Search Results (31)

Background/Objectives: Acanthamoeba keratitis (AK) is a rare but sight-threatening corneal infection, often associated with contact lens wear and resistant to conventional therapies. Preventive strategies capable of reducing Acanthamoeba adhesion to corneal epithelium may represent an important tool for infection control. This study aimed to evaluate the amebicidal and preventive activity of CORNEIAL MED eye drops against Acanthamoeba castellanii adhesion and early adhesion layer on human corneal epithelium (HCE). Methods: Reconstructed HCE models were exposed to A. castellanii under four experimental conditions: negative control (HCE only), positive control (HCE + A. castellanii), co-incubation with CORNEIAL MED and A. castellanii (Study 1), and treatment with CORNEIAL MED after initial A. castellanii adhesion (Study 2). Adherent amoebae were quantified using EDTA detachment and Neubauer chamber counting. The early adhesion layer was characterized by scanning electron microscopy (SEM). Statistical analysis considered p < 0.05 as significant. Results: In Study 1, simultaneous application of CORNEIAL MED with A. castellanii reduced amoeba adhesion by 33.0 ± 11% compared with controls (p = 0.0529). In Study 2, when the product was applied 3 h after amoeba inoculation, adhesion was significantly reduced by 51.9 ± 6.5% (p < 0.05). SEM confirmed a decrease in amoebic colonization and biofilm density in treated samples. Conclusions: CORNEIAL MED demonstrated a measurable inhibitory effect on A. castellanii adhesion to HCE, particularly when applied after initial pathogen contact. These findings suggest a potential preventive role of CORNEIAL MED in reducing AK risk, although further in vivo studies are warranted. Full article

The increasing global incidence of infections caused by free-living amoebae (FLA) and the lack of effective, safe, and approved treatments highlight the urgent need for novel amoebicidal compounds with pharmacological potential. Despite a growing body of literature on the anti-FLA properties of various compounds, comprehensive reviews summarizing this progress remain scarce. This study aimed to identify the most promising compounds tested in vitro and/or in vivo for anti-FLA activity. A systematic review was conducted, analyzing 108 studies published between 1986 and 2024, selected from an initial pool of 23,653 database results. A total of 537 compounds were evaluated for their in vitro anti-FLA activity. Compounds exhibiting ≥50% reduction in amoeba viability relative to untreated controls were classified as promising if they showed low toxicity in mammalian cell models, particularly when active at concentrations ≤ 10 µM, consistent with predicted favorable pharmacokinetic and pharmacodynamic profiles. The most promising compounds for drug and disinfectant development include ten trophocidal agents against B. mandrillaris, thirty-two trophocidal and four cysticidal agents against N. fowleri, and sixty-two trophocidal and nineteen cysticidal agents against Acanthamoeba spp. Compounds active at low concentrations (≤10 µM or <0.014 mg/mL) prioritized for in vivo drug development studies include: against Balamuthia mandrillaris, trophocidal 515, 531, 533; against Naegleria fowleri, trophocidal 421, 416, 518, 46, 254, 522, 111–120 and cysticidal 16; and against Acanthamoeba spp., trophocidal 498, 499, 500, 535, 107, 347, 348, and 340. Future studies should evaluate their efficacy, safety, pharmacokinetics, and pharmacodynamics toward developing effective drugs, antiseptics, and disinfectants. Full article

Current therapies for Primary Amoebic Meningoencephalitis (PAM) present several limitations; consequently, there is an urgent need to develop new therapeutic agents. In this regard, we undertook bioassay-guided isolation of Mentha rotundifolia leaves which allowed the identification of ursolic acid (1) as the main bioactive metabolite against two ATCC strains of Naegleria fowleri (ATCC^® 30808^TM and ATCC^® 30215^TM). Moreover, ten ursolic acid derivatives (2–11) were synthesized through esterification and nucleophilic substitution to obtain halo or amino ester derivatives. Among these derivatives, compound 7 exhibited the highest activity against the N. fowleri ATCC^® 30808^TM strain with an IC₅₀ value of 28.66 µM, whereas compound 10 showed the top activity against the N. fowleri ATCC^® 30215^TM strain with an IC₅₀ of 7.61 µM, surpassing the efficacy of the reference drug, miltefosine. Both compounds, 7 and 10, showed a good selectivity index and hence low toxicity in vitro. Structure–activity relationship studies revealed that the type of acylating agent played a crucial role in the activity. Furthermore, both compounds induced autophagy and apoptosis-like processes in both treated N. fowleri strains. These results highlight the potential of ursolic acid-related triterpenoids as drug scaffolds and identify M. rotundifolia as a promising natural source of amoebicidal agents against PAM. Full article

