Pathogenic and opportunistic free-living amoebae: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea

Toll-like receptors and inflammatory cytokines in the skin of Acanthamoeba spp. infected immunocompetent and immunosuppressed mice

Acanthamoeba spp. can cause opportunistic infections, such as cutaneous acanthamoebiasis (CA). Little is known about the role of TLRs and cytokines in the host skin during Acanthamoeba spp. infections. The study aimed to examine the gene and protein expression of TLR3, TLR7, IFN-γ, and IL-23 in the skin of mice experimentally infected with a clinical strain of Acanthamoeba spp. male BALB/c mice were assigned to four groups: group I (control group I) - with normal immunity (C, n = 5); group II (control group II) - with reduced immunity induced by methylprednisolone sodium succinate (MPS; CS, n = 5); group III - amoeba-infected hosts with normal immunity (A, n = 12); and group IV- amoeba-infected hosts with reduced immunity induced by MPS (AS, n = 12). The skin sections (2 cm × 2 cm) were collected from the animals at 8, 16, and 24 days post-infection (dpi). TLR3, TLR7, IFN-γ, and IL-23 gene and protein expressions were analyzed by quantitative real-time PCR and immunohistochemical staining. In the immunocompetent hosts, we noted higher expressions of TLR3 and IL-23 at all-time points, except 8th dpi when IL-23 gene expression was downregulated compared to the control group. The mRNA expressions of TLR7 and IFN-γ were higher at 16 and 24 dpi in the skin of immunocompetent Acanthamoeba spp.-infected hosts than in the uninfected mice. In the course of acanthamoebiasis in the mice with reduced immunity, we found significant upregulation of TLR3, IL-23, and TLR7 gene expressions only at the beginning of infection compared to the control group. A similar relationship was observed for IFN-γ at 8 and 16 dpi. The pathophysiology of Acanthamoeba infection in the skin is complex. The data presented in this paper add new insight, but they are not sufficient to explain the role of the studied receptors and cytokines. The clinical picture and mechanisms of host response appear to be influenced by the route of infection, immunological status and microorganisms carried within the parasites. CA remains a multifactorial phenomenon.

Potentially pathogenic free-living amoebae at very high altitude: Detection by multiplex qPCR in the Northern Altiplano fascioliasis hyperendemic area in Bolivia

Free-living amoebae (FLA), which are frequently found in the environment, include opportunistic pathogenic genera/species such as Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri and Vermamoeba vermiformis. These pathogenic FLA are causative agents of amoebic encephalitis and keratitis in the case of Acanthamoeba genus and V. vermiformis. In addition, amoebic infections are often related to contamination of domestic and recreational water sources. This study aimed to identify potentially pathogenic FLA in the hyperendemic area of human fascioliasis in a very-high-altitude area (3800-4100 m a.s.l.) of Bolivia and examine whether an association between both pathogens could be established from the environmental point of view. A total of 55 samples (28 soil and 27 water samples) were collected from various locations in the Northern Altiplano of Bolivia. Samples were processed by multiplex qPCR to detect the four pathogenic FLA genera/species. All samples were positive for the presence of V. vermiformis, followed by Acanthamoeba spp. which was positive in 18 soil and 10 water samples. In contrast, B. mandrillaris was only detected in soil sources, whereas N. fowleri was not detected in any of the samples. The coexistence and diverse distribution of multiple FLA species in many locations at such a high altitude is worth mentioning and indicates a potential risk of coinfections. These findings suggest that FLA surveillance is a crucial factor to be considered when implementing preventive measures and improving public health in fascioliasis hyperendemic areas.

Virulence of Naegleria fowleri isolates varies significantly in the mouse model of primary amoebic meningoencephalitis

Naegleria fowleri is a small free-living amoeba that causes an acute, fatal disease called primary amoebic meningoencephalitis (PAM). One persisting question is why few people succumb to disease when so many are potentially exposed. We tested the hypothesis that N. fowleri isolates vary in virulence and in the minimum infectious dose required to induce disease by using a mouse model of PAM and intranasally inoculating dilutions of five clinical isolates of N. fowleri. Results showed significant differences in onset of severe disease and mortality rates between isolates. Remarkably, for isolate V596, 100 amoebae produced 100% mortality within 5 days. In contrast, higher numbers of amoebae were required for other isolates and mice survived for >2 weeks. Concurrently, we developed an in vitro virulence assay by comparing feeding rates between amoebae isolates seeded onto Vero cells. We observed a positive correlation between cytopathic effects in vitro and virulence in vivo.

Acute meningoencephalitis with subdural empyema associated with Acanthamoeba in an immunocompetent individual

Acanthamoeba-induced meningoencephalitis is a rare and frequently fatal condition. We describe a case of acute Acanthamoeba meningoencephalitis complicated by subdural empyema in a previously healthy 50-year-old man who presented with high-grade fever, neck stiffness and left-sided hemiparesis. Neuroimaging revealed a subdural collection in the right fronto-temporo-parietal region, while cerebrospinal fluid analysis demonstrated neutrophilic pleocytosis with trophozoites morphologically consistent with Acanthamoeba species. The patient underwent burr-hole evacuation of the subdural collection and was managed with antimicrobial therapy and supportive care. The patient achieved complete recovery and was discharged after 2 weeks. This case underscores the importance of considering Acanthamoeba as a potential etiological agent in meningoencephalitis, even among immunocompetent individuals and highlights the critical role of early diagnosis and timely intervention in improving clinical outcomes.

Moving Beyond the Silos of Opportunistic Pathogen and Disinfection Byproduct Research to Improve Drinking Water System Management

Drinking water opportunistic pathogens (OPs) and disinfection byproducts (DBPs) both pose risks to public health, and their variable occurrence from source to tap complicates efforts to control them simultaneously. Management of OPs and DBPs is further hindered by the historical division between microbial and chemical research. This review brings together the current knowledge regarding OPs and DBPs, identifies factors that influence the occurrence of both, and highlights areas where research is needed to better understand their health risks. First, we examine the current understanding of how OPs and DBPs are jointly influenced by physicochemical parameters, source water characteristics, treatment processes including disinfection, and distribution system properties. Temperature, for example, can affect OP and DBP occurrence, where higher temperatures can promote the growth of some OPs, such as Legionella pneumophila, but temperature's effect on DBPs is species-dependent. Methods for quantifying the risks associated with OPs (quantitative microbial risk assessment) and DBPs (chemical risk assessment) are compared, finding that the numerous assumptions and data gaps associated with each method limit comparability across contaminant types. We highlight the urgent need to fill existing data gaps and develop a more unified risk framework so as to move toward holistic assessment of microbial and chemical risks. This review provides suggestions for future research, highlighting ways that researchers might utilize established practices in OP or DBP studies to further our understanding of the other. For example, analysis of source water organic matter composition, which has advanced our understanding of DBP formation, could be utilized to elucidate how source water characteristics influence OPs. This review bridges the gap between the OP and DBP disciplines, arguing that collaboration between the two is needed to address the pressing challenges facing water systems today.

Assessment of the Presence of Free-Living Amoebae in Soil Samples from the Northwest Region of Spain Using Culture and Molecular Assays

Free-living amoebae (FLA) such as Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, Sappinia spp., Vahlkampfia spp., and Vermamoeba vermiformis are naturally widespread in the environment, causing rare but fatal and debilitating infections in humans. In the present study, a total of 87 soil samples were collected from four provinces in the autonomous community of Castilla y León, Spain. These samples were collected in three different seasons during 2022-2023 (t1-t3) and were analysed by culture and molecular techniques (conventional PCR/sanger sequencing and qPCR). The obtained data revealed that the genus Acanthamoeba and the species Vermamoeba vermiformis were the most prevalent FLA. Furthermore, other genera/species of FLA were identified in the tested soil sources, suggesting a rich microbial biodiversity in Castilla y León soils. In addition, this study provides an important basis for future research on the ecology of these organisms and their potential impact on public health and the environment.

Advances in the study of extracellular vesicles of Naegleria fowleri and their role in contact-independent pathogenic mechanisms

BACKGROUND

Extracellular vesicles (EVs) are spherical membrane particles released by prokaryotic and eukaryotic cells. EVs produced by pathogenic organisms are known to play a role in host-pathogen interactions; however, despite some reports on Naegleria fowleri EVs, their potential role in inducing cytopathic effects remains poorly understood. In this study, we evaluated the role of N. fowleri EVs in contact-independent pathogenic mechanisms.

