Table 1. Clinical features of free-living amoebas.

CSF: cerebrospinal fluid; ICP: increased intracranial pressure; CNS: central nervous system

	Naegleria	Acanthamoeba	Balamuthia
Epidemiology	Lives on surfaces with rich biofilm. Risk factors: hematological malignancies, diabetes mellitus, prolonged use of antibiotics, immunosuppressive state. Approximately 150 cases have been reported worldwide. There is no sex predominance	Lives in temperatures above 30 degrees. Most common risk factor: participation in recreational water activities, approximately 300 cases have been reported worldwide. Males predominantly infected	Risk factors: immune-compromised Hispanic origin due to genetic susceptibility and environmental exposure. Approximately 109 cases reported worldwide. Male predominance
Median time from exposure to death	Eight days to several months	9.9 days	Weeks to years
Mortality	97%-98%	99%	95%
Clinical features	Headaches, neck stiffness, ataxia, irritability, photophobia, diplopia, hemiparesis, cranial nerve palsies, and increased ICP	Headaches, behavior abnormalities, neck stiffness, ataxia, irritability, photophobia, diplopia, high fever, meningeal signs, cranial nerve palsies, seizures, encephalitis, increased ICP, and keratitis	Headaches, behavior abnormalities, neck stiffness, ataxia, irritability, photophobia, diplopia, high fever, meningeal signs, cranial nerve palsies, seizures, encephalitis, increased ICP, and skin manifestations followed by a neurological compromise in weeks or months. The skin signs are: annular, non-ulcerated, infiltrative, asymptomatic plaque in the central face over the nose
Diagnosis	Microscopic findings reveal granulomas with multinucleated giant cells. Specific antibodies to different species of Acanthamoeba along with immunofluorescent staining can also be used.	CSF examination by the phase-contrast microscope is beneficial for ameba visualization of Giemsa or trichrome stains help to define morphology features	Recognition of the cutaneous and CNS findings. Visualization of the parasite is required for definitive diagnosis and is acquired by biopsy
Imaging	On CT/MRI, both enhancing and non-enhancing lesions can be seen. There are also multifocal areas of signal intensity or discrete lesions that may be seen,	CT scan and MRI findings are nonspecific. However, brain edema, hydrocephalus, basilar meningeal enhancement, and infarctions are described. These lesions are found on the frontal and temporal lobes, cerebellum, and spinal cord	Multiple lesions from small and solid to large and nodular lesions with ring enhancement surrounding vasogenic edema and regional mass effect may be present as intralesional hemorrhage, lesions can compromise both white and gray matter.
CFS Findings	Glucose: Low/Protein: High/CSF pressure: increased, Cells: pleocytosis with abundant lymphocytes and polymorphonuclear leukocytes	Glucose: Low/Protein Hiigh CSF pressure: increased/Cells: pleocytosis with abundant lymphocytes and polymorphonuclear leukocytes. Also red cells	Glucose: Normal to low/Protein: Normal to elevated/CSF pressure: Increased/cells: pleocytosis with abundant lymphocytes and polymorphonuclear leukocytes
Empiric Treatment	Initial dose of amphotericin B (IV) for three days, followed by amphotericin B (IV) with a smaller quantity for 14 days. Then, a regimen of azithromycin (IV/PO), rifampin (IV/PO), miltefosine, (IV/PO and dexamethasone (IV)	Pentamidine (PO), Sulfadiazine (PO), Flucytosine (PO), Fluconazole (PO or IV), miltefosine (PO), and azithromycin (PO). The duration of the treatment has not been established	Optimal treatment is uncertain