Acanthamoeba keratitis (AK) is a sight-threatening and difficult-to-treat ocular infection. The significant side effects of current AK treatments highlight the urgent need to develop a safe and effective AK medication. In this study, the amoebicidal activity of Iris setosa Pall. ex Link extract (ISE) against Acanthamoeba was examined and its specific amoebicidal mechanism was explored. ISE induced significant morphological changes in Acanthamoeba trophozoites and exhibited amoebicidal activity against A. castellanii and A. polyphaga. ISE was further fractionated into five subfractions by sequential extraction with n-hexane, chloroform, ethyl acetate, n-butanol, and water, and their amoebicidal activities and underlying amoebicidal mechanisms were investigated. The n-butanol subfraction of ISE (ISE-BuOH) displayed selective amoebicidal activity against the Acanthamoeba species with minimal cytotoxicity in human corneal cells (HCE-2). ISE-BuOH triggered apoptosis-like programmed cell death (PCD) in amoebae, characterized by DNA fragmentation, increased ROS production, and caspase-3 activity elevation. ISE-BuOH also demonstrated a partial cysticidal effect against the amoeba species. ISE-BuOH could be a promising candidate in the development of therapeutic drugs for AK. Full article

Acanthamoeba spp. can cause a sight threatening disease. At present, the current treatments used to treat Acanthamoeba spp. Infections, such as biguanide-based antimicrobials, remain inefficacious, with the appearance of resistant forms and high cytotoxicity to host cells. In this study, an initial screening was conducted against Acanthamoeba castellanii Neff and murine macrophages J774A.1 using alamarBlue™. Among the 160 compounds included in the cited box, 90% exhibited an inhibition of the parasite above 80%, while only 18.75% of the compounds inhibited the parasite with a lethality towards murine macrophage lower than 20%. Based on the amoebicidal activity, the cytotoxicity assay, and availability, Terconazole was chosen for the elucidation of the action mode in two clinical strains, Acanthamoeba culbertsoni and Acanthamoeba castellanii L10. A fluorescence image-based system and proteomic techniques were used to investigate the effect of the present azole on the cytoskeleton network and various programmed cell death features, including chromatin condensation and mitochondria dysfunction. Taking all the results together, we can suggest that Terconazole can induce programmed cell death (PCD) via the inhibition of sterol biosynthesis inhibition. Full article

Human amoebiasis still represents a major health problem worldwide. Metronidazole has been used as the most common drug to treat the disease; however, it is also known that the drug causes undesirable side effects. This has led to the search for new pharmacological alternatives which include phytochemical compounds with antiamoebic effects. We analyzed the amoebicidal activity of stevioside (STV), a diterpene glycoside present in Stevia rebaudiana, on trophozoites of E. histolytica. Different concentrations of STV were tested, and an inhibitory concentration of 50% of cell viability (IC₅₀) was determined with an exposition of 9.53 mM for 24 h. Trophozoites exposed to STV showed morphological changes evidenced by the decrease in the basic structures related to the movement and adherence to the substrate, as well as ultrastructural features characterized by a loss of regularity on the cell membrane, an increase in cytoplasmic granularity, and an increase in apparent autophagic vacuoles. Also, the decrease in cysteine protease expression and the proteolytic activity of trophozoites to degrade the cell monolayer were analyzed. A histological analysis of hamster livers inoculated with trophozoites and treated with STV showed changes related to the granulomatous reaction of the liver parenchymal tissue. Our results constitute the first report related to the possible use of STV as a therapeutic alternative in amoebiasis. Full article