METHODS

Extracellular vesicles were characterized via transmission electron microscopy, nanoparticle tracking analysis, SDS-PAGE, mass spectrometry, Western blotting, and zymography. EVs internalization by trophozoites and MDCK epithelial cells was also determined. Finally, mammalian cells were coincubated with EVs to evaluate haemolytic activity, epithelial paracellular ionic permeability alterations, and necrosis.

RESULTS

Naegleria fowleri extracellular vesicles, ranging from 82.5 to 576.5 nm in size, were isolated, with a mean of 216.8 nm and a mode of 165.3 nm. Proteomic analysis identified 1006 proteins in the EVs, including leishmanolysin, a protein associated with pathogenic mechanisms such as adhesion and enzymatic processes. The proteolytic activity of EVs was found to be primarily due to serine protease. Furthermore, EVs were internalized by both trophozoites and MDCK cells. Additionally, EVs exhibited haemolytic activity in erythrocytes as well as increased ionic permeability and necrosis in MDCK cells 24 h postinteraction.

CONCLUSIONS

Naegleria fowleri EVs exhibit proteolytic and haemolytic activity and are internalized by trophozoites and MDCK epithelial cell monolayers, increasing the ionic permeability of the monolayer and inducing necrosis. Furthermore, these vesicles contain molecules associated with pathogenic processes such as leishmanolysin. Our results suggest that EVs facilitate paracellular invasion, migration, and damage caused by trophozoites and play a significant role in pathogenic processes as part of a contact-independent mechanism, which, in conjunction with a contact-dependent mechanism, enhances our understanding of the pathogenicity exhibited by this amphizoic amoeba during its invasion of target tissues.

Epidemiology, molecular characterization, and risk factors of Acanthamoeba spp., Blastocystis spp., and Cyclospora spp. infections in snakes in China

Snakes are widely farmed in China for medicinal purposes and as pets worldwide. Acanthamoeba spp., Blastocystis spp., and Cyclospora spp. are significant zoonotic pathogens frequently discovered in various animals, causing diseases with global public health implications. However, their prevalence and zoonotic potential in snakes remain poorly understood. In this study, 812 snake faecal samples were collected across 28 China provinces. The partial small subunit (SSU) rRNA gene was amplified using polymerase chain reaction (PCR) to assess evolutionary relationships and genetic characterization. Detection rates for Acanthamoeba spp., Blastocystis spp., and Cyclospora spp. were 6.40 %, 3.33 %, and 2.71 %, respectively. Sequencing and phylogenetic analysis revealed that Cyclospora isolates were closely related to those found in humans and cattle. Subtyping for Blastocystis species identified two zoonotic subtypes (ST4, ST6) and four host-specific subtypes (ST10, ST15, ST21, ST42). Multiple Acanthamoeba genotypes were detected, including T4, T11, and T13. Furthermore, species, age, and living conditions are key risk factors. This study provides valuable insights into these infections in snakes and underscores the need for proper hygiene and One Health measures to reduce zoonotic transmission and environmental contamination.

Prevalence of free-living amoebae in five rivers associated with high human activity in Tehran province, Iran

Free-living amoebae (FLA) are ubiquitous protozoa capable of enduring harsh environmental conditions. These microorganisms are commonly found in water, soil, and air and can be transmitted to humans in areas with high human activity. This study aimed to investigate the prevalence of FLA and their associated genotypes/species in five rivers in Tehran province, Iran. A total of 60 water samples were collected from the Jajrud, Kan, Farhzad, Darakeh, and Shadchay rivers. Samples were subjected to filtration and cultivation onto non-nutrient agar. The genera/species of FLA were characterized based on the amplification and sequencing of the specific genetic fragments. Microscopic analysis suggested the presence of trophozoites and cysts of FLA in 18/60 (30%) of samples, of which Acanthamoeba spp., Vermamoeba sp., and Vahlkampfiidae were identified. Sequence analysis showed the presence of the genotypes T11, T4, T3, and T5 in five, five, four, and one isolates, respectively. The molecular analysis of the T4 genotype showed gene flow between the current isolates with previously described sequences. The findings suggest a clear association between environmental and clinical isolates of Acanthamoeba spp. Therefore, scheduled monitoring of environmental waters, particularly in regions with high human activities, is highly recommended.

Recent in vitro advances in the ocular antimicrobial agents against Acanthamoeba

This review examines the advancements in antimicrobial drug discovery with in vitro assays for Acanthamoeba, highlighting the efficacy of current topical antimicrobial agents. In recent decades, the treatment and diagnosis of Acanthamoeba keratitis (AK) have presented clinical challenges. Clinicians often rely on clinical judgment, risk factors, and patient travel history to guide initial treatment decisions. The clinical presentation of AK frequently coincides with bacterial and fungal keratitis, leading to delays in diagnostic confirmation. This review compiles a list of commonly used antimicrobial agents that may be useful in controlling and preventing Acanthamoeba and other microbial infections during the diagnostic waiting period. Due to their unique life cycle, consisting of both trophozoite and cyst stages, amoebae exhibit resistance to various clinical drugs. Current research efforts are focused on identifying alternative and effective treatment options. Despite the ongoing characterization of various cytocidal agents from natural and synthetic sources, chlorhexidine gluconate (CHG) and polyhexamethylene biguanide (PHMB) have emerged as the most effective therapies for AK. Drawing from previous studies, we catalog several commonly used antimicrobial agents that may enhance the efficacy of PHMB and CHG while also preventing other microbial infections. These alternative agents present promising options for treating AK cases. This review evaluates progress in anti-amoebic drug discovery, focusing on antibiotics and cataloging their activity at different stages of Acanthamoeba.

Advancing the understanding of Naegleria fowleri: Global epidemiology, phylogenetic analysis, and strategies to combat a deadly pathogen

Naegleria fowleri is a rare but deadly pathogen that has emerged as an important global public health concern. The pathogen induces primary amoebic meningoencephalitis (PAM), a rapidly progressive and almost always fatal life-threatening brain infection. The devastating impact of N. fowleri and the high mortality rate underscores a deeper understanding and the development of innovative strategies to tackle this issue. Despite various studies that have been conducted on N. fowleri, a comprehensive review that integrates recent findings and addresses critical gaps in understanding remains lacking. This review provides a detailed overview of N. fowleri epidemiology, transmission dynamics, phylogenetic diversity, state-of-the-art diagnostic techniques, therapeutic approaches, and preventive measures. We identified 488 PAM cases globally, reported since 1962, with the highest numbers in the US, Pakistan, and Australia. A phylogenetic analysis of 41 N. fowleri ITS-1, 5.8S, ITS-2 region-based sequences showed genotypic diversity, with genotypes II and III being the most prevalent in Asia, North America, and Europe. Effective approaches to preventing N. fowleri transmission include applying free chlorine to water in storage tanks, taking precautions while swimming, and performing ablution with sterilized water (e.g., boiled or distilled) while avoiding deep inhalation of water, especially in regions with high water contamination. This review highlights the global impact of N. fowleri, future surveillance strategies, prompt diagnosis, potential therapeutic options, and vaccine development to prevent PAM outbreaks. It highlights the importance of joint government and public health efforts to combat this deadly pathogen.

