Pythium insidiosum: insights into biofilm formation and antibiofilm activity of antifungal drugs

In this study, we investigate the ability of Pythium insidiosum to form biofilms across various substrates and the antibiofilm efficacy of 8-hydroxyquinoline derivatives (8-HQs). Biofilms of P. insidiosum were cultured on polystyrene plates, contact lenses, and horsehair. We provide the first evidence of P. insidiosum's biofilm-forming capability, thus considerably expanding our understanding of its transmission and pathogenesis. Our results demonstrate that 8-HQs effectively inhibit biofilm formation and eradicate pre-existing biofilms, underscoring their potential as a novel treatment strategy for pythiosis, a disease currently lacking a gold-standard treatment. This finding has particular relevance for ocular pythiosis associated with contact lens usage and potential infection sources in animals. Our results contribute to the scientific knowledge base and directly impact innovative therapeutic interventions' development.

Global prevalence of free-living amoebae in solid matrices - A systematic review with meta-analysis

The ubiquitous free-living amoebae (FLA) are microorganisms of significant medical, sanitary, and ecological importance. However, their characterization within solid matrices such as soil, dust, sediment, mud, sludge, and compost remain to be systematized. In this study, we conducted a systematic review with meta-analysis to explore the global distribution of FLA in solid matrices. From the analysis of 104 out of 4,414 scientific articles retrieved from different databases, it was found that the general global prevalence of FLA in solid matrices was of 55.13% (95% confidence interval (CI) 49.32-60.94). Specifically, FLA prevalence was high in soil (72.40%, 95% CI 69.08-75.73), sediment (57.91%, 95% CI 50.01-65.81), mud (52.90%, 95% CI 24.01-81.78), dust (48.60%, 95% CI 43.00-54.19), and sewage sludge (40.19%, 95% CI 30.68-49.70). In aerosols it was comparatively lower (17.21%, 95% CI 12.76-21.66). Acanthamoeba spp. (52.23%) and Hartmanella/Vermamoeba spp. (36.06%) were found to be more prevalent, whereas Naegleria spp. (34.98%) and Balamuthia spp. (27.32%) were less prevalent. The distribution of the highest global prevalence values for species of Acanthamoeba spp., considering different publication periods of the studies, is as follows: A. hatchetti (51.46%), A. rhysodes (47.49%), A. polyphaga (36.37%), A. culbertsoni (34.31%), A. castellanii (34.21%), and A. lenticulata (32.82%). For other FLA species, the distribution is: Hartmannella/Vermamoeba vermiformis (91.57%), Naegleria fowleri (42.32%), Naegleria gruberi (32.39%), and Balamuthia mandrillaris (25%). The most prevalent Acanthamoeba genotypes were T4 (33.38%) and T3 (23.94%). Overall, the global prevalence of FLA in solid matrices is as high as or greater than that reported in water by previous systematic reviews. Thus, actions aimed at reducing exposure to FLA or exploring their ecological dynamics should consider not only water but also the various solid matrices. The finding outlined here can provide valuable insights for such actions, e.g., informing on the level of exposure to FLA, or on the microbial biodiversity of specific environmental compartments.

In vitro pharmacokinetics/pharmacodynamics modeling and efficacy against systemic candidiasis in Drosophila melanogaster of a bisaryloxypropanamine derivative

The number of deaths due to systemic fungal infections is increasing alarmingly, which is aggravated by the limitations of traditional treatments and multidrug resistance. Therefore, the research and development of new therapeutic options against pathogenic fungi is an urgent need. To evaluate the fungicidal activity of a synthetic compound, 1,3-bis-(3,4-dichlorophenoxy)propan-2-aminium chloride (2j), through time-kill studies and pharmacokinetics/pharmacodynamics (PK/PD) modeling. The protective effect of the compound was also evaluated using the Drosophila melanogaster minihost model of candidiasis. Mathematical modeling of time-kill data of compound 2j was performed to obtain PD characteristics. Additionally, Toll-deficient D. melanogaster flies were infected with a Candida albicans strain and treated with 2j. We observed that compound 2j demonstrated a time- and dose-dependent fungicidal effect against Candida spp. and dermatophytes, even at low concentrations, and rapidly achieved kill rates reaching the maximum effect in less than one hour. The efficacy of the compound against systemic candidiasis in D. melanogaster flies was comparable to that achieved by fluconazole. These results support the potential of compound 2j as a systemic antifungal agent candidate and serve as a starting point for further studies involving mammalian animal models.

