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.

Clioquinol and 8-hydroxyquinoline-5-sulfonamide derivatives damage the cell wall of Pythium insidiosum.

AIMS: To evaluate the antimicrobial activity and to determine the pharmacodynamic characteristics of three 8-hydroxyquinoline derivatives (8-HQs) against Pythium insidiosum, the causative agent of pythiosis. METHODS AND RESULTS: Antimicrobial activity was tested by broth microdilution and MTT assays. The antimicrobial mode of action was investigated using sorbitol protection assay, ergosterol binding assay, and scanning electron microscopy. Clioquinol, PH151, and PH153 were active against all isolates, with MIC values ranging from 0.25 to 2 µg ml-1. They also showed a time- and dose-dependent antimicrobial effect, damaging the P. insidiosum cell wall. CONCLUSIONS: Together, these results reinforce the potential of 8-HQs for developing new drugs to treat pythiosis.

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.

Efficacy of miltefosine therapy against subcutaneous experimental pythiosis in rabbits.

We evaluated the in vitro activity of miltefosine against 29 Pythium spp. and the in vivo therapeutic response of 2mg/kg/day of miltefosine given orally to rabbit with pythiosis induced experimentally. The MICs (in µg/mL) of miltefosine was medium-dependent and ranged from 0.5 to 2 and 32-64 on RPMI 1640 and Mueller Hinton broth, respectively. The treatment with miltefosine demonstrated significantly lower subcutaneous lesion areas compared to the control group but was not sufficient for the complete remission of the lesions. This study indicates that miltefosine has limited efficacy against pythiosis and furthers in vitro and in vivo studies are necessary to determine the possible potential of this drug in the treatment of pythiosis.

In vitro activity of carvacrol and thymol combined with antifungals or antibacterials against Pythium insidiosum.

We describe the in vitro activities of the combinations of carvacrol and thymol with antibiotics (azithromycin, clarithromycin, minocycline and tigecycline) and antifungal agents (amphotericin B, caspofungin, itraconazole and terbinafine) against 23 isolates of the oomycete Pythium insidiosum. The assays were based on the M38-A2 technique and checkerboard microdilution. Based on the mean FICI values, the main synergies observed were combinations of carvacrol+itraconazole and thymol+itraconazole (96%), thymol+clarithromycin (92%), carvacrol+clarithromycin (88%), thymol+minocycline (84%), carvacrol+minocycline (80%), carvacrol+azithromycin (76%), thymol+azithromycin (68%), carvacrol+tigecycline (64%) and thymol+tigecycline (60%). In conclusion, we found that combinations of carvacrol or thymol with these antimicrobial agents might provide effective alternative treatments for cutaneous pythiosis due to their synergistic interactions. Future in vivo experiments are needed to elucidate the safety and therapeutic potential of these combinations.

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

The polysaccharide ß-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 ß-glucans were evaluated in broiler chicken lymphocytes exposed to increasing concentrations of aflatoxin B1 (AFB1) and/or ß-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 ß-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% ß-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. ß-glucans at 1% was able to fully revert the AFB1-induced lymphocyte DNA damage, indicating a genoprotective effect and maintaining DNA integrity. In conclusion, ß-glucans showed in vitro dose-dependent cytoprotective and genoprotective effects in broiler chicken lymphocytes exposed to AFB1.

Micafungin alone and in combination therapy with deferasirox against Pythium insidiosum.

This study evaluated the in vitro and in vivo activity of micafungin alone and in combination with the iron chelator deferasirox against Pythium insidiosum. Micafungin showed a poor in vitro activity when it was used alone, but synergistic interactions were observed for 88.2% of the strains when the drug was combined with deferasirox. Smaller lesions were observed in infected rabbits receiving the combination therapy, although it favored disease dissemination to the lungs. The present results show that micafungin alone is ineffective against P. insidiosum, and the combination micafungin-deferasirox might have deleterious effects for the host.

Efficacy of a Brazilian calcium montmorillonite against toxic effects of dietary aflatoxins on broilers reared to market weight.