Imidazolium salt as potent Amoebicide for rapid inactivation of Acanthamoeba spp. trophozoites and cysts

Acanthamoeba spp. are amphizoic protozoa capable of causing several severe diseases in humans and other animals, including granulomatous amoebic encephalitis and Acanthamoeba keratitis (AK). The high resistance of Acanthamoeba genus, especially in its cystic form, to most conventional disinfectants poses a challenge for its management through aseptic practices based on chemical disinfectants. The imidazolium salt (IS) (C16MImCl) demonstrated significant acanthamoebicidal potency against both trophozoites and cysts. However, its biocidal efficacy over a short exposure time, which will shed light on its potential use as a disinfectant, still needs to be studied. Therefore, the acanthamoebicidal effect of IS against trophozoites and cysts of Acanthamoeba polyphaga and Acanthamoeba spp. exposed for 5 and 20 min to concentrations of 250, 125, 62.5, 31.25, 15.62, and 7.81 μg/mL was evaluated in the present study. Exposure of trophozoites of both strains to IS for 20 min significantly reduced trophozoite viability at concentrations ≥62.5 μg/mL. All trophozoites of both strains were inactived 20 min after cessation of IS exposure at concentrations of ≥125 μg/mL for 5 min or ≥15 μg/mL for 20 min. Cyst viability of all strains was significantly reduced after 20 min of exposure to IS at 62.5 and 125 μg/mL, based on the viability exclusion assay with trypan blue dye. However, all cysts exposed to IS at ≥ 125 μg/mL for 20 or 5 min were unable to excyst when incubated for 10 days on non-nutrient agar with Escherichia coli. The acanthamoebicidal efficacy of IS, upon short exposure to concentrations below the cytotoxic value for human keratinocyte cells (IC50 = 171.50 μg/mL), combined with its previously reported bactericidal and fungicidal effects, suggests that IS has the potential to be used in the formulation of multipurpose disinfectants.

Nitroxoline evidence amoebicidal activity against Acanthamoeba castellanii through DNA damage and the stress response pathways

Acanthamoeba castellanii is a widespread unicellular eukaryote found in diverse environments, including tap water, soil, and swimming pools. It is responsible for severe infections, such as Acanthamoeba keratitis and granulomatous amebic encephalitis, particularly in individuals with immunocompromisation. The ability of protozoans to form dormant and persistent cysts complicates treatment, as current therapies are ineffective against cyst stages and suffer from poor specificity and side effects. Nitroxoline, a quinoline derivative with well-established antibacterial, antifungal, and antiviral properties, is a promising therapeutic candidate. This study aimed to elucidate cellular signalling events that counteract the effects of nitroxoline. In this study, nitroxoline significantly reduced the viability of A. castellanii trophozoites in a dose- and time-dependent manner, inducing morphological changes and apoptosis. Transcriptomic analysis revealed substantial alterations in gene expression, including enrichment of metabolic pathways, DNA damage responses, and iron ion binding. Nitroxoline treatment upregulated genes involved in DNA repair and oxidative stress response while regulating genes in the methionine and cysteine cycles. It also decreased the mitochondrial membrane potential, H₂S production, and total iron amount in A. castellanii. Bioinformatic analyses and molecular docking studies suggest direct interactions between nitroxoline and several A. castellanii proteins. Our research provides a comprehensive molecular map of the response of A. castellanii to nitroxoline, revealing significant changes in gene expression related to the stress response and metabolic pathways. These findings underscore the potential of nitroxoline as a potent anti-Acanthamoeba agent, offering new insights into its mechanism of action and paving the way for effective combinational therapeutic strategies.

Fatal amoebic meningoencephalitis caused by Balamuthia mandrillaris in Pongo pygmaeus and first case report in Pan troglodytes verus

Balamuthia mandrillaris is an amoeba that can cause granulomatous amoebic encephalitis (GAE) as well as lung and skin infections in both humans and animals. Studies on B. mandrillaris-related GAE cases have increased in recent years. This amoeba has been identified as a cause of encephalitis and death in several non-human primates. In this study, we report a case of a 4-year-old female Bornean orangutan (Pongo pygmaeus) in a zoological center that exhibited neurological symptoms for several days. After unsuccessful treatments and a worsening in her condition, euthanasia was deemed necessary. Additionally, we describe the case of a 4-year-old male chimpanzee (Pan troglodytes verus) who died suddenly in a different zoo. Postmortem analysis revealed brain lesions with multiple hemorrhages, oedema, and inflammation in various organs in both cases. Histology showed the presence of B. mandrillaris trophozoites in necrotic and inflamed brain tissues, consistent with granulomatous amoebic meningoencephalitis. The diagnosis was confirmed using a multiplex qPCR assay on brain tissue samples from both animals water and soil samples from the chimpanzee's and orangutan's enclosure tested positive for B. mandrillaris DNA by qPCR, confirming environmental exposure. An immunofluorescent antibody (IFA) assay detected B. mandrillaris in chimpanzee brain slices. According to the authors' knowledge, this report documents the first known cases of Balamuthia amoebic encephalitis in non-human primates in Spain and the first case in Pan troglodytes verus.

Identification of Naegleria fowleri antigens recognized by serum antibodies from people of Mexicali Valley, México

Naegleria fowleri is an amoeba that causes a fatal disease in the central nervous system known as primary amoebic meningoencephalitis (PAM) in humans. Most of the infections are acquired by people who practice recreational activities in water contaminated with trophozoites. Swimming and wading in irrigation channels of Mexicali are common practices for local people. Although there are some warning signposts in the surrounding sites, people continue using these channels for recreational purposes. In that region, cases of PAM have been reported; however, not everyone who comes into contact with contaminated water containing trophozoites becomes infected, and the factors influencing their immune response to N. fowleri remain unknown. We analyzed the levels of antibodies against N. fowleri in two groups: local individuals, including visitors who swam in the Mexicali channels, and a group from Mexico City (CDMX). In both groups, specific antibody responses were analyzed using immunoassays, including Western blot, ELISA, and cytochemistry. The highest levels of both IgG and IgA were found in samples from Mexicali, compared to those from CDMX. In both groups, IgG recognized polypeptide bands from N. fowleri at molecular weights of 100, 50, and 19 kDa, bands that we have already reported as immunogenic. Moreover, the IgG subjects recognized trophozoite structures such as membrane, pseudopodia, food cups, and even small like-vesicles. This antibody immune response directed against these polypeptide bands and trophozoite structures along with other factors could be participating in the defense of these people against PAM.

Encystment and Excystment Processes in Acanthamoeba castellanii: An Emphasis on Cellulose Involvement

The free-living amoeba Acanthamoeba castellanii is a unicellular eukaryote distributed in a wide range of soil or aquatic environments, either natural or human-made, such as rivers, lakes, drinking water, or swimming pools. Besides its capacity to transport potential pathogens, such as bacteria or viruses, Acanthamoeba spp. can have intrinsic pathogenic properties by causing severe infections at the ocular and cerebral level, named granulomatous amoebic encephalitis and amoebic keratitis, respectively. During its life cycle, A. castellanii alternates between a vegetative and mobile form, named the trophozoite, and a resistant, latent, and non-mobile form, named the cyst. The cyst wall of Acanthamoeba is double-layered, with an inner endocyst and an outer ectocyst, and is mainly composed of cellulose and proteins. The resistance of cysts to many environmental stresses and disinfection treatments has been assigned to the presence of cellulose. The current review aims to present the importance of this glycopolymer in Acanthamoeba cysts and to further report the pathways involved in encystment and excystment.

Climate change will amplify the impacts of harmful microorganisms in aquatic ecosystems

More than 70% of the human population lives within five kilometres of a natural water feature. These aquatic ecosystems are heavily used for resource provision and recreation, and represent the interface between human populations and aquatic microbiomes, which can sometimes negatively impact human health. Diverse species of endemic aquatic microorganisms, including toxic microalgae and pathogenic bacteria, can be harmful to humans. Aquatic ecosystems are also subject to intrusions of allochthonous pathogenic microorganisms through pollution and runoff. Notably, environmental processes that amplify the abundance and impact of harmful aquatic microorganisms are occurring with increasing frequency owing to climate change. For instance, increases in water temperature stimulate outbreaks of pathogenic and toxic species, whereas more intense precipitation events escalate microbial contamination from stormwater discharge. In this Perspective we discuss the influence of aquatic microbiomes on the health and economies of human populations and examine how climate change is increasing these impacts.

A Balamuthia amoebic encephalitis survivor in China, and literature review

Balamuthia amoebic encephalitis (BAE) is a rare, fatal parasitic infection of the central nervous system, with a current mortality rate above 95%. The high fatality rate is largely attributed to atypical clinicopathological features, delayed diagnosis, and the absence of effective treatment methods, so quick recognition of this disease is vital. In this paper, we present a survivor of BAE, who was confirmed through histologic examination and metagenomic next-generation sequencing (mNGS) of brain lesions. This case, unlike most previous reports, was a successful survival case. It highlights the critical need for differential diagnosis in patients with central nervous system infectious diseases, particularly those with a history of skin lesions and patients presenting multifocal brain lesions. Moreover, mNGS could serve as a useful tool in rapid identification of causative rare pathogens. The application of decompressive craniectomy may offer treatment opportunities and improve the survival rate of BAE. The case description was followed by a review of the literatures, in order to improve clinicians' understanding of this disease.

