B. mandrillaris, an amoeba.
Swimming in fresh water and soil. Not swimmin in soil; it is found in soil.
It has been spread in transplanted organs(Pubmed).
Meningoencephalitis (PubMed). Can be indolent with a granulomatous encephalitis and can mimic brain tumor.
Diagnosis difficult premortem because amebas are difficult to identify under the microscope, even with commonly used stains.
"Survivors of Balamuthia infection were treated with a combination of antimicrobials, including pentamadine isothionate, 5-fluorocytosine (flucytosine), fluconazole, sulfadiazine, and a macrolide antibiotic (azithromycin or clarithromycin), with or without a phenothiazine compound (PubMed)."
But usually fatal.
See McCoy, Bones.