum ulcer lesion diameter, and healing grades, were assessed and compared at baseline (pre-treatment), on postoperative day 3, and at postoperative week 3.

RESULTS

The study demonstrated that the BCVA (LogMAR) of all patients revealed no significant differences at postoperative day 3 (F = 2.54, p = 0.063) and week 3 (F = 1.86, p = 0.143). Although BCVA improved to varying degrees compared to preoperative levels, the changes were not statistically significant (p > 0.05). After treatment with LTP combined with pharmacotherapy across all four groups, an average of 53 patients (69.74%) achieved grade I healing, with the group effect being nonsignificant (F = 2.85, p = 0.071), while the effect of time post-treatment was significant (F = 67.85, p < 0.001). Additionally, the corneal scar diameter at postoperative week 3 was significantly smaller compared to the preoperative lesion diameter (p < 0.05). Multiple comparisons revealed significant differences in scar diameter among patients with grade I healing at postoperative week 3 (F = 3.48, p = 0.023), with notable differences observed between the Alternaria and Fusarium groups (p = 0.017). The average rate of grade III healing, defined by the occurrence of corneal perforation and/or the need for therapeutic penetrating keratoplasty, was 7.89%.

CONCLUSION

Low-temperature plasma ablation demonstrates effective therapeutic outcomes for FK caused by various pathogens that are unresponsive to pharmacological treatments, with no significant complications.

kexB Gene Correlates With Aspergillus flavus Keratitis Severity: A Whole-Genome Analysis

Purpose

Fungal keratitis caused by Aspergillus flavus (A. flavus) can result in severe inflammation and corneal stromal melting, leading to visual impairment. This study aimed to identify virulent genes correlated with the severity of A. flavus keratitis using whole-genome sequencing.

Methods

Whole-genome sequencing of 21 clinical A. flavus strains from cornea was performed to elucidate the pathogenesis of A. flavus in infectious keratitis, followed by pan-genome analysis and virulence analysis. To further understand the results from the previous analyses, growth phenotypes and virulence effect of mutant strains were validated experimentally, including the spore counting, growth pattern under different conditions, and clinical and pathological evaluation of A. flavus keratitis in mice models.

Results

The A. flavus pan-genome was composed of 17,326 gene clusters with a core genome of 5378 (31.0% of the pan-genome) orthogroups in all 21 isolates. Virulence gene analysis revealed 183 genes contributing to A. flavus pathogenesis and mutation of the kexB gene was associated with the severity of keratitis. The kexB mutant (ΔkexB) strains showed significantly reduced conidia formation and lower growth rates in the presence of the cell-wall perturbing agents. Further, the mice models validated that clinical score, and corneal perforation rates significantly decreased in the group infected by ΔkexB strains. Infiltration of immune cells, gene expression of cytokines, and matrix metalloproteinase (MMP) were also decreased in the mutant group.

Conclusions

The role of kexB gene in A. flavus keratitis was identified through whole-genome sequencing. Its mutation impairs conidia formation, cell wall integrity, and invasion, leading to milder clinical symptoms.

Role of MYO1F in neutrophil and macrophage recruitment and pro-inflammatory cytokine production in Aspergillus fumigatus keratitis

PURPOSE

Myosin 1f (Myo1f), an unconventional long-tailed class Ⅰ myosin, plays significant roles in immune cell motility and innate antifungal immunity. This study was aimed to assess the expression and role of Myo1f in Aspergillus fumigatus (AF) keratitis.

METHODS

Myo1f expression in the corneas of mice afflicted with AF keratitis and in AF keratitis-related cells was assessed using protein mass spectrometry, quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and immunofluorescence. Myo1f expression following pre-treatment with inhibitors of dendritic cell-associated C-type lectin-1 (Dectin-1), Toll-like receptor 4 (TLR-4), and lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) was also examined. In AF keratitis mouse models, Myo1f small interfering RNA (siRNA) was administered via subconjunctival injection to observe disease progression, inflammatory cell recruitment, and protein production using slit lamp examination, immunofluorescence, hematoxylin-eosin (HE) staining, and western blotting.

RESULTS

Myo1f expression was upregulated in both AF keratitis mouse models and AF keratitis-related cells. Dectin-1, TLR-4, and LOX-1 were found to be essential for the production of Myo1f in response to the infection with AF. In mice with AF keratitis, knockdown of Myo1f reduced disease severity, decreased the recruitment of neutrophils alongside macrophages to inflammatory areas, suppressed the myeloid differentiation factor 88 (MyD88)/ nuclear factor-kappaB (NF-κB) signaling pathway, and decreased the production of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, along with IL-6. Additionally, Myo1f was associated with apoptosis and pyroptosis in mice with AF keratitis.

