Successful Treatment of Confirmed Naegleria fowleri Primary Amebic Meningoencephalitis.

Primary amebic meningoencephalitis caused by Naegleria fowleri is a rare but nearly always fatal parasitic infection of the brain. Globally, few survivors have been reported, and the disease has no specific treatment. We report a confirmed case in Pakistan in a 22-year-old man who survived after aggressive therapy.

Case Report: A Series of Three Meningoencephalitis Cases Caused by Acanthamoeba spp. from Eastern India.

Acanthamoeba spp. are rare etiological agents of meningoencephalitis with high mortality. We present three cases of Acanthamoeba meningoencephalitis in immunocompetent individuals from Eastern India. The first patient presented with fever and headache; the second with headache, visual disturbance, and squint; and the third presented in a drowsy state. The cases presented on March 3, 18, and 21, 2023 respectively. The first two patients had concomitant tubercular meningitis for which they received antitubercular therapy and steroid. Their cerebrospinal fluid showed slight lymphocytic pleocytosis and increased protein. The diagnosis was done by microscopy, culture, and polymerase chain reaction. They received a combination therapy comprising rifampicin, fluconazole, and trimethoprim-sulfamethoxazole. The first patient additionally received miltefosine. She responded well to therapy and survived, but the other two patients died despite intensive care. Detection of three cases within a period of 1 month from Eastern India is unusual. It is imperative to sensitize healthcare providers about Acanthamoeba meningoencephalitis to facilitate timely diagnosis and treatment of the disease.

Primary amebic meningoencephalitis: a review of Naegleria fowleri and analysis of successfully treated cases.

Primary amebic meningoencephalitis (PAM) is a necrotizing and hemorrhagic inflammation of the brain and meninges caused by Naegleria fowleri, a free-living thermophilic ameba of freshwater systems. PAM remains a neglected disease that disproportionately affects children in tropical and subtropical climates, with an estimated mortality rate of 95-98%. Due to anthropogenic climate change, the average temperature in the USA has increased by 0.72 to 1.06 °C in the last century, promoting the poleward spread of N. fowleri. PAM is often misdiagnosed as bacterial meningitis or viral encephalitis, which shortens the window for potentially life-saving treatment. Diagnosis relies on the patient's history of freshwater exposure and the physician's high index of suspicion, supported by cerebrospinal fluid studies. While no experimental trials have been conducted to assess the relative efficacy of treatment regimens, anti-amebic therapy with adjunctive neuroprotection is standard treatment in the USA. We performed a literature review and identified five patients from North America between 1962 and 2022 who survived PAM with various degrees of sequelae.

High-Throughput Screen of Microbial Metabolites Identifies F1FO ATP Synthase Inhibitors as New Leads for Naegleria fowleri Infection.

Primary amebic meningoencephalitis (PAM), a brain infection caused by a free-living ameba Naegleria fowleri, leads to an extensive inflammation of the brain and death within 1-18 (median 5) days after symptoms begin. Although natural products have played a significant role in the development of drugs for over a century, research focusing on identifying new natural product-based anti-N. fowleri agents is limited. We undertook a large-scale ATP bioluminescence-based screen of about 10,000 unique marine microbial metabolite mixtures against the trophozoites of N. fowleri. Our screen identified about 100 test materials with >90% inhibition at 50 µg/mL and a dose-response study found 20 of these active test materials exhibiting an EC50 ranging from 0.2 to 2 µg/mL. Examination of four of these potent metabolite mixtures, derived from our actinomycete strains CNT671, CNT756, and CNH301, resulted in the isolation of a pure metabolite identified as oligomycin D. Oligomycin D exhibited nanomolar potency on multiple genotypes of N. fowleri, and it was five- or 850-times more potent than the recommended drugs amphotericin B or miltefosine. Oligomycin D is fast-acting and reached its EC50 in 10 h, and it was also able to inhibit the invasiveness of N. fowleri significantly when tested on a matrigel invasion assay. Since oligomycin is known to manifest inhibitory activity against F1FO ATP synthase, we tested different F1FO ATP synthase inhibitors and identified a natural peptide leucinostatin as a fast-acting amebicidal compound with nanomolar potency on multiple strains.

Natural Terpenes Inhibit the Cytopathogenicity of Naegleria fowleri Causing Primary Amoebic Meningoencephalitis in the Human Cell Line Model.