Caffeic acid (CA) is one of the most abundant natural compounds present in plants and has a broad spectrum of beneficial pharmacological activities. However, in some cases, synthetic derivation of original molecules can expand their scope. This study focuses on the synthesis of caffeic acid phosphanium derivatives with the ambition of increasing their biological activities. Four caffeic acid phosphanium salts (CAPs) were synthesized and tested for their cytotoxic, antibacterial, antifungal, and amoebicidal activity in vitro, with the aim of identifying the best area for their medicinal use. CAPs exhibited significantly stronger cytotoxic activity against tested cell lines (HeLa, HCT116, MDA-MB-231 MCF-7, A2058, PANC-1, Jurkat) in comparison to caffeic acid. Focusing on Jurkat cells (human leukemic T cell lymphoma), the IC₅₀ value of CAPs ranged from 0.9 to 8.5 μM while IC₅₀ of CA was >300 μM. Antimicrobial testing also confirmed significantly higher activity of CAPs against selected microbes in comparison to CA, especially for Gram-positive bacteria (MIC 13–57 μM) and the yeast Candida albicans (MIC 13–57 μM). The anti-Acanthamoeba activity was studied against two pathogenic Acanthamoeba strains. In the case of A. lugdunensis, all CAPs revealed a stronger inhibitory effect (EC₅₀ 74–3125 μM) than CA (>10⁵ µM), while in A. quina strain, the higher inhibition was observed for three derivatives (EC₅₀ 44–291 μM). The newly synthesized quaternary phosphanium salts of caffeic acid exhibited selective antitumor action and appeared to be promising antimicrobial agents for topical application, as well as potential molecules for further research. Full article

Naegleria fowleri is a ubiquitous free-living amoeba that causes primary amoebic meningoencephalitis. As a part of the innate immune response at the mucosal level, the proteins lactoferrin (Lf) and lysozyme (Lz) are secreted and eliminate various microorganisms. We demonstrate that N. fowleri survives the individual and combined effects of bovine milk Lf (bLf) and chicken egg Lz (cLz). Moreover, amoebic proliferation was not altered, even at 24 h of co-incubation with each protein. Trophozoites’ ultrastructure was evaluated using transmission electron microscopy, and these proteins did not significantly alter their organelles and cytoplasmic membranes. Protease analysis using gelatin-zymograms showed that secreted proteases of N. fowleri were differentially modulated by bLf and cLz at 3, 6, 12, and 24 h. The bLf and cLz combination resulted in the inhibition of N. fowleri-secreted proteases. Additionally, the use of protease inhibitors on bLf-zymograms demonstrated that secreted cysteine proteases participate in the degradation of bLf. Nevertheless, the co-incubation of trophozoites with bLf and/or cLz reduced the cytopathic effect on the MDCK cell line. Our study suggests that bLf and cLz, alone or together, inhibited secreted proteases and reduced the cytopathic effect produced by N. fowleri; however, they do not affect the viability and proliferation of the trophozoites. Full article

Acanthamoeba is a ubiquitous genus of amoebae that can act as opportunistic parasites in both humans and animals, causing a variety of ocular, nervous and dermal pathologies. Despite advances in Acanthamoeba therapy, the management of patients with Acanthamoeba infections remains a challenge for health services. Therefore, there is a need to search for new active substances against Acanthamoebae. In the present study, we evaluated the amoebicidal activity of nitroxoline against the trophozoite and cyst stages of six different strains of Acanthamoeba. The strain A. griffini showed the lowest IC₅₀ value in the trophozoite stage (0.69 ± 0.01 µM), while the strain A. castellanii L-10 showed the lowest IC₅₀ value in the cyst stage (0.11 ± 0.03 µM). In addition, nitroxoline induced in treated trophozoites of A. culbertsoni features compatibles with apoptosis and autophagy pathways, including chromatin condensation, mitochondrial malfunction, oxidative stress, changes in cell permeability and the formation of autophagic vacuoles. Furthermore, proteomic analysis of the effect of nitroxoline on trophozoites revealed that this antibiotic induced the overexpression and the downregulation of proteins involved in the apoptotic process and in metabolic and biosynthesis pathways. Full article