Life-threatening dermatoses

Although rare, life-threatening dermatoses encompass various inflammatory, infectious, vasculitic/vasculopathy, paraneoplastic, and neoplastic skin diseases. Complications include skin barrier dysfunction, secondary infection, and internal organ involvement. Skin signs may serve as a critical window into systemic disease. Life-threatening dermatoses are typically associated with "red flag" clinical signs or symptoms, which inform the dermatologist about the severity of the disease and mandate a thorough history, review of systems, physical examination, and laboratory evaluation. This contribution highlights severe cutaneous adverse reactions, infections, vasculitides and vasculopathies, and paraneoplastic eruptions. Dermatologists should recognize life-threatening dermatoses and have a framework for rapid diagnosis and management.

Cloning of nf-profilin and intercellular interaction with nf-actin in Naegleria fowleri cysts

Naegleria fowleri is a free-living amoeba found in lakes, soil, hot springs, and poorly chlorinated swimming pools. It is pathogenic to humans, causing a rare and fatal brain infection known as primary amoebic meningoencephalitis (PAM). A previous study utilized RNA-seq analysis to examine genes expressed in N. fowleri cysts and trophozoites, focusing on the nf-profilin gene, which showed high expression in cysts. Profilin is a small actin-binding protein that regulates nf-actin polymerization and cell movement. Sequence analysis revealed 83% similarity with non-pathogenic N. gruberi and 38% similarity with Acanthamoeba castellanii. Nf-profilin was found to be associated with N. fowleri lysates but not with lysates from other amoebae, as shown by Western blot analysis. Immunofluorescence assays demonstrated that nf-profilin primarily localized to the cell membrane in N. fowleri cysts, while nf-actin localized to the cytoplasm, pseudopodia, and food-cup structures. Real-time RT-PCR indicated higher expression of the nf-profilin gene in cysts compared to trophozoites. In co-culture experiments with target cells, Nf-profilin was initially expressed in the cytoplasm of N. fowleri cysts and the morphology of cyst gradually transitioned to the trophozoite form. Concurrently, the expression of Nf-profilin protein decreased, while Nf-actin protein began to appear in the pseudopodia and food-cups of trophozoites. In conclusion, the nf-profilin and nf-actin genes exhibited complementary expression patterns based on the life stage of N. fowleri, indicating their critical roles in the survival and proliferation. This study emphasizes the significance of actin-binding proteins in understanding the infection and pathogenic mechanisms of N. fowleri.

Free-living amoebae: a journey into historical aspects and to current discoveries

Free-living amoebas (FLA) are ubiquitous protists found in the environment. They have shown exceptional resistance to environmental challenges and play significant roles in controlling microbial populations through their predatory behaviour and microbicidal activity in both soil and aquatic ecosystems environments. However, although rare, a limited group of FLA can cause serious infections in the central nervous system and other diseases, particularly in immunocompromised individuals with high mortality rates. They can also cause keratitis in otherwise healthy individuals. This review offers a comprehensive overview of freshwater naked amoebae but does not cover all aspects in detail. Its goal is to provide a historical context for our current understanding while addressing the most critical elements of FLA biology, their pathogenic potential, and their interactions with important human pathogens.

Phosphonium chloride-based deep eutectic solvents inhibit pathogenic Acanthamoeba castellanii belonging to the T4 genotype

Herein, we investigated the anti-amoebic activity of phosphonium-chloride-based deep eutectic solvents against pathogenic Acanthamoeba castellanii of the T4 genotype. Deep eutectic solvents are ionic fluids composed of two or three substances, capable of self-association to form a eutectic mixture with a melting point lower than each substance. In this study, three distinct hydrophobic deep eutectic solvents were formulated, employing trihexyltetradecylphosphonium chloride as the hydrogen bond acceptor and aspirin, dodecanoic acid, and 4-tert-butylbenzoic acid as the hydrogen bond donors. Subsequently, all three deep eutectic solvents, denoted as DES1, DES2, DES3 formulations, underwent investigations comprising amoebicidal, adhesion, excystation, cytotoxicity, and cytopathogenicity assays. The findings revealed that DES2 was the most potent anti-amoebic agent, with a 94% elimination rate against the amoebae within 24 h at 30 °C. Adhesion assays revealed that deep eutectic solvents hindered amoebae adhesion to human brain endothelial cells, with DES2 exhibiting 88% reduction of adhesion. Notably, DES3 exhibited remarkable anti-excystation properties, preventing 94% of cysts from reverting to trophozoites. In cytopathogenicity experiments, deep eutectic solvent formulations and dodecanoic acid alone reduced amoebae-induced human brain endothelial cell death, with DES2 showing the highest effects. Lactate dehydrogenase assays revealed the minimal cytotoxicity of the tested deep eutectic solvents, with the exception of trihexyltetradecylphosphonium chloride, which exhibited 35% endothelial cell damage. These findings underscore the potential of specific deep eutectic solvents in combating pathogenic Acanthamoeba, presenting promising avenues for further research and development against free-living amoebae.

Enlightening the promising role of nanoparticle-based treatments against Naegleria fowleri-induced primary amoebic meningoencephalitis: A brain-eating disease

Naegleria fowleri, is the causative agent of Primary Amoebic Meningoencephalitis (PAM), a lethal acute brain inflammation with high mortality. The virulent and reproductively active trophozoite stage of N. fowleri migrates to central nervous system (CNS) by entering through nasal passage and causes severe neural infection, brain disease and inflammation with high mortality. In this review we present the current available information about N. fowleri, including its case reports, pathogenesis and the mechanism of host neuroinflammation associated with PAM. Various case reports reveal that the survival rate of patients with PAM is very low. Several anti-microbial, anti-parasitic and anti-inflammatory compounds such as doxycycline, amphotericin, acyclovir, miltefosine, ampicillin, ceftriaxone, azithromycin are widely used to treat PAM. Nanoparticles conjugated drug has now attracted better attention in dealing with free-living amoeba community. Conventional drugs are being conjugated with nanomaterials like gold (Au), sliver (Ag) etc. which have elicited better amoebicidal effect against N. fowleri than unconjugated drugs. This targeted strategy may prove helpful and possibly may reduce neural damage.

Amoebas: the omnipotent organism and silent assassin

Amoebas are characterized by their unique ability to exist both as free-living organisms and, occasionally, as parasites within host tissues, earning them the designation 'amphizoic amoebae'. While amoebic infections are less prevalent, their health impact can be tremendous, leading to several diseases. In low-income countries, poor sanitation and socioeconomic conditions significantly increase the risk of amoebic infections, particularly E. histolytica, which affects up to 50 million people and causes over 100,000 deaths each year. Diagnostic methods, including microscopy, serological tests, polymerase chain reaction, and the loop-mediated isothermal amplification assay, have improved the accuracy and timeliness of amoeba diagnosis. However, these methodologies are often cost-prohibitive for developing countries. Conversely, current treatments involve aggressive protocols using antibiotics, antifungals, and anticancer agents. However, the prognosis for severe infections such as Primary Amoebic Meningoencephalitis and Granulomatous Amebic Encephalitis remains poor. Despite advancements, effective treatments, and new low-cost therapeutic options are still being researched. Thus, the current review sought to provide a description of molecular aspects such as amoeba virulence factors and invasion processes, focusing on recent advances in the detection, identification, and treatment of associated diseases.

