Balamuthia mandrillaris is a rare and difficult-to-diagnose infection with high mortality. We present the case of an immunocompetent toddler presenting with central nervous system (CNS) vasculitis. He was initially diagnosed with Takayasu arteritis and had an initial period of improvement following immunosuppressive therapy. Subsequently, he had rapid decompensation with diffuse intracranial lesions progressing to severe neurological injury and compassionate extubation. Metagenomic sequencing of the CSF and pathology and PCR from brain biopsy were positive for B. mandrillaris To our knowledge, this is the first case of Balamuthia presenting as a mixed vessel CNS vasculitis and highlights the importance of consideration of this infection in cases of vasculitis, particularly in mixed vessel disease. It further demonstrates the potential use of newer diagnostics, namely CSF metagenomic testing and amoeba PCR, in earlier diagnosis and treatment.

Amebic liver abscess (ALA), caused by Entamoeba histolytica, is the most common extraintestinal manifestation of amebiasis. However, in contemporary clinical practice, diagnosis increasingly relies on serology and polymerase chain reaction (PCR), whereas direct microscopic identification of motile trophozoites in aspirated specimens has become rarely documented. Furthermore, optimal management necessitates complete anti-amebic therapy covering both invasive tissue stages and luminal intestinal colonization to prevent relapse. Here, we report a case of a 25-year-old male with a history of splenectomy and pulmonary tuberculosis, presenting with fever, right upper quadrant pain, and cough. Imaging revealed a right hepatic lobe abscess. While abscess and blood cultures remained sterile, sputum culture grew E. coli. Fresh microscopic examination of the aspirate readily demonstrated motile, erythrophagocytic trophozoites, subsequently confirmed as E. histolytica by sequencing. Although the patient showed initial clinical improvement with metronidazole, he later developed severe bleeding and ulceration of the ascending colon, ultimately requiring partial colectomy. This case underscores the enduring diagnostic value of conventional wet-mount microscopy in the molecular era, offering a rapid and cost-effective tool. Critically, it also highlights a key therapeutic principle ALA treated with a tissue-active agent must be followed by a luminal agent to eradicate intestinal carriage. Failure to do so risks persistent colonic disease, severe complications, or treatment failure, as observed in this patient.

Granulomatous amoebic encephalitis (GAE) is a rare but highly fatal central nervous system infection caused primarily by Acanthamoeba spp. and Balamuthia mandrillaris. Delayed diagnosis and the absence of standardized treatment protocols contribute to mortality exceeding 90%. This review summarizes current knowledge regarding GAE pathogenesis, diagnosis, therapeutic challenges, and emerging treatment strategies. The pathogenesis involves amoebic adhesion, secretion of proteases and phospholipases, host inflammatory responses, and blood-brain barrier disruption. Recent advances in molecular diagnostics improve early pathogen detection, while drug repurposing, nanotechnology-based delivery systems, and cyst-targeted approaches represent promising therapeutic strategies. Nevertheless, treatment remains challenging because of poor blood-brain barrier penetration, cyst-associated resistance, and limited clinical evidence. Continued integration of molecular diagnostics, mechanistic studies, translational research, and multicentre clinical investigations is essential for improving outcomes in this devastating disease.

Chloroquine is used for the treatment of uncomplicated malaria and extra-intestinal amebiasis. Malaria is caused by infection of Plasmodium parasites. Chloroquine is active against the erythrocytic forms of susceptible strains of Plasmodium falciparum (P. falciparum), Plasmodium malariae (P. malariae), Plasmodium ovale (P. ovale), and Plasmodium Vivax (P. vivax). Chloroquine is not active against the gametocytes and the exoerythrocytic forms including the hypnozoite stage (P. vivax and P. ovale) of the Plasmodium parasites. Additionally, resistance to chloroquine and hydroxychloroquine has been reported in Plasmodium species, thus chloroquine therapy is not indicated if the infection arose in a region with known resistance. Chloroquine is used in first-line treatment of P. vivax malaria with primaquine. Studies have indicated chloroquine is effective against the trophozoites of Entamoeba histolytica (E. histolytica), which causes amebic dysentery, or amebiasis. (1) Chloroquine also has off-label uses for treatment of rheumatic diseases and has been investigated as a potential antiviral therapy as well as an adjuvant chemotherapy for several types of cancer. (2, 3, 4, 5) Chloroquine accumulates in cellular acidic compartments such as the parasitic food vacuole and mammalian lysosomes, leading to alkalinization of these structures. This change in pH can impair the action of enzymes responsible for the formation of hemozoin by the parasite from ingestion of the host’s hemoglobin; this reaction occurs in the parasitic vacuole (6). Thus, chloroquine targets the blood-stage of the malaria parasites but cannot eliminate dormant hypnozoites and must be administered with a drug that targets the dormant parasitic form (1). Chloroquine, developed in the 1940s, has been superseded as the first-line recommended antimalarial therapy by both the US Centers for Disease Control (CDC) and World Health Organization (WHO), with the exceptions of during the first trimester of pregnancy or for malarial prophylaxis of a pregnant individual who is also deficient for glucose-6-phosphate dehydrogenase (G6PD) (7, 8). Among antimalarial medications, chloroquine is less likely than other medicines to cause hemolysis in G6PD-deficient individuals; however, the FDA-approved drug label states there is still a risk of hemolysis (Table 1) (1). In contrast, the Clinical Pharmacogenetics Implementation Consortium (CPIC) performed a systematic review of the available clinical literature and found low-to-no risk of acute hemolytic anemia for individuals with G6PD deficiency who take hydroxychloroquine or chloroquine (9) (Table 2). It should be noted that G6PD deficiency has a range of severity; CPIC advises caution for all medications when used by an individual with a severe G6PD deficiency with chronic non-spherocytic hemolytic anemia (CNSHA).