Antifungal activity and toxicological parameters of 8-hydroxyquinoline-5-sulfonamides using alternative animal models

AIM

The purpose of this study was to evaluate the antifungal activity and toxicological parameters of 8-hydroxyquinoline derivatives PH151 and PH153 using alternative animal models, to understand their behaviour when subjected to in vivo experiments.

METHODS AND RESULTS

We used Toll-deficient Drosophila melanogaster to test the protective effect of compounds against Candida albicans infection. Toxicological parameters were investigated in chicken and zebrafish embryos. PH151 and PH153 showed low toxicity and the treated flies with these compounds had a significantly higher survival rate than untreated flies after 7 days of infection. The compounds did not cause interruption of chicken embryogenesis. Zebrafish embryos exposed to compounds showed dose-dependent toxicity.

CONCLUSIONS

The data supported the potential of PH151 and PH153 for the treatment of systemic candidiasis and demonstrated to be appropriate drug candidates for further studies using mammalian models.

SIGNIFICANCE AND IMPACT OF THE STUDY

The increased incidence of Candida infections resistant to antifungals currently available requires acceleration of the discovery of new agents with properties of inhibiting this fungal pathogen. In this study, we have described the antifungal potential and toxicity of two 8-hydroxyquinoline derivatives using in vivo alternative models, and the results confirm their potential to be developed as new drug candidates.

New insights on evolutionary aspects of Pythium insidiosum and other peronosporaleans

BACKGROUND

The evolution of pathogenic mechanisms is a major challenge, which requires a thorough comprehension of the phylogenetic relationships of pathogens. Peronosporaleans encompasses a heterogeneous group of oomycetes that includes some animal/human pathogens, like Pythium insidiosum.

OBJECTIVE

We analysed here the phylogenetic positioning and other evolutionary aspects related to this species and other peronosporaleans, using a multi-locus approach with one mitochondrial and three nuclear genes.

METHODOLOGY

Phylogenetic patterns of 55 oomycetes were inferred by maximum likelihood and Bayesian analysis, and a relaxed molecular clock method was applied to infer the divergence time of some peronosporaleans branches.

RESULTS

Pythium insidiosum was monophyletic with a major and polytomous clade of American isolates; however, Pythium spp. was found to be paraphyletic with Phytopythium sp. and Phytophthora spp. In general, peronosporaleans subdivided into four lineages, one of which evidenced a close relationship of P insidiosum, P aphanidermatum and P arrhenomanes. This lineage diverged about 63 million years ago (Mya), whereas P insidiosum diversified at approximately 24 Mya. The divergence of American and Thai isolates seems to have occurred at approximately 17 Mya, with further American diversification at 2.4 Mya.

CONCLUSION

Overall, this study clarifies the phylogenetic relationships of P insidiosum regarding other peronosporaleans in a multi-locus perspective, despite previous claims that phylogenomic analyses are needed to accurately infer the patterns and processes related to the evolution of different lineages in this group. Additionally, this is the first time that a molecular clock was applied to study the evolution of P insidiosum.

Intradermal injection of Pythium insidiosum protein antigens for improved diagnosis and treatment of pythiosis in an experimental model