Secreted small RNAs of Naegleria fowleri are biomarkers for diagnosis of primary amoebic meningoencephalitis

Rapid and accurate diagnostics are needed to effectively detect and treat primary amoebic meningoencephalitis (PAM) caused by Naegleria fowleri (Nf). Delayed diagnosis and similarities to other causes of meningitis contribute to a case mortality rate of >97%. Thus, there is an unmet medical need for a non-invasive liquid biopsy diagnostic method. We sequenced Nf extracellular vesicles (EVs) and identified microRNAs, tRNAs and other small RNAs in Nf-EVs. From these data we selected two prevalent small RNAs as biomarker candidates. We developed an RT-qPCR assay and both small RNAs were detected in Nf-EVs and amoeba-conditioned media. In the mouse model of PAM both small RNA biomarkers were detected in 100% of mouse plasma samples at the end-stage of infection. Notably, smallRNA-1 was detected in the urine of infected mice at timepoints as early as 24h post infection (18/23 mice) and in the plasma as early as 60h post infection (8/8 mice). Additionally, smallRNA-1 was detected in 100% (n=6) of CSF samples from human PAM cases, and in whole blood samples, but not in human plasma from PAM cases. In this study, we discovered small RNAs as biomarkers of Nf infection, one which can be detected reliably in CSF, urine, and whole blood. The RT-qPCR assay is a highly sensitive diagnostic assay that can be conducted in ~3h after receipt of liquid biopsy. The data suggest detection of smallRNA-1 biomarker could provide earlier diagnosis of PAM and be used to monitor biomass of amoebae during treatment.

Detection and identification of Naegleria species along with Naegleria fowleri in the tap water samples

Naegleria fowleri, the causative agent of Primary Amoebic Meningoencephalitis (PAM), is commonly found in warm freshwater environments and can enter the brain through nasal passages during activities like swimming or ablution. PAM has a high fatality rate, raising concerns about its global health impact. In Pakistan, particularly in Karachi, a significant number of cases have been reported, often with no history of recreational water exposure, but with regular ablution using tap water. This study analyzed the physicochemical parameters, abundance of total and fecal coliforms, and detected N. fowleri and other Naegleria species in tap water samples from Karachi using PCR with ITS- and Naegl-primers. Almost all samples exhibited high temperatures, low chlorine levels, and a high presence of coliforms. N. fowleri and other Naegleria species were detected in 11 out of 39 samples. Sequence analysis identified N. fowleri in tap water from the Golimar and Lyari areas of Karachi, while the other nine samples revealed different Naegleria species. This study suggests that the combination of high temperatures, insufficient chlorination, and the presence of coliforms may create favorable conditions for N. fowleri growth. However, these factors are not exclusive to the Golimar and Lyari areas, indicating that other environmental or infrastructural factors, not detailed in this study, may have contributed to the presence of N. fowleri in that specific location.

Identification and Characterization of Acanthamoeba from Contact Lens Care Solutions and Hospital Environments in the Ophthalmology Wards and Operating Rooms in Southeastern Iran

OBJECTIVE

Different Acanthamoeba species are among the most ubiquitous organisms causing serious diseases in humans including central nervous system (CNS) and eye infections. Contact lenses, lens care solutions and the hospital environments particularly the indoor and outdoor environments of ophthalmology wards where people are present with different types of eye diseases, are the potential sources of human infection. The purpose of the present study was the molecular investigation of free-living amoebae in the used contact lenses, lens care solutions and hospital samples from the ophthalmology wards and operating rooms in a referral hospital in southeastern Iran.

METHODS

Samples were collected from the lens care solutions, used contact lenses, and from indoor and outdoor environments of the ophthalmology ward and operating room of a major referral hospital in Kerman, Southeastern Iran. The samples were cultured on non-nutrient agar (NNA) in 28-30oC and microscopically studied. Molecular study including PCR-sequencing and phylogenetic analysis on partial 18 S rDNA were performed on positive culture samples.

RESULT

In total 70 samples were collected from the used contact lenses and lens care solutions, as well as the hospital environment of which 11.4% (8 out of 70) were found positive using NNA culture. Two out of 40 samples (5.0%) from the used contact lenses and the care solutions were found positive for the presence of Acanthamoeba T4 genotype. Acanthamoeba cysts were identified in two out of 22 dust samples (9.1%) collected from the ophthalmology ward and operating rooms. Protacanthamoeba bohemica was found in the soil samples from outdoor environment of the ophthalmology ward.

CONCLUSION

This study identified Acanthamoeba species in contact lenses and in indoor environmental samples from the ophthalmology ward. T4 genotype was found on the contact lenses examined in this study. In the dust sampled from within the ophthalmology ward Acanthamoeba sp. was identified.

Naegleria fowleri: Portrait of a Cerebral Killer

Background: Primary amebic meningoencephalitis (PAM) caused by Naegleria fowleri is a rare and devastating infection of the central nervous system, often diagnosed late, due to its rapid progression and nonspecific symptoms. Case Presentation: We report one of the youngest documented pediatric Vietnamese cases of PAM in a 10-month-old girl from the Mekong Delta, Vietnam. The diagnosis was confirmed through multiplex real-time PCR (MPL-rPCR), microscopy, and sequencing. Clinical data were gathered retrospectively from medical records, and additional details were provided by the patient's family. Treatment regimens, disease progression, and diagnostic challenges were reviewed and compared to existing literature. With intensive treatment, the child survived for 14 days, representing one of the longest reported pediatric PAM survival durations. No direct exposure to untreated freshwater or other typical risk factors for Naegleria fowleri infection was identified, underscoring the unique epidemiological nature of this case. MPL-rPCR enabled timely detection of the pathogen and demonstrated its utility in resource-limited settings. Conclusions: This case highlights the critical need for rapid, accessible diagnostic tools such as MPL-rPCR, particularly in resource-constrained environments where traditional diagnostics may not be feasible. It also emphasizes the importance of international collaboration and investment in cost-effective diagnostics and novel therapeutic strategies. The geographical expansion of PAM due to climate change further underscores the urgency of these measures to improve health outcomes in vulnerable populations.

Modes and mechanisms for the inheritance of mitochondria and plastids in pathogenic protists

Pathogenic protists are responsible for many diseases that significantly impact human and animal health across the globe. Almost all protists possess mitochondria or mitochondrion-related organelles, and many contain plastids. These endosymbiotic organelles are crucial to survival and provide well-validated and widely utilised drug targets in parasitic protists such as Plasmodium and Toxoplasma. However, mutations within the organellar genomes of mitochondria and plastids can lead to drug resistance. Such mutations ultimately challenge our ability to control and eradicate the diseases caused by these pathogenic protists. Therefore, it is important to understand how organellar genomes, and the resistance mutations encoded within them, are inherited during protist sexual reproduction and how this may impact the spread of drug resistance and future therapeutic approaches to target these organelles. In this review, we detail what is known about mitochondrial and plastid inheritance during sexual reproduction across different pathogenic protists, often turning to their better studied, nonpathogenic relatives for insight.

Development of a novel encystment medium: Enhancing diagnostic potential of Acanthamoeba spp

Background and Aim

Acanthamoeba spp. are pathogenic microorganisms linked to severe infections in humans and animals, requiring a deeper understanding of their encystation process for effective diagnostics and research. This study focused on developing a novel encystment medium to induce synchronized encystation of Acanthamoeba spp. efficiently and rapidly.

Materials and Methods

The study employed response surface methodology with a central composite design to optimize the encystment medium formulation. The key components included Tris-HCl, NaCl, glucose, and MgCl2. The optimized liquid medium was spray-dried to produce a dehydrated powder for practical application. The encystation efficiency of different Acanthamoeba strains was assessed using hemocytometry and fluorescence microscopy.

Results

The optimized medium, comprising 3.152 g/L Tris-HCl, 5.55 g/L NaCl, 8% (w/v) glucose, and 5.0 mM MgCl2 at pH 9.0, demonstrated exceptional encystation efficiency with rates ranging from 99% to 100%. A spray-dried powdered version of this medium was equally effective, achieving a 98.77% encystation rate for A. castellanii American Type Culture Collection 50739 in glucose-free conditions. Notably, optimal glucose concentrations varied among Acanthamoeba strains, with certain strains reaching maximum encystation at 6-8% glucose.

Conclusion

This study successfully developed an innovative encystment medium that promotes rapid and efficient cyst production in Acanthamoeba spp. The medium enhances laboratory research and diagnostic capabilities, paving the way for future advancements in understanding and managing Acanthamoeba infections.