Therapeutic failure in Acanthamoeba Keratitis (AK) is largely driven by the high resistance of cysts to antimicrobial agents. However, the development of effective cysticidal drugs is hindered by the lack of standardized in vitro encystation protocols. Inconsistencies in induction methods can produce immature cells that lack the structural defenses of mature clinical walls, potentially leading to false-positive results in drug screening. This study aims to evaluate the impact of cyst maturity on drug resistance assays by systematically comparing two common liquid media-glucose-supplemented PBS (PBSEB) and alkaline encystation buffer (EB2)-within Acanthamoeba Genotype T4 backgrounds. We assessed morphological transitions, transcriptional profiles (EMSP, ATG8, and CS-I), ultrastructure (TEM), and functional resistance to sodium dodecyl sulfate (SDS) and chlorhexidine gluconate (CHG) using environmental reference and clinical isolates, including the stress-tolerant NCKU_D strain. Although both media induced morphological rounding and upregulated the autophagy marker ATG8, functional and molecular assays revealed distinct developmental outcomes. PBSEB-treated cells failed to significantly upregulate the critical early serine proteinase EMSP and exhibited insufficient CS-I expression, remaining highly susceptible to SDS lysis and lacking intact walls under TEM. Conversely, EB2 triggered a robust 11.8-fold increase in EMSP, yielding structurally mature, SDS-resistant cysts. Importantly, functional assays demonstrated that EB2-induced cysts exhibited significantly higher chemical resistance to CHG than the PBSEB group at 48 h, with this resistance advantage further widening by 72 h of induction. Based on these distinct profiles, we suggest that while PBSEB serves as a useful model for investigating cell detachment kinetics and early autophagic pathways, the EB2 protocol is more suitable for evaluating downstream therapeutic efficacy and product safety where functional, double-walled resistance is required to avoid false-positive outcomes in Genotype T4 drug screening.

Neuroinvasive free-living amoebae (FLA), particularly Naegleria fowleri and Acanthamoeba spp., are responsible for rare but devastating infections of the central nervous system (CNS). Approximately 480 cases of primary amoebic meningoencephalitis (PAM) and fewer than 200 well-documented cases of Acanthamoeba-associated granulomatous amoebic encephalitis (GAE) have been reported worldwide. Mortality rates frequently exceed 90%. PAM typically develops following exposure to warm freshwater contaminated with N. fowleri and progresses rapidly in otherwise healthy individuals. In contrast, GAE usually follows a more indolent course and occurs predominantly in immunocompromised hosts. Despite their distinct clinical courses, both infections are characterized by CNS invasion, amoeba-mediated tissue destruction, blood-brain barrier (BBB) disruption, and host inflammatory responses. These processes drive neuroinflammation, neuronal injury, and neurological deterioration. Early diagnosis remains challenging because clinical manifestations are nonspecific and disease progression can be either fulminant or initially subtle. Therapeutic management is hindered by poor CNS drug penetration, limited efficacy of currently available therapies, treatment-related toxicity, and the absence of standardized treatment protocols or controlled clinical trials. This narrative review critically synthesizes current evidence on CNS invasion, neuroinflammation, neuropathology, diagnostic challenges, and therapeutic strategies in neuroinvasive FLA infections. It also highlights key translational priorities, including earlier diagnosis, standardized treatment protocols, stronger clinical evidence, and improved CNS-targeted drug delivery.

Balamuthia mandrillaris is a highly lethal free-living ameba that primarily affects the skin and central nervous system, manifesting clinically as chronic granulomatous lesions and granulomatous encephalitis. Once the central nervous system is involved, the mortality rate exceeds 90%. No standardized treatment regimen has yet been established. In this review, we summarized 66 cases reported from China. The median patient age was 36 years (range 10 months-77 years); 62.12% patients were male and 37.88% female. Fifty-five (83.33%) patients were immunocompetent. For 42 (63.64%) patients, initial symptoms were cutaneous manifestations; of those, central nervous system involvement subsequently developed in 25 (59.52%) patients. Twenty-four (36.36%) patients were hospitalized initially with encephalitis. Among the 63 patients with a known outcome, 43 (68.25%) succumbed to infection. For patients with cutaneous-only disease, the survival rate was 93.75%, whereas once the central nervous system was affected, mortality reached 96.00%.