Amoebiasis is the second leading cause of death worldwide associated with parasitic disease and is becoming a critical health problem in low-income countries, urging new treatment alternatives. One of the most promising strategies is enhancing the redox imbalance within these susceptible parasites related to their limited antioxidant defense system. Metal-based drugs represent a perfect option due to their extraordinary capacity to stabilize different oxidation states and adopt diverse geometries, allowing their interaction with several molecular targets. This work describes the amoebicidal activity of five 2-(Z-2,3-diferrocenylvinyl)-4X-4,5-dihydrooxazole derivatives (X = H (3a), Me (3b), iPr (3c), Ph (3d), and benzyl (3e)) on Entamoeba histolytica trophozoites and the physicochemical, experimental, and theoretical properties that can be used to describe the antiproliferative activity. The growth inhibition capacity of these organometallic compounds is strongly related to a fine balance between the compounds’ redox potential and hydrophilic character. The antiproliferative activity of diferrocenyl derivatives studied herein could be described either with the redox potential, the energy of electronic transitions, logP, or the calculated HOMO–LUMO values. Compound 3d presents the highest antiproliferative activity of the series with an IC₅₀ of 23 µM. However, the results of this work provide a pipeline to improve the amoebicidal activity of these compounds through the directed modification of their electronic environment. Full article

(1) Background: The aim of the study was to compare the potency of Plantago media L. (Plantaginaceae) extracts on Acanthamoeba sp. trophozoites, which are opportunistic protozoan parasites leading to several dangerous diseases; (2) Methods: The chromatographically (TLC, HPLC-DAD) characterized water fractions of the extracts from biomass from in vitro cultures (shoots and roots), leaves, and inflorescences from field cultivation were used for the study of the acanthamoebic activity in a Thoma haemocytometer chamber; (3) Results: The anti-amoebic effect at the lowest concentration (1.0 mg/mL) was demonstrated only by the extract of the leaves from the cultivation (50.50% inhibition). The remaining samples inhibited the growth of parasites from a concentration of 5.0 mg/mL in the range of 41.36% inflorescences to 63.89% shoots in vitro. Quantitative determinations of phenolic compounds in the tested extracts indicate a tendency to increase the potency of the anti-amoebic effect with the content of a phenylethanoid glycoside—acteoside. The maximum content of this compound was determined in leaves from field cultivation (6.64%) and the minimum in inflorescences (0.65%). This is confirmed by the range of the lowest IC₅₀ values (the strongest biological activity) for the tested samples, 0.95–1.80 mg/mL for leaves from cultivation, and the high values, 9.70–5.30 mg/mL for inflorescences and in-vitro-derived roots. The strength of the biological activity of the extracts correlated with the content of acteoside, which constituted 84–93% of the sum of phenolic compounds determined; (4) Conclusions: The performed investigations proved the anti-acanthamoebic efficacy of Plantago media organs, including those obtainable by biotechnological methods, and indicated phenylethanoid glycosides, their main phenolic constituents, to be responsible for the activity. To our knowledge, this is the first report on the amoebicidal activity of Plantago media extracts from biomass produced by biotechnological methods and organs of an intact plant. Full article

Acanthamoeba keratitis (AK) is a rare cornea disease caused by species of the Acanthamoeba genus. The antifungal voriconazole blocks the ergosterol synthesis in the protozoan membrane and is active against the cysts and trophozoites of Acanthamoeba spp. Due to the low stability of voriconazole, its options for eye drops are scarce. This study aimed to investigate the stability of the biological activity of voriconazole against two strains of Acanthamoeba castellanii and one clinical isolate from a patient with AK. To evaluate the stability of the biological activity of voriconazole, strains of A. castellanii (ATCC 50492) were exposed to different periods and voriconazole concentrations stored at 4 °C for 7, 15, and 30 days. The cytotoxicity assays were performed using SIRC (ATCC CCL-60™) cell line. The results indicated the amoebicidal effect of voriconazole against Acanthamoeba spp. within 24 h and 48 h of exposure, and the voriconazole solution was stable and retained antiamoebic activity when stored at 4 °C for up to 30 days. In the cytotoxicity test, the result demonstrated low cytotoxicity of the drug to the corneal rabbit cell line. However, there is a need to carry out further synergistic effects with other antiamoebic drugs and then in vivo experiments in the AK animal model. Full article