Naegleria fowleri is one of the free-living amoebae and is a causative agent of a lethal and rare central nervous system infection called primary amoebic meningoencephalitis. Despite the advancement in antimicrobial chemotherapy, the fatality rate in the reported cases is more than 95%. Most of the treatment drugs used against N. fowleri infection are repurposed drugs. Therefore, a large number of compounds have been tested against N. fowleri in vitro, but most of the compounds showed high toxicity. To overcome this, we evaluated the effectiveness of naturally occurring terpene compounds against N. fowleri. In this study, we evaluated the antiamoebic potential of natural compounds including Thymol, Borneol, Andrographolide, and Forskolin againstN. fowleri. Thymol showed the highest amoebicidal activity with IC50/24 h at 153.601 ± 19.6 µM. Two combinations of compounds Forskolin + Thymol and Forskolin + Borneol showed a higher effect on the viability of trophozoites as compared to compounds alone and hence showed a synergistic effect. The IC50 reported for Forskolin + Thymol was 81.30 ± 6.86 µM. Borneol showed maximum cysticidal activity with IC50/24 h at 192.605 ± 3.01 µM. Importantly, lactate dehydrogenase release testing revealed that all compounds displayed minimal cytotoxicity to human HaCaT, HeLa, and SH-SY5Y cell lines. The cytopathogenicity assay showed that Thymol and Borneol also significantly reduced the host cell cytotoxicity of pretreated amoeba toward the human HaCaT cell line. So, these terpene compounds hold potential as therapeutic agents against infections caused by N. fowleri and are potentially a step forward in drug development against this deadly pathogen as these compounds have also been reported to cross the blood-brain barrier. Therefore, an in vivo study using animal models is necessary to assess the efficacy of these compounds and the need for further research into the intranasal route of delivery for the treatment of these life-threatening infections.

Clinical manifestations and outcome of patients with primary amoebic meningoencephalitis in Pakistan. A single-center experience.

Primary amoebic meningoencephalitis (PAM) is a rapidly progressing central nervous system (CNS) infection caused by Naegleria fowleri, a free-living amoeba found in warm freshwater. The disease progression is very rapid, and the outcome is nearly always fatal. We aim to describe the disease course in patients admitted with PAM in a tertiary care center in Karachi, Pakistan between the periods of 2010 to 2021. A total of 39 patients were included in the study, 33 males (84.6%). The median age of the patients was 34 years. The most frequent presenting complaint was fever, which was found in 37 patients (94.9%) followed by headache in 28 patients (71.8%), nausea and vomiting in 27 patients (69.2%), and seizures in 10 patients (25.6%). Overall, 39 patients underwent lumbar puncture, 27 patients (69.2%) had a positive motile trophozoites on CSF wet preparation microscopy, 18 patients (46.2%) had a positive culture, and 10 patients had a positive PCR. CSF analysis resembled bacterial meningitis with elevated white blood cell counts with predominantly neutrophils (median, 3000 [range, 1350-7500] cells/µL), low glucose levels median, 14 [range, 1-92] mg/dL), and elevated protein levels (median, 344 [range, 289-405] mg/dL). Imaging results were abnormal in approximately three-fourths of the patients which included cerebral edema (66.7%), hydrocephalus (25.6%), and cerebral infarctions (12.8%). Only one patient survived. PAM is a fatal illness with limited treatment success. Early diagnosis and prompt initiation of treatment can improve the survival of the patients and reduce mortality.

Fatal Primary Amebic Meningoencephalitis due to Naegleria fowleri: The First Imported Case in Korea.

Primary amebic meningoencephalitis (PAM) is a rare, but almost always fatal, central nervous system infection caused by Naegleria fowleri, which are thermophilic free-living amoeba. Here, we report the first case of PAM detected in South Korea, probably imported from Thailand. Despite antimicrobial treatment for N. fowleri infection with a combination of intravenous liposomal amphotericin B, fluconazole, azithromycin, and oral rifampin, the patient died 13 days after the onset of symptoms. Clinicians in South Korea treating severe meningoencephalitis, especially in individuals returning from tropical areas, are encouraged to include PAM in the differential diagnoses, given the accelerated global warming and increased overseas trips.

The anti-amoebic potential of carboxamide derivatives containing sulfonyl or sulfamoyl moieties against brain-eating Naegleria fowleri.