The oomycetous pathogen Pythium insidiosum is the causative agent of pythiosis, a life-threatening disease that affects animals and humans. This infectious disease is difficult to treat, and early and accurate diagnosis is critical for effective treatment. In this sense, this study aimed to evaluate the intradermal (ID) injection of P. insidiosum protein antigens (PiPA) for the diagnosis and treatment of pythiosis using an experimental model. For diagnostic purposes, PiPA were injected by the ID route in the following groups of rabbits: (a) control; (b) previously immunized with PiPA injected by the subcutaneous (SC) route; and (c) infected with P. insidiosum zoospores. For treatment purposes, rabbits with pythiosis were also treated with PiPA by the ID or SC routes. Mean induration sizes were different at 24 h and 72 h readings when compared to the control group. Sensitivity of the protocol was 100% at 24 h and 80% at 72 h, with 100% specificity in both readings. PiPA treatment using ID or SC routes did not result in significant differences in lesion sizes and cure rates; however, serum levels of interferon-gamma were higher in SC route. This study demonstrates the applicability of PiPA ID for diagnosis and treatment of pythiosis in an experimental model.

In vitro interactions of azoles and echinocandins against clinical strains of Aspergillus flavus

Combinations of an azole (itraconazole, voriconazole, or posaconazole) with an echinocandin (caspofungin, micafungin, or anidulafungin) were tested against 20 clinical isolates of Aspergillus flavus according to EUCAST guidelines. The interactions were determined using two endpoints-minimal effective concentration (MEC) and minimal inhibitory concentration (MIC)-via calculation of the fractional inhibitory concentration (FIC) index. A higher prevalence of synergistic interactions was observed for MIC, whereas indifference was the most frequent outcome according to MEC among the 20 strains. Combined treatment of A. flavus with these two important classes of antifungals should be explored further in in vivo studies.

Bite Caused by the Assassin Bug Zelus Fabricius, 1803 (Hemiptera; Heteroptera: Reduviidae) in a Human

A 47-y-old man was bitten by a reduviid bug from the Zelus Fabricius, 1803 genus, which was hidden inside a rubber-coated boot. The bite caused immediate and sharp pain, followed by local edema and constant pruritus for 15 d. Pain and fever within the first 24 h were managed with analgesics as needed, and resolution was complete and without sequelae after 21 d.

In vitro susceptibility of chromoblastomycosis agents to antifungal drugs: A systematic review

Chromoblastomycosis (CBM) is a chronic granulomatous mycosis caused by dematiaceous fungi that affects cutaneous and subcutaneous tissues. The standard antifungal drug for treatment is itraconazole, followed by terbinafine. However, cure rates vary from 15% to 80% when these drugs are used as monotherapy. A systematic review of the in vitro susceptibility of CBM agents to antifungal drugs, alone and in combination, was conducted using the Cochrane methodology. Forty-seven search terms were included in the PICOS method of searching electronic databases. The search resulted in 35 studies, of which 8 evaluated antifungal drugs in combination. Based on minimum inhibitory concentrations (MICs), posaconazole, terbinafine, itraconazole and voriconazole were, in descending order, the most effective antifungal drugs against CBM agents in vitro. In drug combination studies, only terbinafine-voriconazole and itraconazole-caspofungin showed 100% synergy for Fonsecaea pedrosoi, Exophiala jeanselmei and Phialophora verrucosa. However, none of the combinations studied showed antagonism.

In vitro antifungal susceptibility of clinical and environmental isolates of Aspergillus fumigatus and Aspergillus flavus in Brazil

The in vitro susceptibility of 105 clinical and environmental strains of Aspergillus fumigatus and Aspergillus flavus to antifungal drugs, such as amphotericin B, azoles, and echinocandins was evaluated by the broth microdilution method proposed by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Following the EUCAST-proposed breakpoints, 20% and 25% of the clinical and environmental isolates of A. fumigatus, respectively, were found to be resistant to itraconazole (Minimal Inhibitory Concentration, MIC > 2.0 mg/L). Voriconazole showed good activity against A. fumigatus and A. flavus strains, except for one clinical strain of A. fumigatus whose MIC was 4.0 mg/L. Posaconazole (≤0.25 mg/L) also showed appreciable activity against both species of Aspergillus, except for six A. fumigatus strains with relatively higher MICs (0.5 mg/L). The MICs for Amphotericin B ranged from 0.06 to 1.0 mg/L for A. fumigatus, but were much higher (0.5–8.0 mg/L) for A. flavus. Among the echinocandins, caspofungin showed a geometric mean of 0.078 and 0.113 against the clinical and environmental strains of A. flavus, respectively, but had elevated minimal effective concentrations (MECs) for seven of the A. fumigatus strains. Anidulafungin and micafungin exhibited considerable activity against both A. fumigatus and A. flavus isolates, except for one environmental isolate of A. fumigatus that showed an MEC of 1 mg/L to micafungin. Our study proposes that a detailed investigation of the antifungal susceptibility of the genus Aspergillus from different regions of Brazil is necessary for establishing a response profile against the different classes of antifungal agents used in the treatment of aspergillosis.