Transcriptomic profiling of "brain-eating amoeba" Naegleria fowleri infection in mice: the host and the protozoa perspectives

The free-living amoeba Naegleria fowleri (NF) causes a rare but lethal parasitic meningoencephalitis (PAM) in humans. Currently, this disease lacks effective treatments and the specific molecular mechanisms that govern NF pathogenesis and host brain response remain unknown. To address some of these issues, we sought to explore naturally existing virulence diversity within environmental NF isolates. Herein, we purified two new NF environmental isolates (NF45 and NF1) and tested their in vivo virulence using experimental infection in mice. We found that NF45 was highly virulent (NF45_HV) compared with NF1 (low virulence, NF1_LV), based on in vivo amoeba growth kinetics and mouse survival. To identify underlying differences, we conducted RNA-seq and bioinformatics analyses from the infected mouse brains. Our results showed that NF1_LV and NF45_HV modulated the expression of their genes during mouse brain infection. Differentially expressed genes (DEGs) in NF1_LV were mostly involved in Translational protein, Protein-binding activity modulator, Protein modifying enzyme, while DEGs in NF45_HV were related to DNA metabolism, Cytoskeletal protein, Protein-binding activity modulator. Proteases (namely the virulence factor Cathepsin B) were upregulated in NF1_LV, while downregulated in NF45_HV. When analyzing the host response against infection by these two NF strains, enrichment analyses uncovered genes and mechanisms related to the host immune responses and nervous systems. We detected more DEGs in NF1_LV infected mice compared to NF45_HV, related to blood brain barrier leakage, immune cell recruitment, cytokine production (including IL-6, IFN-Ɣ and TNFα), inflammation of astrocytes and microglia, and oligodendrocyte and neurons degeneration. Increased expression of neuromotor-related genes such as Adam22, Cacnb4 and Zic1 (activated by NF1_LV infection) and ChAt (activated by NF45_LV infection) could explain PAM symptoms such as muscle weakness and seizures. Globally, our results showed that NF isolated from the environment can have different levels of virulence and differentially modulate their gene expression during brain infection. We also provided, for the first time, a comprehensive information for the molecular mechanisms of neuro-immune and host-pathogen interactions during PAM disease. As the host and the protozoa are strongly implicated in PAM lethality, new therapies targeting both the parasite, and the host should be considered to treat PAM infection.

"Nano knife" for efficient piezocatalytic inactivation of amoeba spores and their intracellular bacteria: Synergetic effect between physical damage and chemical oxidation

Microbial interactions between infectious agents severely interfere with the disinfection process, and current disinfection methods are unable to effectively inactivate intracellular pathogens, posing a new threat to drinking water safety. In this study, we first reported the high efficiency of piezocatalysis in inactivating amoebae and their intracellular bacteria. Results showed that the inactivation rates of the MoS2/rGO piezocatalytic system for amoebic spores and their intracellular bacteria were 4.18 and 5.02-log, respectively, within 180 min. Based on scavenger studies and ESR tests, the efficient inactivation of pathogens can be attributed to the generation of reactive oxygen species (ROS), and different pathogens exhibit varying tolerances to distinct ROS. Moreover, TEM analysis revealed that the sharp edge of MoS2/rGO was conducive to the physical cutting of amoeba's cell wall and membrane, promoting the attack of ROS and ensuring a more thorough deactivation. Additionally, the intracellular ROS produced by amoebae is not only conducive to the inactivation of amoebae but also the main reason for the inactivation of bacteria in spores. This study provides a new solution for the inactivation of amoeba spores and their intracellular bacteria and emphasizes the high efficiency of the synergistic effect of physical damage and chemical oxidation.

Targeting pathogenic Acanthamoeba castellanii using DNA minor groove binding agents

DNA minor groove binders exhibit a high degree of sequence specificity and have a variety of biological actions including antiviral, anticancer, antibacterial, and anti-protozoal properties. Since it is the location of non-covalent interactions, the minor groove of double helical B-DNA is gaining significant interest as therapeutic targets. For the purpose of this investigation, the synthesis of five novel DNA minor groove binding agents was accomplished and antiparasitic efficacies were determined against Acanthamoeba castellanii of the T4 genotype in vitro. Using amoebicidal assays, the results revealed that all inhibitors tested showed significant killing of amoebae (P < 0.05). Pre-treatment of amoebae with DNA minor groove binders inhibited parasite-mediated human cell death by measuring lactate dehydrogenase release using cytopathogenicity assays. Cytotoxicity assays revealed minimal effects on human cells. As phenotypic switching leads to infection recurrence, assays revealed that inhibitors blocked amoebae phenotypic transformation. These are promising findings and suggest that DNA minor groove binders may hold promise for further research in the effective eradication of pathogenic A. castellanii.

Amoebicidal and cysticidal in vitro activity of cationic dendritic molecules against Acanthamoeba polyphaga and Acanthamoeba griffini

Acanthamoeba species are responsible for serious human infections, including Acanthamoeba keratitis (AK) and granulomatous amoebic encephalitis (GAE). These pathogens have a simple life cycle consisting of an infective trophozoite stage and a resistant cyst stage, with cysts posing significant treatment challenges due to their resilience against harsh conditions and chemical agents. Current treatments for AK often involve combining diamines, such as propamidine, and biguanides, such as chlorhexidine (CLX), which exhibit limited efficacy and significant toxicity. Thus, the effect of new therapeutic molecules, such as multifunctional systems (e.g., carbosilane dendritic molecules), should be studied as potential alternatives due to their biocidal properties and lower toxicity. This study evaluates various dendritic compounds against trophozoites and cysts of two Acanthamoeba clinical isolates, both alone and in combination with CLX, and assesses their cytotoxicity on HeLa cells. The results indicated that certain dendritic compounds, especially BDSQ024, were effective against both trophozoites and cysts. Additionally, combinations of dendritic molecules and CLX showed enhanced efficacy in eliminating trophozoites and cysts, suggesting potential for synergistic treatments. The study underscores the promise of dendritic molecules in developing more effective and less toxic therapies for Acanthamoeba infections.

Detection and Confirmation of Naegleria fowleri in a Primary Amebic Meningoencephalitis Patient Using a Molecular Approach

The Naegleria fowleri amoeba stands as the primary culprit behind primary amebic meningoencephalitis (PAM), presenting a substantial global public health concern. In recent years, over 17 cases of PAM have been reported in Karachi, Pakistan, highlighting its increased prevalence in the country's most densely populated city. This study scrutinized 74 cerebrospinal fluid (CSF) samples collected from meningitis patients across various health facilities in the city. These samples underwent thorough examination employing biochemical, microbial, and cytological methods. Additionally, polymerase chain reaction (PCR) with specific primers targeting the Naegleria genus and N. fowleri was employed to ascertain the presence of N. fowleri in the CSF samples. While biochemical and cytological analyses provided supportive information, they failed to yield a distinct diagnostic pattern. Nevertheless, through direct microscopic observation, cultural growth, and PCR-based analyses, N. fowleri was definitively identified in one CSF sample.

Application of ventriculoscopy in granulomatous amoebic encephalitis: a case report in China and literature review

Balamuthia mandrillaris is a kind of brain-eating amoeba leading to granulomatous amoebic encephalitis (GAE) with a high mortality rate and limited effective treatment options. Its underlying pathological mechanisms are still poorly understood. Here, we presented a 58-year-old man with Balamuthia mandrillaris meningoencephalitis, who died 33 days after onset. In this unique case, we introduced the use of ventriculoscopy in the treatment of B. mandrillaris meningoencephalitis. Through ventriculoscopy, we observed that the inflammatory response triggered by the disease was diffuse and extensive throughout the ventricles and meninges, not limited to the region of parasite invasion. Furthermore, under the precise guidance of ventriculoscopy, we implemented drug lavage therapy and intraventricular drainage, which, to a certain extent, managed to mitigate the progression of hydrocephalus and intracranial hypertension. Despite the unfortunate outcome of the patient's death due to brainstem hemorrhage, we reiterate the crucial role that surgical intervention plays in both diagnosing and managing amoebic encephalitis. This underscores the need for continued research and innovation in surgical techniques to enhance patient outcomes and combat this challenging neurological condition.