Naegleria fowleri is a free-living thermophilic flagellate amoeba that causes a rare but life-threatening infection called primary amoebic meningoencephalitis (PAM), with a very high fatality rate. Herein, the anti-amoebic potential of carboxamide derivatives possessing sulfonyl or sulfamoyl moiety was assessed against pathogenic N. fowleri using amoebicidal, cytotoxicity and cytopathogenicity assays. The results from amoebicidal experiments showed that derivatives dramatically reduced N. fowleri viability. Selected derivatives demonstrated IC50 values at lower concentrations; 1j showed IC50 at 24.65 µM, while 1k inhibited 50% amoebae growth at 23.31 µM. Compounds with significant amoebicidal effects demonstrated limited cytotoxicity against human cerebral microvascular endothelial cells. Finally, some derivatives mitigated N. fowleri-instigated host cell death. Ultimately, this study demonstrated that 1j and 1k exhibited potent anti-amoebic activity and ought to be looked at in future studies for the development of therapeutic anti-amoebic pharmaceuticals. Further investigation is required to determine the clinical relevance of our findings.

Identification and characterization of novel marine oxasqualenoid yucatecone against Naegleria fowleri.

Naegleria fowleri is an opportunistic protozoan, belonging to the free-living amoeba group, that can be found in warm water bodies. It is causative agent the primary amoebic meningoencephalitis, a fulminant disease with a rapid progression that affects the central nervous system. However, no 100% effective treatments are available and those that are currently used involve the appearance of severe side effects, therefore, there is an urgent need to find novel antiamoebic compounds with low toxicity. In this study, the in vitro activity of six oxasqualenoids obtained from the red algae Laurencia viridis was evaluated against two different strains of N. fowleri (ATCC® 30808 and ATCC® 30215) as well as their cytotoxicity against murine macrophages. Yucatecone was the molecule with the highest selectivity index (>2.98 and 5.23 respectively) and it was selected to continue with the cell death type determination assays. Results showed that yucatone induced programmed cell death like responses in treated amoebae causing DNA condensation and cellular membrane damage among others. In this family of oxasqualenoids, it seems that the most significative structural feature to induce activity against N. fowleri is the presence of a ketone at C-18. This punctual oxidation transforms an inactive compound into a lead compound as the yucatecone and 18-ketodehydrotyrsiferol with IC50 values of 16.25 and 12.70 µM, respectively. The assessment of in silico ADME/Tox analysis revealed that the active compounds showed good Human Oral Absorption and demonstrate that are found to be within the limit of approved drug parameter range. Hence, the study highlights promising potential of yucatone to be tested for therapeutic use against primary amoebic meningoencephalitis.

Clinical Reasoning: A 67-Year-Old Man With Multiple Intracranial Lesions.

A wide variety of diseases present with intracranial lesions. In this case report, a 67-year-old man initially presented to an outside hospital with nausea, headache, and ataxia and was found to have multiple intracranial lesions. Diagnostic workup was ultimately unrevealing, and his condition improved after a course of steroids and antibiotics. Unfortunately, symptoms returned 3 months later. MRI of the brain revealed progression of his intracranial lesions. This case highlights a diagnostic approach and general management strategy for patients presenting with undifferentiated intracranial pathology. A final diagnosis is ultimately reached and raises further discussion.

Cyanomethyl Vinyl Ethers Against Naegleria fowleri.

Naegleria fowleri is a pathogenic amoeba that causes a fulminant and rapidly progressive disease affecting the central nervous system called primary amoebic meningoencephalitis (PAM). Moreover, the disease is fatal in more than 97% of the reported cases, mostly affecting children and young people after practicing aquatic activities in nontreated fresh and warm water bodies contaminated with these amoebae. Currently, the treatment of primary amoebic meningoencephalitis is based on a combination of different antibiotics and antifungals, which are not entirely effective and lead to numerous side effects. In the recent years, research against PAM is focused on the search of novel, less toxic, and fully effective antiamoebic agents. Previous studies have reported the activity of cyano-substituted molecules in different protozoa. Therefore, the activity of 46 novel synthetic cyanomethyl vinyl ethers (QOET-51 to QOET-96) against two type strains of N. fowleri (ATCC 30808 and ATCC 30215) was determined. The data showed that QOET-51, QOET-59, QOET-64, QOET-67, QOET-72, QOET-77, and QOET-79 were the most active molecules. In fact, the selectivity index (CC50/IC50) was sixfold higher when compared to the activities of the drugs of reference. In addition, the mechanism of action of these compounds was studied, with the aim to demonstrate the induction of a programmed cell death process in N. fowleri.

Amebic encephalitis and meningoencephalitis: an update on epidemiology, diagnostic methods, and treatment.