Syzygium cumini seed extract ameliorates adenosine deaminase activity and biochemical parameters but does not alter insulin sensitivity and pancreas architecture in a short-term model of diabetes

BACKGROUND

The effects of the aqueous seed extract of Syzygium cumini (ASc) in a short-term model of diabetes in rats are little explored. The present study was designed to evaluate the effect of the ASc on adenosine deaminase (ADA) activity and on biochemical and histopathological parameters in diabetic rats.

METHODS

ASc (100 mg/kg) was administered for 21 days in control and streptozotocin (STZ)-induced (60 mg/kg) diabetic rats. ADA activity, lipoperoxidation (cerebral cortex, kidney, liver and pancreas) and biochemical (serum) and histopathological (pancreas) parameters were evaluated.

RESULTS

The main findings in this short-term model of Diabetes mellitus (DM) were that the ASc (i) significantly reverted the increase of ADA activity in serum and kidney; (ii) ameliorated the lipoperoxidation in the cerebral cortex and pancreas of the diabetic group; (iii) demonstrated hypolipidemic and hypoglycemic properties and recovered the liver glycogen; and iv) prevented the HOMA-IR index increase in the diabetic group. Therefore, the ASc can be a positive factor for increasing the availability of substrates with significant protective actions, such as adenosine. Moreover, by maintaining glycogen and HOMA-IR levels, the extract could modulate the hyperglycemic state through the direct peripheral glucose uptake.

CONCLUSIONS

Our data revealed that the short-term treatment with ASc has an important protective role under pathophysiological conditions caused by the early stage of DM. These results enhance our understanding of the effect of the ASc on the purinergic system in DM.

Cytoprotective and genoprotective effects of β-glucans against aflatoxin B₁-induced DNA damage in broiler chicken lymphocytes

The polysaccharide β-glucan presents beneficial effects on the immune system, although the mechanisms of the immunomodulatory effect remain poorly understood. The potential cytoprotective and genoprotective effects of β-glucans were evaluated in broiler chicken lymphocytes exposed to increasing concentrations of aflatoxin B₁ (AFB₁) and/or β-glucans. AFB₁ significantly decreased cell viability at the concentrations of 10 and 20 μg/ml at 72 h of incubation (p<0.01 and p<0.001, respectively). Moreover, the AFB₁ concentrations of 1, 10 and 20 μg/ml increased DNA fragmentation levels at 24 h (p<0.001). Conversely, lymphocyte death was prevented by β-glucans at the concentrations of 1% and 10%, indicating a cytoprotective effect. Reactive oxygen species levels were increased in the cells treated with 20 μg/ml AFB₁ at 24 h (p<0.05) and 10% β-glucans with or without AFB₁ at 24, 48 and 72 h of incubation (p<0.001). DNA damage increased by more than 100% in AFB₁-treated lymphocytes when compared to control group. β-glucans at 1% was able to fully revert the AFB₁-induced lymphocyte DNA damage, indicating a genoprotective effect and maintaining DNA integrity. In conclusion, β-glucans showed in vitro dose-dependent cytoprotective and genoprotective effects in broiler chicken lymphocytes exposed to AFB₁.