CONCLUSIONS

These findings demonstrated that Myo1f contributed to the recruitment of neutrophils and macrophages, the production of pro-inflammatory cytokines, and was associated with apoptosis and pyroptosis during AF keratitis.

Multifunctional natamycin modified chondroitin sulfate eye drops with anti-inflammatory, antifungal and tissue repair functions possess therapeutic effects on fungal keratitis in mice

Fungal keratitis (FK) is recognized as a stubborn ocular condition, caused by intense fungal invasiveness and heightened immune reaction. The glycosaminoglycan chondroitin sulfate exhibits properties of immunomodulation and tissue regeneration. In prior investigations, oxidized chondroitin sulfate (OCS) ameliorated the prognosis of FK in murine models. To further improve the curative efficacy, we used the antifungal drug natamycin to functionalize OCS and prepared oxidized chondroitin sulfate-natamycin (ON) eye drops. The structure of ON was characterized by FTIR, UV-vis, and XPS, revealing that the amino group of natamycin combined with the aldehyde group in OCS through Schiff base reaction. Antifungal experiments revealed that ON inhibited fungal growth and disrupted the mycelium structure. ON exhibited exceptional biocompatibility and promoted the proliferation of corneal epithelial cells. Pharmacokinetic analysis indicated that ON enhanced drug utilization by extending the mean residence time in tears. In murine FK, ON treatment reduced the clinical score and corneal fungal load, restored corneal stroma conformation, and facilitated epithelial repair. ON effectively inhibited neutrophil infiltration and decreased the expression of TLR-4, LOX-1, IL-1β, and TNF-α. Our research demonstrated that ON eye drops achieved multifunctional treatment for FK, including inhibiting fungal growth, promoting corneal repair, enhancing drug bioavailability, and controlling inflammatory reactions.

Anti-Inflammatory Efficacy of Nanobody Specific to β-Glucan on a Fungal Cell Wall in a Murine Model of Fungal Keratitis

Purpose: to explore the anti-inflammatory effects of a nanobody (Nb) specific to β-glucan on fungal keratitis (FK). Methods: in order to verify the therapeutic and anti-inflammatory efficacy of Nb in FK, the severity of inflammation was assessed with inflammatory scores, hematoxylin-eosin (HE) staining, and myeloperoxidase (MPO) assays. In corneas of mice of FK model and human corneal epithelial cells stimulated by fungal hyphae, real-time reverse transcriptase polymerase chain reaction, Western blot, and enzyme-linked immunosorbent assay were used to detect the expression levels of inflammatory cytokines and pattern recognition receptors (PRRs). In vivo, macrophages and neutrophils infiltration in the cornea stroma was detected by immunofluorescence (IFS) staining. Results: In murine models infected with Aspergillus fumigatus (A. fumigatus), Nb treatment could reduce the inflammatory scores. HE staining and MPO results showed Nb significantly alleviated corneal edema and reduced inflammatory cell infiltration 3 days post-infection. In addition, the expression levels of LOX-1 and Dectin-1 were significantly decreased in the Nb group in vivo. The expression of chemokines CCL2 and CXCL2 also decreased in the Nb group. Compared with the PBS group, the number of macrophages and neutrophils in the Nb group was significantly decreased, which was shown in IFS results. Moreover, Nb attenuated the expression of Dectin-1, LOX-1, and inflammatory mediators, including IL-6 and IL-8 in vitro. Conclusion: our study showed that Nb could alleviate FK by downregulating the expression of PRRs and inflammatory factors as well as reducing the infiltration of macrophages and neutrophils.

Ebselen improves fungal keratitis through exerting anti-inflammation, anti-oxidative stress, and antifungal effects