1. The protective effect of a natural Brazilian calcium montmorillonite (CaMont) against aflatoxins was studied in broiler chickens. 2. A total of 1056-d-old Cobb male broilers were housed in experimental pens (22 chickens per pen) for 42 d. Three levels of CaMont (0, 2.5 and 5 g/kg) and two levels of aflatoxins (0 and 3 mg/kg) were assayed. Each treatment had 8 replicate pens of 22 broiler chickens each. 3. Of all the chickens tested in the experiment, the ones treated with aflatoxins were the most adversely affected. CaMont treatment at concentrations of 2.5 and 5 g/kg improved body weight of chickens at 42 d of age by 13.3% and 22.7%, increased daily feed intake by 9.7% and 24.7%, and improved the productive efficiency index of chickens by 53% and 66.5%, respectively. 4. Dietary CaMont positively affected parameters such as weight of liver, heart and gizzard; however, serum potassium concentration decreased by 15.3% compared with that of chickens given only the aflatoxin-contaminated diet. 5. CaMont did not cause adverse effects in chickens that did not receive aflatoxins. 6. CaMont at pH 8.5 partially reduced the toxic effects of aflatoxins in broilers when included at levels of 2.5 and 5 g/kg in the diet.

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.

Iron chelation therapy as a treatment for Pythium insidiosum in an animal model.

OBJECTIVES: Iron plays an important role in the pathogenesis of Pythium insidiosum. Human pythiosis frequently occurs in iron-overloaded thalassaemic patients and experimentally infected animals develop iron deficiency anaemia. Therefore, we sought to determine the in vitro and in vivo activities of the iron chelator deferasirox against P. insidiosum. METHODS: In vitro, the MIC and minimum fungicidal concentration (MFC) values of deferasirox for 17 strains of P. insidiosum were determined in accordance with CLSI document M38-A2. In vivo studies were carried out in 20 inoculated rabbits divided into four groups: placebo, immunotherapy obtained from vortexed P. insidiosum cultures (14 day intervals), deferasirox (15 mg/kg/day) and a combination of immunotherapy and deferasirox. Five non-infected animals were used as controls. RESULTS: The MIC and MFC values of deferasirox for P. insidiosum ranged from 12.5 to 50 mg/L and from 50 to 100 mg/L, respectively. Treatment with deferasirox alone ameliorated anaemia and normalized the serum iron levels and hepatic iron concentration in the animals. However, the mean lesion size, although decreased, did not differ significantly from that in the placebo group. The results of immunotherapy plus iron chelation therapy were worse than those of immunotherapy alone. Moreover, the disease spread to the lung tissue in 5 out of 10 deferasirox-treated animals. CONCLUSIONS: Despite its limited in vitro and in vivo activity, deferasirox improved iron deficiency anaemia in P. insidiosum-infected rabbits. Further studies are needed to investigate the immunomodulatory properties observed in this study and the benefits and drawbacks of using iron-chelating drugs as an adjuvant therapy in pythiosis.

Insights into the pathophysiology of iron metabolism in Pythium insidiosum infections.

Pythium insidiosum causes life-threatening disease in mammals. Animals with pythiosis usually develop anemia, and most human patients are reported to have thalassemia and the major consequence of thalassemia, iron overload. Therefore, this study evaluated the iron metabolism in rabbits experimentally infected with P. insidiosum. Ten infected rabbits were divided into two groups: one groups received a placebo, and the other was treated with immunotherapy. Five rabbits were used as negative controls. The hematological and biochemical parameters, including the iron profile, were evaluated. Microcytic hypochromic anemia was observed in the infected animals, and this condition was more accentuated in the untreated group. The serum iron level was decreased, whereas the transferrin level was increased, resulting in low saturation. The level of stainable iron in hepatocytes was markedly decreased in the untreated group. A high correlation was observed between the total iron binding capacity and the lesion size, and this correlation likely confirms the affinity of P. insidiosum for iron. The data from this study corroborate the previous implications of iron in the pathogenesis of pythiosis in humans and animals.

In vitro susceptibility of fluconazole-susceptible and -resistant isolates of Malassezia pachydermatis against azoles.