In vitro susceptibility of Conidiobolus lamprauges recovered from sheep to antifungal agents

Data regarding the susceptibility of Conidiobolus lamprauges is limited and there is no consensus about the optimal treatment for infections caused by Conidiobolus spp. In this context, the objective of this study was to evaluate the in vitro susceptibility of six C. lamprauges strains isolated from sheep conidiobolomycosis to amphotericin B, ketoconazole, fluconazole, itraconazole, posaconazole, voriconazole, anidulafungin, caspofungin, micafungin, flucytosine, and terbinafine using the CLSI M38-A2 microdilution technique. Terbinafine was the most active (MIC range <0.06-0.5 μg/mL). Resistance or reduced susceptibility was observed for amphotericin B and azole and echinocandin antifungals. Additional studies are necessary to determine the therapeutic potential of terbinafine as monotherapy or in combination therapy with other antifungals.

Differential effects of organic and inorganic selenium compounds on adenosine deaminase activity and scavenger capacity in cerebral cortex slices of young rats

Selenium (Se) has anti-inflammatory and antioxidant properties and is necessary for the development and normal function of the central nervous system. This study was aimed to compare the in vitro effects of 3-methyl-1-phenyl-2-(phenylseleno)oct-2-en-1-one (C21H2HOSe; organoselenium) and sodium selenate (inorganic Se) on adenosine deaminase (ADA) activity, cell viability, lipid peroxidation, scavenger of nitric oxide (NO) and nonprotein thiols (NP-SH) content in the cerebral cortex slices of the young rats. A decrease in ADA activity was observed when the slices were exposed to organoselenium at the concentrations of 1, 10 and 30 µM. The same compound showed higher scavenger capacity of NO than the inorganic compound. Inorganic Se was able to protect against sodium nitroprusside-induced oxidative damage and increased the NP-SH content. Both the compounds displayed distinctive antioxidant capacities and were not cytotoxic for the cerebral cortex slices in the conditions tested. These findings are likely to be related to immunomodulatory and antioxidant properties of this compound.

E-ADA activity in lymphocytes of an experimental model of pythiosis treated with immunotherapy

Pythiosis is a life-threatening disease caused by the oomycete Pythium insidiosum. Some authors have suggested the involvement of a Th2-like immune response in the infected host, which leads to extensive tissue damage. The switch from a Th2 to a Th1 response pattern is one hypothesis to explain the curative properties of immunotherapy. Taking into account the importance of immunotherapy for pythiosis treatment and the contribution of adenine nucleotides in the immunoregulation of the host, we evaluated the ecto-adenosine deaminase (E-ADA; EC 3·5.4·4) activity in lymphocytes from rabbits inoculated with P. insidiosum. Rabbits were inoculated with 1 milliliter of zoospores subcutaneously injected into the lateral thorax; after developing lesions, the rabbits received eight doses of immunotherapy. E-ADA activity was measured in lymphocytes and the adenine nucleotides and adenosine levels were quantitatively determined in serum. Rabbits with characteristic lesions of pythiosis showed a decreased E-ADA activity (82·36%), a decreased adenosine triphosphate concentration (54·04%) and a higher adenosine concentration (2·51 fold), when compared with controls, after 28 days of inoculation. However, after the immunotherapy, the rabbits showed an increase in the E-ADA activity when compared with control (78·62%), contributing for the change in the immune response. Our results reinforce the hypothesis that the change from a Th2 to a Th1 immune response with the participation of the purinergic system could be responsible for the curative properties of immunotherapy.

Biologia da mosca Phaenicia sericata em diferentes substratos

Dípteros da espécie Phaenicia sericata foram capturadas e mantidas em gaiolas teladas para avaliação de seu ciclo biológico e definição do melhor substrato para postura e desenvolvimento larval em temperatura e umidade constante (27°C e 80% UR). Foram utilizados quatro substratos em decomposição; carne bovina, de frango e de peixe bem como fígado bovino. Os três primeiros substratos não diferiram estatisticamente entre si quanto à preferência das moscas e no fígado não houve postura. Os mesmos substratos foram utilizados para alimentação das larvas, sendo observado não haver interferência no período larval. Observou-se também que a cópula ocorreu cinco dias após a pupação e a postura seis dias após a cópula. A longevidade das moscas adultas foi em média de 37 dias quando alimentadas com mel e água. Com base nesses resultados observou-se que o ciclo biológico da P. sericata foi em média de 51 dias em laboratório.