Drug modifications: graphene oxide-chitosan loading enhanced anti-amoebic effects of pentamidine and doxycycline

Acanthamoeba castellanii is the causative pathogen of a severe eye infection, known as Acanthamoeba keratitis and a life-threatening brain infection, named granulomatous amoebic encephalitis. Current treatments are problematic and costly and exhibit limited efficacy against Acanthamoeba parasite, especially the cyst stage. In parallel to drug discovery and drug repurposing efforts, drug modification is also an important approach to tackle infections, especially against neglected parasites such as free-living amoebae: Acanthamoeba. In this study, we determined whether modifying pentamidine and doxycycline through chitosan-functionalized graphene oxide loading enhances their anti-amoebic effects. Various concentrations of doxycycline, pentamidine, graphene oxide, chitosan-functionalized graphene oxide, and chitosan-functionalized graphene oxide loaded with doxycycline and pentamidine were investigated for amoebicidal effects against pathogenic A. castellanii belonging to the T4 genotype. Lactate dehydrogenase assays were performed to determine toxic effects of these various drugs and nanoconjugates against human cells. The findings revealed that chitosan-functionalized graphene oxide loaded with doxycycline demonstrated potent amoebicidal effects. Nanomaterials significantly (p < 0.05) inhibited excystation and encystation of A. castellanii without exhibiting toxic effects against human cells in a concentration-dependent manner, as compared with other formulations. These results indicate that drug modifications coupled with nanotechnology may be a viable avenue in the rationale development of effective therapies against Acanthamoeba infections.

Morphological Characterization and Genotyping of Acanthamoeba Isolates From Oral and Nasal Samples of Cancer Patients in Kashan, Iran

Background: Acanthamoeba species are recognized as the most prevalent free-living amoebae (FLA). They can cause granulomatous amebic encephalitis (GAE) and pulmonary and ocular infections. The present study aimed to isolate and identify Acanthamoeba genotypes in cancer patients referred to Kashan's hospitals in Central Iran. Methods: This cross-sectional study was conducted with oral and nasal swab samples collected from a hundred cancer patients referred to Kashan's Beheshti and Yasrebi hospitals during 2019-2020. The samples were cultured in 1.5% non-nutrient agar (NNA) with heat-killed Escherichia coli and examined for "FLA." A polymerase chain reaction (PCR) assay amplifying the 18S rRNA gene was performed, and Acanthamoeba-positive isolates were subjected to nucleotide sequencing to identify their genotypes. Results: The prevalence of Acanthamoeba infection was 51% in the oral cavity and 38% in the nasal samples of cancer patients. The most frequent Acanthamoeba cysts were (51.3%) wrinkled polygonal and sized 9.55-11.5 μm (Group II). Acanthamoeba genotypes T4, T11, and T5 were identified in the oral cavity samples, whereas T4 and T11 were detected in the nasal samples. Conclusion: The prevalence of Acanthamoeba infection in oral and nasal cancer patients was higher in Kashan, Iran, compared to other countries. Due to the high rate of oral Acanthamoeba contamination, oral sampling is recommended for better detection of this protozoan. Since T4 is the predominant genotype that can cause serious diseases in high-risk groups, increasing physicians' awareness of infections associated with Acanthamoeba and preventive and control measures are strongly suggested.

Odontites linkii subsp. cyprius Ethanolic Extract Indicated In Vitro Anti-Acanthamoeba Effect

This study aims to investigate three endemic ethanolic leaf extracts from Cyprus for anti-Acanthamoeba activities: Odontites linkii subsp. cyprius (Boiss.) Bolliger, Ptilostemon chamaepeuce subsp. cyprius (Greuter) Chrtek & B. Slavík, and Quercus alnifolia Poech. Screening for radical scavenging activity, total phenolic content (TPC), and total flavonoid content (TFC) were performed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABST) methods, Folin-Ciocalteu method, and aluminum chloride method, respectively. An antibacterial-susceptibility test (AST) was performed using a broth microdilution assay to estimate the minimum inhibitory concentration (MIC) using iodonitrotetrazolium chloride (INT). Trypan blue (0.5%) was used to assess in vitro anti-Acanthamoeba cell viability of the ethanolic leaf extracts after 24-, 48-, and 72-h exposure-screening of ethanolic leaf extracts with liquid chromatography-mass spectrometry (LC-MS) for known compounds with biological activity. The ethanolic leaf extract of Odontites linkii subsp. cyprius demonstrated the highest anti-Acanthamoeba activity, with an inhibitory concentration (IC50) of 7.02 mg/mL after 72 h. This extract also showed an in vitro minimum inhibitory concentration (MIC) of 0.625 mg/mL against Enterococcus faecalis, a common nosocomial pathogen. The LC-MS analysis revealed the presence of bioactive iridoid compounds in O. linkii subsp. cyprius, further highlighting its potential as a source for new drug compounds. The ethanolic extract of O. linkii subsp. cyprius demonstrated a dose-dependent and time-dependent anti-Acanthamoeba effect in vitro. This study is the first to report the presence of iridoid compounds and anti-Acanthamoeba activities in the ethanolic extract of O. linkii subsp. cyprius. These promising findings highlight the potential of plant extracts, particularly O. linkii subsp. cyprius, as a source for new drug compounds for Acanthamoeba infections.

Potentially Pathogenic Free-Living Amoebae Isolated from Soil Samples from Warsaw Parks and Squares

Free-living amoebae (FLA) are prevalent in diverse environments, representing various genera and species with different pathogenicity. FLA-induced infections, such as the highly fatal amoebic encephalitis, with a mortality rate of 99%, primarily affect immunocompromised individuals while others such as Acanthamoeba keratitis (AK) and cutaneous amebiasis may affect immunocompetent individuals. Despite the prevalence of FLA, there is a lack of standardized guidelines for their detection near human habitats. To date, no studies on the isolation and identification of FLA in environmental soil samples in Warsaw have been published. The aim of this study was to determine the presence of amoebae in soil samples collected from Warsaw parks and squares frequented by humans. The isolated protozoa were genotyped. Additionally, their pathogenic potential was determined through thermophilicity tests. A total of 23 soil samples were seeded on non-nutrient agar plates (NNA) at 26 °C and monitored daily for FLA presence. From the total of 23 samples, 18 were positive for FLA growth in NNA and PCR (78.2%). Acanthamoeba spp. was the most frequently isolated genus, with a total of 13 positive samples (13/18; 72.2%), and the T4 genotype being the most common. Moreover, Platyamoeba placida (3/18; 16.7%), Stenamoeba berchidia (1/18; 5.6%) and Allovahlkampfia sp. (1/18; 5.6%), also potentially pathogenic amoebae, were isolated. To our knowledge, this is the first report of FLA presence and characterization in the Warsaw area.

Anti-Acanthamoebic effects of silver-conjugated tetrazole nanoparticle

Tetrazoles are five-membered ring aromatic heterocyclic molecules that consist of one carbon and four nitrogen atoms. Several tetrazole-based drugs have shown promising activities against bacteria, fungi, asthma, cancer, hypertension etc. The overall aim of this study was to determine anti-Acanthamoebic properties of tetrazoles and tetrazole-conjugated silver nanoparticles. Tetrazole-conjugated silver nanoparticles were synthesized and confirmed using ultraviolet-visible spectrometry, Dynamic light scattering, and Fourier-transform infrared spectroscopy. Using amoebicidal, encystment, and excystment assays, the findings revealed that tetrazoles exhibited antiamoebic properties and these effects were enhanced when conjugated with silver nanoparticles. Importantly, conjugation with silver nanoparticles inhibited parasite-mediated human cell death in vitro, as measured by lactate dehydrogenase release, but it reduced toxic effects of drugs alone on human cells. Overall, these results showed clearly that tetrazoles exhibit potent antiamoebic properties which can be enhanced by conjugation with silver nanoparticles and these potential in the rational development of therapeutic interventions against parasitic infections such as keratitis and granulomatous amoebic encephalitis due to pathogenic Acanthamoeba.

Synthesis and Biological Evaluation of Cyanoacrylamides and 5-Iminopyrrol-2-Ones Against Naegleria fowleri

Primary amoebic meningoencephalitis is caused by the free-living amoeba Naegleria fowleri. The lack of standardized treatment has significantly contributed to the high fatality rates observed in reported cases. Therefore, this study aims to explore the anti-Naegleria activity of eight synthesized cyanoacrylamides and 5-iminopyrrol-2-ones. Notably, QOET-109, QOET-111, QOET-112, and QOET-114 exhibited a higher selectivity index against Naegleria compared to those of the rest of the compounds. Subsequently, these chemicals were assessed against the resistant stage of N. fowleri, demonstrating activity similar to that observed in the vegetative stage. Moreover, characteristic events of programmed cell death were evidenced, including chromatin condensation, increased plasma membrane permeability, mitochondrial damage, and heightened oxidative stress, among others. Finally, this research demonstrated the in vitro activity of the cyanoacrylamide and 5-iminopyrrol-2-one molecules, as well as the induction of metabolic event characteristics of regulated cell death in Naegleria fowleri.