OBJECTIVES: The first aim of this study was to evaluate the in vitro efficacies of fluconazole, ketoconazole, itraconazole and voriconazole on M. pachydermatis growth inhibition. This study also evaluated M. pachydermatis azole cross-resistance, comparing wild clinical isolates and the same isolates with in vitro-induced fluconazole resistance. METHODS: Two techniques were used: (1) a broth microdilution method based on protocol M27-A3 from the Clinical and Laboratory Standards Institute to determine the minimum inhibitory concentration (MIC) and (2) the Fekete-Forgács method to induce fluconazole resistance in vitro. The isolates were divided into two groups: group 1 included fluconazole-susceptible clinical isolates (n=30) and group 2 contained the same isolates with in vitro-induced fluconazole resistance (n=30). RESULTS: The two groups exhibited differences in susceptibility (p<0.001). Group 1 isolates were susceptible to azoles: ketoconazole (MIC 0.01-1.0 µg/mL), itraconazole (MIC 0.01-1.0 µg/mL), voriconazole (MIC 0.01-4.0 µg/mL), and fluconazole (MIC 0.01-4.0 µg/mL). Group 2 isolates demonstrated a wider range of MICs to azoles: ITZ (MIC 0.06-64.0 µg/mL), KTZ (MIC 0.25-32.0 µg/mL), VRZ (MIC 2.0-128.0 µg/mL), and FLZ (MIC 64.0-128.0 µg/mL). CONCLUSIONS: It was shown that FLZ-resistant M. pachydermatis isolates exhibit cross-resistance to other azoles, reinforcing the importance of susceptibility tests as a guide for the therapeutic prescription of antifungals in medical and veterinary mycology.

Protective effects of Syzygium cumini seed extract against methylmercury-induced sistemic toxicity in neonatal rats.

Syzygium cumini (L.) Skeels (Sc) belongs to the medicinal plants with an important source of phenolic compounds. Sc has been shown to possess antioxidant and anti-inflammatory properties. Methylmercury (MeHg), a highly toxic environmental pollutant, induces oxidative stress and dysfunction in many cell types. This study was aimed to evaluate the effect of aqueous seed extract of Sc (ASc) on MeHg-induced toxicity in rats. Two-day-old rats (P2) received a single dose of MeHg (10 mg/kg) and two doses of ASc (0.9 mg/kg) per os. After two days, the effects of the treatment were investigated in the cerebral cortex, hippocampus, kidney, liver and urine samples. Our results demonstrated that N-acetyl-ß-D: -glucosaminidase (NAG) activity in the kidney and urine, the lipid peroxidation levels in the liver and kidney samples, as well as the adenosine deaminase (ADA) activity in the hippocampus, kidney and liver were higher in MeHg-group when compared to the control group. The administration of ASc reverted the toxic effects of MeHg. It is noteworthy to observe that the main compounds present in the ASc, as gallic acid (the major component), chlorogenic acid and rutin, might be the responsible for such benefit, since they were found to display antioxidant properties.

A suitable model for the utilization of Duddingtonia flagrans fungus in small-flock-size sheep farms.

Effective alternatives to anthelmintic treatment of nematode parasite infections of sheep are required because of the high prevalence of drug resistance. Within this context, the nematode-trapping fungus Duddingtonia flagrans has become a valuable component of various integrated control strategies. Toward this objective, a small quantity of lyophilized D. flagrans chlamydospores (10(6) spores per animal) was administered to sheep in a one-year plot study. Animals grazing on native pasture were divided into two homogeneous groups and were kept in 1-ha paddocks in the southern region of Brazil. The oral administration of chlamydospores led to a significant reduction (p<0.05) in the number of nematode eggs per gram of feces and in the larval availability on herbage (difference of 37.6%) in comparison to the control group. Control animals needed to be dewormed three times during the experiment, whereas the fungus-treated animals maintained a low parasite load, independent of seasonal variation. Although D. flagrans cannot serve as a panacea for nematode parasite control of livestock, it represents a significant advance toward rationalizing the use of endoparasitic drugs in small animals.

Antipyretic and antioxidant activities of 5-trifluoromethyl-4,5-dihydro-1H-pyrazoles in rats.

The objective of this study was to determine the effect of eight 5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-carboxyamidepyrazoles (TFDPs) on rat body temperature and baker's yeast-induced fever. TFDPs or vehicle (5% Tween 80 in 0.9% NaCl, 5 mL/kg) were injected subcutaneously and rectal temperature was measured as a function of time in 28-day-old male Wistar rats (N = 5-12 per group). Antipyretic activity was determined in feverish animals injected with baker's yeast (Saccharomyces cerevisiae suspension, 0.135 mg/kg, 10 mL/kg, ip). 3-Ethyl- and 3-propyl-TFDP (140 and 200 µmol/kg, respectively, 4 h after yeast injection) attenuated baker's yeast-induced fever by 61 and 82%, respectively. These two effective antipyretics were selected for subsequent analysis of putative mechanisms of action. We then determined the effects on cyclooxygenase-1 and -2 (COX-1 and COX-2) activities on 1,1-diphenyl-2-picrylhydrazyl (DPPH) oxidation in vitro, on tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß) levels and on leukocyte counts in the washes of peritoneal cavities of rats injected with baker's yeast. While 3-ethyl- and 3-propyl-TFDP did not reduce baker's yeast-induced increases of IL-1ß or TNF-α levels, 3-ethyl-TFDP caused a 42% reduction in peritoneal leukocyte count. 3-Ethyl- and 3-propyl-TFDP did not alter COX-1 or COX-2 activities in vitro, but presented antioxidant activity in the DPPH assay with an IC50 of 39 mM (25-62) and 163 mM (136-196), respectively. The data indicate that mechanisms of action of these two novel antipyretic pyrazole derivatives do not involve the classic inhibition of the COX pathway or pyrogenic cytokine release.