Fungal keratitis is a severely vision-threatening corneal infection, where the prognosis depends on both fungal virulence and host immune defense. Inappropriate host responses can induce substantial inflammatory damage to the cornea. Therefore, in the treatment of fungal keratitis, it is important to concurrently regulate the immune response while efforts are made to eliminate the pathogen. Ebselen is a widely studied organo-selenium compound and has been demonstrated to have antifungal, antibacterial, anti-inflammatory, and oxidative stress-regulatory properties. The effectiveness of ebselen for the treatment of fungal keratitis remains unknown. In this study, ebselen was demonstrated to produce a marked inhibitory effect on Aspergillus fumigatus (A. fumigatus), including spore germination inhibition, mycelial growth reduction, and fungal biofilm disruption. The antifungal activity of ebselen was related to the cell membrane damage caused by thioredoxin (Trx) system inhibition-mediated oxidative stress. On the contrary, ebselen enhanced the antioxidation of Trx system in mammalian cells. Further, ebselen was proven to suppress the expressions of inflammatory mediators (IL-1β, IL-6, TNF-α, COX-2, iNOS, and CCL2) and reduce the production of oxidative stress-associated indicators (ROS, NO, and MDA) in fungi-stimulated RAW264.7 cells. In addition, ebselen regulated PI3K/Akt/Nrf2 and p38 MAPK signaling pathways, which contributed to the improvement of inflammation and oxidative stress. Finally, we verified the therapeutic effect of ebselen on mouse fungal keratitis. Ebselen improved the prognosis and reduced the fungal burden in mouse corneas. Expressions of inflammatory mediators, as well as the infiltration of macrophages and neutrophils in the cornea were also obviously decreased by ebselen. In summary, ebselen exerted therapeutic effects by reducing fungal load and protecting host tissues in fungal keratitis, making it a promising treatment for fungal infections.

The Effectiveness and Safety of Intravitreal Injections of Voriconazole in the Treatment of Fungal Endophthalmitis: A Systematic Review

Background: Fungus endophthalmitis is a rare and serious infection that is treated with systemic and topical antifungal drugs. There is no clear consensus on the treatment of fungal endophthalmitis with intravitreal injections (IVIs) of voriconazole. This systematic review aims to summarize the literature on IVIs of voriconazole for fungal endophthalmitis. Methods: We conducted a systematic review of the literature to determine the effectiveness and safety of IVIs of voriconazole in the treatment of fungal endophthalmitis. We searched databases such as PubMed and Embase using the following search terms "Endophthalmitis" AND "Intravitreal Injections" AND "Voriconazole" with date limits of January 1, 1900, to December 31, 2022. We included all reports on humans, which described clinical outcomes of IVIs of voriconazole in the treatment of fungal endophthalmitis, including randomized controlled trials (RCTs) and case series. A descriptive synthesis of the data was conducted with a pooling of data for interventions. Results: One RCT and 21 retrospective studies were analyzed in this review. In these reports, a wide range of heterogeneous treatment regimens was used, including IVI in combination with other drugs, systemic therapy in combination with other agents, and surgery. Combined with other treatments, intravitreal voriconazole results in a favorable anatomical and clinical cure that was well tolerated. Conclusions: Reports on IVIs of voriconazole for fungal endophthalmitis demonstrate a heterogeneous approach to treatment. Of these, IVIs of voriconazole in anatomical and clinical outcomes appeared to be highly effective, although more data on its safety are needed.

Plumbagin inhibits fungal growth, HMGB1/LOX-1 pathway and inflammatory factors in A. fumigatus keratitis

To investigate the anti-inflammatory and antifungal effects of plumbagin (PL) in Aspergillus fumigatus (A. fumigatus) keratitis, the minimum inhibitory concentration (MIC), time-killing curve, spore adhesion, crystal violet staining, calcium fluoride white staining, and Propidium Iodide (PI) staining were employed to assess the antifungal activity of PL in vitro against A. fumigatus. The cytotoxicity of PL was assessed using the Cell Counting Kit-8 (CCK8). The impact of PL on the expression of HMGB1, LOX-1, TNF-α, IL-1β, IL-6, IL-10 and ROS in A. fumigatus keratitis was investigated using RT-PCR, ELISA, Western blot, and Reactive oxygen species (ROS) assay. The therapeutic efficacy of PL against A. fumigatus keratitis was assessed through clinical scoring, plate counting, Immunofluorescence and Hematoxylin-Eosin (HE) staining. Finally, we found that PL inhibited the growth, spore adhesion, and biofilm formation of A. fumigatus and disrupted the integrity of its cell membrane and cell wall. PL decreased IL-6, TNF-α, and IL-1β levels while increasing IL-10 expression in fungi-infected mice corneas and peritoneal macrophages. Additionally, PL significantly attenuated the HMGB1/LOX-1 pathway while reversing the promoting effect of Boxb (an HMGB1 agonist) on HMGB1/LOX-1. Moreover, PL decreased the level of ROS. In vivo, clinical scores, neutrophil recruitment, and fungal burden were all significantly reduced in infected corneas treated with PL. In summary, the inflammatory process can be inhibited by PL through the regulation of the HMGB-1/LOX-1 pathway. Simultaneously, PL can exert antifungal effects by limiting fungal spore adhesion and biofilm formation, as well as causing destruction of cell membranes and walls.