PURPOSE OF REVIEW: Free-living amebae (FLA) including Naegleria fowleri , Balamuthia mandrillaris , and Acanthamoeba species can cause rare, yet severe infections that are nearly always fatal. This review describes recent developments in epidemiology, diagnosis, and treatment of amebic meningoencephalitis. RECENT FINDINGS: Despite similarities among the three pathogenic FLA, there are notable variations in disease presentations, routes of transmission, populations at risk, and outcomes for each. Recently, molecular diagnostic tools have been used to diagnose a greater number of FLA infections. Treatment regimens for FLA have historically relied on survivor reports; more data is needed about novel treatments, including nitroxoline. SUMMARY: Research to identify new drugs and guide treatment regimens for amebic meningoencephalitis is lacking. However, improved diagnostic capabilities may lead to earlier diagnoses, allowing earlier treatment initiation and improved outcomes. Public health practitioners should continue to prioritize increasing awareness and providing education to clinicians, laboratorians, and the public about amebic infections.

The 4-Aminomethylphenoxy-Benzoxaborole AN3057 as a Potential Treatment Option for Primary Amoebic Meningoencephalitis.

Primary amoebic meningoencephalitis is a rare but fatal central nervous system (CNS) disease caused by the "brain-eating amoeba" Naegleria fowleri. A major obstacle is the requirement for drugs with the ability to cross the blood-brain barrier, which are used in extremely high doses, cause severe side effects, and are usually ineffective. We discovered that the 4-aminomethylphenoxy-benzoxaborole AN3057 exhibits nanomolar potency against N. fowleri, and experimental treatment of infected mice significantly prolonged survival and demonstrated a 28% relapse-free cure rate.

In Silico Structural Analysis of Serine Carboxypeptidase Nf314, a Potential Drug Target in Naegleria fowleri Infections.

Naegleria fowleri, also known as the "brain-eating" amoeba, is a free-living protozoan that resides in freshwater bodies. This pathogenic amoeba infects humans as a casual event when swimming in contaminated water. Upon inhalation, N. fowleri invades the central nervous system and causes primary amoebic meningoencephalitis (PAM), a rapidly progressive and often fatal disease. Although PAM is considered rare, reducing its case fatality rate compels the search for pathogen-specific proteins with a structure-function relationship that favors their application as targets for discovering new or improved drugs against N. fowleri infections. Herein, we report a computational approach to study the structural features of Nf314 (a serine carboxypeptidase that is a virulence-related protein in N. fowleri infections) and assess its potential as a drug target, using bioinformatics tools and in silico molecular docking experiments. Our findings suggest that Nf314 has a ligand binding site suitable for the structure-based design of specific inhibitors. This study represents a further step toward postulating a reliable therapeutic target to treat PAM with drugs specifically aimed at blocking the pathogen proliferation by inhibiting protein function.

Successful Treatment of Primary Amoebic Meningoencephalitis Using a Novel Therapeutic Regimen Including Miltefosine and Voriconazole.

The genus Naegleria consists of free-living amoebae widely distributed worldwide in soil and freshwater habitats. Primary amoebic meningoencephalitis (PAM) is an uncommon and most likely fatal disease. The incubation period is approximately 7 days. The first symptoms are headache, nasal congestion, fever, vomiting, stiff neck within 3-4 days after the first symptoms, confusion, abnormal behavior, seizures, loss of balance and body control, coma, and death. We describe the case of a child who presented with PAM due to Naegleria sp., fully recovered from the infection without apparent sequels after treatment with a regimen that included miltefosine and voriconazole.

Primary amoebic meningoencephalitis in children- report of two cases from South India.

Primary Amoebic meningoencephalitis is a rare and fatal neuro-infection caused by free-living fresh-water amoeba Naegleria fowleri. It is a ubiquitous organism and the infection occurs usually via contact with warm water-bodies. The clinical presentation is often indistinguishable from acute bacterial meningitis and the diagnosis can be made by CSF wet smear examination if there is a high index of suspicion. The disease progresses rapidly compared to pyogenic meningitis and usually has a fatal outcome. Reports of two confirmed cases of primary amoebic meningoencephalitis in children from different centres in Kerala state of India are presented here. In spite of early diagnosis and treatment, both these patients demised. Primary amoebic meningoencephalitis should be considered in the differential diagnosis of acute meningitis, especially in patients with recent freshwater exposure. Implementation of chlorination of pools of water bodies, especially if re-opened for recreational purpose after prolonged periods of non-use, needs vigorous implementation.

Cyclolauranes as plausible chemical scaffold against Naegleria fowleri.