Antipyretic and antioxidant activities of 5-trifluoromethyl-4,5-dihydro-1H-pyrazoles in rats

The objective of this study was to determine the effect of eight 5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-carboxyamidepyrazoles (TFDPs) on rat body temperature and baker’s yeast-induced fever. TFDPs or vehicle (5 percent Tween 80 in 0.9 percent NaCl, 5 mL/kg) were injected subcutaneously and rectal temperature was measured as a function of time in 28-day-old male Wistar rats (N = 5-12 per group). Antipyretic activity was determined in feverish animals injected with baker’s yeast (Saccharomyces cerevisiae suspension, 0.135 mg/kg, 10 mL/kg, ip). 3-Ethyl- and 3-propyl-TFDP (140 and 200 μmol/kg, respectively, 4 h after yeast injection) attenuated baker’s yeast-induced fever by 61 and 82 percent, respectively. These two effective antipyretics were selected for subsequent analysis of putative mechanisms of action. We then determined the effects on cyclooxygenase-1 and -2 (COX-1 and COX-2) activities on 1,1-diphenyl-2-picrylhydrazyl (DPPH) oxidation in vitro, on tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) levels and on leukocyte counts in the washes of peritoneal cavities of rats injected with baker’s yeast. While 3-ethyl- and 3-propyl-TFDP did not reduce baker’s yeast-induced increases of IL-1β or TNF-α levels, 3-ethyl-TFDP caused a 42 percent reduction in peritoneal leukocyte count. 3-Ethyl- and 3-propyl-TFDP did not alter COX-1 or COX-2 activities in vitro, but presented antioxidant activity in the DPPH assay with an IC50 of 39 mM (25-62) and 163 mM (136-196), respectively. The data indicate that mechanisms of action of these two novel antipyretic pyrazole derivatives do not involve the classic inhibition of the COX pathway or pyrogenic cytokine release.

Influence of Trypanosoma evansi in blood, plasma, and brain cholinesterase of experimentally infected cats.

Changes in blood, plasma and brain cholinesterase activities in Trypanosoma evansi-infected cats were investigated. Seven animals were infected with 10(8) trypomastigote forms each and six were used as control. Animals were monitored for 56 days by examining daily blood smears. Blood samples were collected at days 28 and 56 post-inoculation to determine the activity of acetylcholinesterase (AChE) in blood and the activity of butyrylcholinesterase (BChE) in plasma. AChE was also evaluated in total brain. The activity of AChE in blood and brain, and the activity of BChE in plasma significantly reduced in the infected cats. Therefore, the infection by T. evansi influenced cholinesterases of felines indicating changes in the responses of the cholinergic system.

Diminazene aceturate in the control of Trypanosoma evansi infection in cats.

The aim of this study was to investigate the efficacy of diminazene aceturate in the control of the infection by Trypanosoma evansi in cats. Fourteen animals were infected with 10(8) trypomastigote forms each and six were used as negative control (group A). Seven of the infected cats were used as positive control (group B) and seven were treated with diminazene aceturate (3.5 mg kg(-1)) for 5 consecutive days (group C). Biochemical and hematological parameters were evaluated during the experiment. Blood with anticoagulant was collected at day 49 post-inoculation and preserved in ethanol for DNA extraction. Samples were analyzed using PCR T. evansi-specific to assess the effectiveness of treatment. The treatment with diminazene aceturate had an efficacy of 85.7%. Alanine aminotransferase, gamma-glutamyltransferase, urea, and creatinine values remained within the normal physiological range in the treated cats. Hemogram was normalized in all the cured animals. Therefore, the therapy used is effective in controlling T. evansi in cats.