Acanthamoeba keratitis (AK) is an infectious ocular disease which is difficult to diagnose correctly and cure. Development of an effective and safe therapeutic drug for AK is needed. Our preliminary screening of more than 200 extracts from wild plants collected in Korea suggested the potential amoebicidal activity of Phragmites australis (Cav.) Trin. ex Steud. extract (PAE) against Acanthamoeba species. Here, we aimed to analyze the amoebicidal activity of PAE on Acanthamoeba and its underlying amoebicidal mechanism. PAE induced amoebicidal activity against both A. castellanii and A. polyphaga trophozoites, while it showed low cytotoxicity in human corneal epithelial cells (HCE-2) and human retinal pigment epithelial cells (ARPE-19). Transmission electron microscopy analysis showed subcellular morphological changes, such as increased granules, abnormal mitochondria, and atypical cyst wall formation, in the PAE-treated A. castellanii. Fluorometric apoptosis assay and TUNEL assay revealed apoptosis-like programmed cell death (PCD) in the PAE-treated A. castellanii. The PAE treatment increased reactive oxygen species production and reduced mitochondrial membrane potential in the amoeba. The enhanced expression of autophagy-associated genes was also detected. These results suggested that PAE exerted a promising amoebicidal effect on A. castellanii trophozoites via the PCD pathway. PAE could be a potential candidate for developing a therapeutic drug for AK. Full article

Acanthamoeba is a free-living protozoan known to cause keratitis most commonly, especially among contact lens wearers. Treatment of Acanthamoeba keratitis is challenging as Acanthamoeba can encyst from the active form, a trophozoite, into a hibernating cyst that is refractory to antibiotics and difficult to kill; therefore, there is a need for more effective anti-amoebic strategies. In this study, we have evaluated the anti-amoebic activity of the antimicrobial peptide mimic RK-758 against Acanthamoeba castellanii. RK-758 peptidomimetic was subjected to biological assays to investigate its amoebicidal, amoebistatic, anti-encystation, and anti-excystation effects on A. castellanii. The anti-amoebic activity of the peptide mimic RK-758 was compared with chlorhexidine against the Acanthamoeba castellanii ATCC30868 and Acanthamoeba castellanii 044 (a clinical strain) with the concentrations of both ranging from 125 µM down to 7.81 µM. All experiments were performed in duplicate with three independent replicates. The data were represented as mean ± SE and analysed using a two-sample t-test and two-tailed distributions. A p < 0.05 was considered statistically significant. The peptidomimetic RK-758 had anti-Acanthamoeba activity against both trophozoites and cysts in a dose-dependent manner. The RK-758 had amoebicidal and growth inhibitory activities of ≥50% at a concentration between 125 µM and 15.6 µM against the trophozoites of both Acanthamoeba strains. Inhibitory effects on the cyst formation and trophozoite re-emergence from cysts were noted at similar concentrations. Chlorhexidine had 50% activity at 7.81 µM and above against the trophozoites and cysts of both strains. In the haemolysis assay, the RK-758 lysed horse RBCs at concentrations greater than 50 µM whereas lysis occurred at concentrations greater than 125 µM for the chlorhexidine. The peptidomimetic RK-758, therefore, has activity against both the trophozoite and cyst forms of Acanthamoeba and has the potential to be further developed as an anti-microbial agent against Acanthamoeba. RK-758 may also have use as an anti-amoebic disinfectant in contact lens solutions. Full article

Acanthamoeba castellanii is a ubiquitous free-living amoeba capable of instigating keratitis and granulomatous amoebic encephalitis in humans. Treatment remains limited and inconsistent. Accordingly, there is a pressing need for novel compounds. Nanotechnology has been gaining attention for enhancing drug delivery and reducing toxicity. Previous work has shown that various antibiotic classes displayed antiamoebic activity. Herein, we employed two antibiotics: ampicillin and ceftriaxone, conjugated with the nanocarrier zinc oxide and β-cyclodextrin, and tested them against A. castellanii via amoebicidal, amoebistatic, encystment, excystment, cytopathogenicity, and cytotoxicity assays at a concentration of 100 μg/mL. Notably, zinc oxide β-cyclodextrin ceftriaxone significantly inhibited A. castellanii growth and cytopathogenicity. Additionally, both zinc oxide β-cyclodextrin ceftriaxone and ceftriaxone markedly inhibited A. castellanii encystment. Furthermore, all the tested compounds displayed negligible cytotoxicity. However, minimal anti-excystment or amoebicidal effects were observed for the compounds. Accordingly, this novel nanoconjugation should be employed in further studies in hope of discovering novel anti-Acanthamoeba compounds. Full article