We report a systematic case review of antemortem neurosurgical resections and biopsies and outcomes including new lesions after procedure and survival in Balamuthia mandrillaris granulomatous amebic encephalitis. The investigation was prompted by a 5-year-old patient in the southwestern United States who was treated with nitroxoline, the 2021 Centers for Disease Control and Prevention regimen, and underwent 2 resections; initial resection site recurrence and a new lesion after resection prompted the question whether complete resection versus biopsy is associated with better outcomes. We conducted a literature review and found no substantial difference between neurosurgical resection versus biopsy-only groups. Limitations include case review, number of cases, and incomplete data available. Additional analyses comparing neurosurgical outcomes with outcomes of those diagnosed via blood or cerebrospinal fluid and metagenomic next-generation sequencing might provide more definitive answers. This case and systematic review provide evidence that treatment with nitroxoline and neurosurgical resection could contribute to survival in Balamuthia encephalitis case-patients.

Entamoeba histolytica is a protozoan parasite that causes amebic colitis, a leading cause of severe diarrheal disease worldwide, and amebic liver abscess, the most common extraintestinal manifestation of infection. The disease burden is highest in resource-limited settings but remains clinically important in travelers and men who have sex with men in non-endemic regions. Although most infections are asymptomatic, severe and fulminant disease is associated with high mortality, particularly among individuals exposed to corticosteroids or other forms of immunosuppression. The increasing use of molecular diagnostic tools has improved understanding of the epidemiology of E. histolytica and enabled distinction from morphologically identical but nonpathogenic Entamoeba species; however, these diagnostics remain underutilized in many endemic settings due to cost and infrastructure limitations. Treatment options remain limited, with nitroimidazoles constituting the only drug class available for symptomatic invasive disease, leaving few alternatives for patients who cannot tolerate therapy or in the event of emerging resistance. Despite advances in understanding parasite pathogenesis and the application of high-throughput technologies, no licensed vaccine exists, and progress toward vaccine development has been minimal. These persistent gaps highlight the need to reprioritize amebiasis as a neglected tropical disease and to accelerate investment in diagnostics, therapeutics, and preventive strategies.

The development of effective vaccines against Entamoeba histolytica remains a major challenge, particularly for preventing amoebic liver abscess (ALA). In this study, carbon nanotubes (CNTs) were evaluated as nanocarriers through bioconjugation with L220-derived peptides (PL220-CNTs). CNTs were synthesized, purified, and characterized, confirming successful bioconjugation (42%). In vitro, PL220-CNTs exhibited negligible cytotoxicity in J774 macrophages and induced morphological changes characterized by cytoplasmic prolongations and phagosome-like structures. In vivo, subcutaneous immunization of hamsters induced antigen-specific responses, including splenocyte proliferation and increased IL-17A production, suggesting the participation of an IL-17A-associated immune response. Notably, animals immunized with PL220-CNTs exhibited limited antibody production against L220-derived peptides, suggesting a predominantly cellular immune response. PL220-CNT immunization conferred complete protection against ALA following intrahepatic challenge, whereas L220 alone provided partial protection. Histological analyses revealed preservation of hepatic architecture and reduced inflammatory damage in PL220-CNT-immunized animals. Overall, these findings support the potential of bioconjugated CNTs as immunomodulatory nanoplatforms for vaccine development against amoebiasis and other infectious diseases.

Intestinal protists represent an underappreciated yet functionally significant component of the human gut microbiome. Historically dismissed as parasites or transient contaminants, many of these microbial eukaryotes, particularly Entamoeba spp., are now recognized as integral to gut ecosystem function and host immune homeostasis. This review examines the complex roles of Entamoeba spp. in the mammalian gut, positioning them as dynamic microbiome "landscapers" that influence host-pathogen interactions, immune tone, and microbial diversity. We explore the evolutionary adaptation of Entamoeba to the gut's anaerobic and immunologically active environment, highlighting both pathogenic (E. histolytica) and non-pathogenic species (E. dispar, E. coli) and their distinct immunomodulatory strategies. Special attention is given to the host immune responses shaped by E. histolytica, including inflammasome activation, macrophage polarization, and suppression of protective type-2 responses. The review also details Entamoeba's interactions with the gut microbiota, emphasizing their capacity for selective bacterial predation, disruption or enhancement of microbial community structure, and synergistic or antagonistic relationships with commensals and pathogens alike. Methodological challenges in protist detection, genome annotation, and cultivation are discussed, alongside promising advances in sequencing, host DNA depletion, and animal modeling. Taken together, current evidence reframes Entamoeba spp. not as mere pathogens but as key ecological players whose presence can signal resilience or susceptibility within the gut ecosystem. Understanding the context-dependent functions of intestinal protists may offer new insights into microbial therapeutics, immune modulation, and disease prevention strategies.