Reliable and specific detection of Acanthamoeba spp. in dishcloths using quantitative real-time PCR assay

Acanthamoeba spp., are ubiquitous protist which belongs to Free-Living Amoeba (FLA) group, is considered as causal agent of side-threatening keratitis or fatal encephalitis among other human infections. Besides, this parasite has been reported as host for other microorganisms important to human health such as Campylobacter spp. or Vibrio spp. among others. This role of Acanthamoeba as pathogen and environmental phagocyte has increased the reports confirming its presence in human related environments, acting as a water quality indicator. Considering the tide relationship between water and kitchen environments, and the high prevalence of Acanthamoeba in water sources, the present study aims to establish a quick and accurate protocol based on DNA extraction and a real time qPCR assay to detect Acanthamoeba spp. in dishcloths. The procedure has been validated by processing 17 used dishcloths. Our findings demonstrated the high sensitivity of the qPCR assay used which was capable of detecting up to one Acanthamoeba from an in vitro contaminated dishcloth. The protocol accurately detected 64.7% of positive samples for Acanthamoeba spp, (in 4 samples DNA concentrations corresponded to 1-102 amoebae). Our findings demonstrate the importance of FLA surveillance by efficient and sensitive methods since one amoeba is capable of colonizing human related food environments such as kitchens sinks and could be a potential source of infection.

Approaches for Targeting Naegleria fowleri Using Nanoparticles and Artificial Peptides

Naegleria fowleri is a free-living amoeba which causes primary amoebic meningoencephalitis (PAM). Although PAM is rare, the fatality rate is staggering at over 97%. So, the importance of finding an effective treatment and cure for PAM caused by N. fowleri is a crucial area of research. Existing research on developing novel therapeutic strategies to counter N. fowleri infection is limited. Since the blood-brain barrier (BBB) presents an obstacle to delivering drugs to the site of infection, it is important to employ strategies that can effectively direct the therapeutics to the brain. In this regard, our review focuses on understanding the physiology and mechanisms by which molecules pass through the BBB, the current treatment options available for PAM, and the recent research conducted in the decade of 2012 to 2022 on the use of nanomaterials to enhance drug delivery. In addition, we compile research findings from other central nervous system (CNS) diseases that use shuttle peptides which allow for transport of molecules through the BBB. The approach of utilizing BBB shuttles to administer drugs through the BBB may open up new areas of drug discovery research in the field of N. fowleri infection.

Diversity of Free-Living Amoebae in New Zealand Groundwater and Their Ability to Feed on Legionella pneumophila

Free-living amoebae (FLA) are common in both natural and engineered freshwater ecosystems. They play important roles in biofilm control and contaminant removal through the predation of bacteria and other taxa. Bacterial predation by FLA is also thought to contribute to pathogen dispersal and infectious disease transmission in freshwater environments via the egestion of viable bacteria. Despite their importance in shaping freshwater microbial communities, the diversity and function of FLA in many freshwater ecosystems are poorly understood. In this study, we isolated and characterized FLA from two groundwater sites in Canterbury, New Zealand using microbiological, microscopic, and molecular techniques. Different methods for groundwater FLA isolation and enrichment were trialed and optimized. The ability of these isolated FLA to predate on human pathogen Legionella pneumophila was assessed. FLA were identified by 18S metagenomic amplicon sequencing. Our study showed that Acanthamoeba spp. (including A. polyphaga) and Vermamoeba veriformis were the main FLA species present in both groundwater sites examined. While most of the isolated FLA co-existed with L. pneumophila, the FLA populations in the L. pneumophila co-culture experiments predominantly consisted of A. polyphaga, Acanthamoeba spp., Naegleria spp., V. vermiformis, Paravahlkampfia spp., and Echinamoeba spp. These observations suggest that FLA may have the potential to act as reservoirs for L. pneumophila in Canterbury, New Zealand groundwater systems and could be introduced into the local drinking water infrastructure, where they may promote the survival, multiplication, and dissemination of Legionella. This research addresses an important gap in our understanding of FLA-mediated pathogen dispersal in freshwater ecosystems.

Ouabain, ATPase inhibitor, potentially enhances the effect of polyhexamethylene biguanide on Acanthamoeba castellanii

Acanthamoeba, a free-living amoeba, is commonly found in various natural environments, such as rivers and soil, as well as in public baths, swimming pools, and sewers. Acanthamoeba can cause severe illness such as granulomatous amoebic encephalitis and Acanthamoeba keratitis (AK) in humans. AK, the most recognized disease, can cause permanent visual impairment or blindness by affecting the cornea. AK commonly affects contact lens wearers who neglect proper cleaning habits. The symptoms of AK include epithelial and stromal destruction, corneal infiltrate, and intense ocular pain, occasionally necessitating surgical removal of the entire eyeball. Current AK treatment involves the hourly application of eye drops containing polyhexamethylene biocide (PHMB). However, studies have revealed their ineffectiveness against drug-resistant strains. Acanthamoeba can form cysts as a survival mechanism in adverse environments, though the exact mechanism remains unknown. Our experiments revealed that sodium P-type ATPase (ACA1_065450) is closely linked to encystation. In addition, various encystation buffers, such as MgCl2 or NaCl, induced the expression of P-type ATPase. Furthermore, we used ouabain, an ATPase inhibitor, to inhibit the Na+/K+ ion pump, consequently decreasing the encystation rate of Acanthamoeba. Our primary objective is to develop an advanced treatment for AK. We anticipate that the combination of ouabain and PHMB may serve as an effective therapeutic approach against AK in the future.

Assessment of pathogenic protozoa in a drinking water treatment plant with UV treatment

Controlling drinking water treatment processes is essential to address water contamination and the adaptability of certain pathogenic protozoa. Sometimes, standard treatment methods and chlorine disinfection may prove insufficient in eliminating pathogenic protozoa. However, ultraviolet (UV) radiation has proved to be more effective than chlorine. This study aims to characterize the eukaryotic community of a drinking water treatment plant that applies a final UV disinfection treatment, focusing on pathogenic protozoa. Fifty water samples (raw water, before and after UV treatment) were evaluated to comply with regulation parameters and identify relevant protozoa. Despite physicochemical and microbiological parameters meeting the regulation, some potentially pathogenic protozoa, such as Blastocystis or Cryptosporidium, were still detected in very low relative abundances in treated water. It was found for the first time in Spain the pathogenic amoebae Naegleria fowleri in one river water, which was not found after the treatment. Moreover, Blastocystis subtypes ST1-ST6 were detected in this study in raw, before and after UV water samples. Blastocystis was only found in 2 two samples after UV treatment, with a very low abundance (≤0.02%). Obtained results demonstrate the effectiveness of water treatment in reducing the prevalence of pathogenic protozoa.

First Report of Acanthamoeba Genotype T4 from the Newly Formed Tajogaite Volcano Tephra (La Palma, Canary Islands)

The Tajogaite Volcano erupted on the western slope of the Cumbre Vieja mountain range on La Palma Island in the Canary Islands, Spain, in 2021. As one of the multiple consequences of this eruption, a layer of tephra was deposited, to a variable extent, over a large part of the island. Tephra deposits affect all aspects of vegetation recovery, the water cycle, and the long-term availability of volcanic nutrients. Protozoa, including free-living amoeba (FLA), are known to be among the first microorganisms capable of colonizing harsh environments. In the present study, the presence of FLA has been evaluated in the Tajogaite Volcano deposits. Samples of the tephra were collected and incubated at 26 °C on 2% non-nutrient agar plates with a layer of heat-killed E. coli. Morphological features, as well as the DF3 region sequence of the 18S rDNA, confirmed the presence of a T4 genotype strain of Acanthamoeba. Thermotolerance and osmotolerance assays were used to evaluate the strain's pathogenic potential. This strain was considered thermotolerant but poorly osmotolerant. To the best of our knowledge, this is the first report of Acanthamoeba being isolated from a recently erupted volcano.