Primary amoebic meningoencephalitis (PAM) is a central nervous system (CNS) disease caused by Naegleria fowleri that mainly affects children and young adults with fatal consequences in most of the cases. Treatment protocols are based on the combination of different antimicrobial agents, nonetheless there is the need to develop new anti-Naegleria compounds with low toxicity and full effects compared to the currently used drug combination. The marine environment is a well-established source of bioactive natural products. In this work, we have focused on the structure of Laurencia cyclolaurane-type sesquiterpenes as potential chemical model against Naegleria species. The effects of debromolaurinterol (1) to induce PCD/apoptosis-like events in Naegleria fowleri have been evaluated, revealing that this compound induced reduction of ATP production showing a decrease of 99.98% in treated parasite cells. A SAR analysis have been supported with molecular modeling and analysis of the in silico ADME/Tox properties of the Laurencia sesquiterpenes debromolaurinterol (1), laurinterol (2) and allolaurinterol (3), which reinforce cyclolaurane metabolites as plausible molecular models to develop PAM treatments.

Differential Growth Rates and In Vitro Drug Susceptibility to Currently Used Drugs for Multiple Isolates of Naegleria fowleri.

The free-living amoeba Naegleria fowleri, which typically dwells within warm, freshwater environments, can opportunistically cause primary amoebic meningoencephalitis (PAM), a disease with a mortality rate of >97%. The lack of positive treatment outcomes for PAM has prompted the discovery and development of more effective therapeutics, yet most studies utilize only one or two clinical isolates. The inability to assess possible heterogenic responses to drugs among isolates from various geographical regions hinders progress in the discovery of more effective drugs. Here, we conducted drug efficacy and growth rate determinations for 11 different clinical isolates by applying a previously developed CellTiter-Glo 2.0 screening technique and flow cytometry. We found significant differences in the susceptibilities of these isolates to 7 of 8 drugs tested, all of which make up the cocktail that is recommended to physicians by the U.S. Centers for Disease Control and Prevention. We also discovered significant variances in growth rates among isolates, which draws attention to the differences among the amoeba isolates collected from different patients. Our results demonstrate the need for additional clinical isolates of various genotypes in drug assays and highlight the necessity for more targeted therapeutics with universal efficacy across N. fowleri isolates. Our data establish a needed baseline for drug susceptibility among clinical isolates and provide a segue for future combination therapy studies as well as research related to phenotypic or genetic differences that could shed light on mechanisms of action or predispositions to specific drugs. IMPORTANCE Naegleria fowleri, also known as the brain-eating amoeba, is ubiquitous in warm freshwater and is an opportunistic pathogen that causes primary amoebic meningoencephalitis. Although few cases are described each year, the disease has a case fatality rate of >97%. In most laboratory studies of this organism, only one or two well-adapted lab strains are used; therefore, there is a lack of data to discern if there are major differences in potency of currently used drugs for multiple strains and genotypes of the amoeba. In this study, we found significant differences in the susceptibilities of 11 N. fowleri isolates to 7 of the 8 drugs currently used to treat the disease. The data from this study provide a baseline of drug susceptibility among clinical isolates and suggest that new drugs should be tested on a larger number of isolates in the future.

A patient with granulomatous amoebic encephalitis caused by Balamuthia mandrillaris survived with two excisions and medication.

BACKGROUND: Granulomatous amoebic encephalitis (GAE) is a rare central nervous system infection caused by the Balamuthia mandrillaris or Acanthamoeba species. Diagnosis is challenging because of the non-specific clinical presentation, cerebrospinal fluid analysis, and radiological features. There is no effective treatment for GAE to date. CASE PRESENTATION: A 54-year-old male was admitted to hospital after experiencing acute onset of numbness and weakness on his left limb. Due to the initial consideration of intracranial tumor, surgical removal of the right parietal lesion was performed. However, the patient had a headache accompanied by diplopia, difficulty walking and a new lesion was found in the left occipital-parietal lobe two weeks after the first operation. High-throughput next-generation sequencing (NGS) detected the presence of high copy reads of the B. mandrillaris genome sequence in the patient's blood, cerebral spinal fluid (CSF), and brain tissue. Pathological investigation of the brain tissue showed granulomatous changes and amoebic trophozoite scattered around blood vessels under high magnification. The patient was re-operated due to developing progressive confusion caused by subfalcine herniation of the left cerebral hemisphere. The lesions of the right parietal lobe were obviously decreasing in size after the first surgery, and the lesions of the left occipital lobe and the sunfalcine herniation didn't ameliorate two months after the second surgery. The patient was transferred to local hospital for continuous treatment with sulfamethoxazole and azithromycin. After five months of the second surgery, the patient showed good recovery with mild headache. CONCLUSIONS: This is the first report of a patient with B. mandrillaris encephalitis initially confirmed by NGS and have experienced two excisions, responding favorably to the combination of surgeries and medications. Early surgical resection of intracranial lesions combined with drug treatment may offer the chance of a cure.