Biomedical Engineering Reference
In-Depth Information
Sappinia is a genus of free-living organisms, within Class Lobosea. There
are two species capable of producing meningoencephalitis: Sappinia diploi-
dea and its nearly identical species, Sappinia pedata. Sappinia species can
be found in trophozoite form (i.e., feeding amoeboid forms) and cyst form.
The trophozoites are recognized by their two closely apposed nuclei, with a
central flattening. Sappinia encephalitis may occur in immune-competent
individuals. Only a few cases have been reported [83].
Genus Acanthamoeba and Genus Balamuthia are members of Class
Acanthamoebidae. There are a variety of Acanthamoeba species that cause a
similar set of human diseases. These include: Acanthamoeba rhysoides,
Acanthamoeba polyphaga, Acanthamoeba palestinensis, Acanthamoeba
hatchetti, Acanthamoeba culbertsoni, Acanthamoeba castellani, and
Acanthamoeba astronyxis. These similar species are herein aggregated under
the name Acanthamoeba species.
The Acanthamoeba are ubiquitous and are found in the domestic water
supply. Acanthamoeba species cause three distinctive clinical diseases: granu-
lomatous amoebic encephalitis, amoebic keratitis, and cutaneous acanthamoe-
biasis [83]. Though many people are exposed to Acanthamoeba species, few
develop disease. Granulomatous encaphalitis and cutaneous acanthamoebiasis
occur most often in people with immune deficiencies. Trophozoites and cyst
forms can be observed in infected tissues. The trophozoite form may be con-
fused histologically with macrophages. Trophozoites have a single nucleus
with a single large nucleolus. The cyst form can be visualized with a variety
of histologic stains [83]. Acanthamoebic granulomatous encephalitis is a very
rare disease, with a few hundred cases reported, worldwide. Only a few cases
of cutaneous acanthamoebiasis have been reported.
Acanthamoebic keratitis can occur in immune-competent individuals.
It occurs most often in contact lens users, presumably from washing the lens
in water containing the Acanthamoeba species.
The other pathogenic genus within Class Acanthamoebidae is Balamuthia. The
only known pathogenic species of this genus is Balamuthia mandrillaris,which
causes a granulomatous encephalitis, much like that caused by Acanthamoeba
species. The organism is found in soil, and possibly water. Like the other
pathogenic members of Class Amoebozoa, it occurs in two forms: trophozoite
and cyst. In tissue sections, Balamuthia mandrillaris is indistinguishable from
Acanthamoeba species by standard microscopic examination. Cases of
Balamuthia encephalitis are extremely rare, with only a few cases reported in
the USA each year, primarily in immune-compromised patients.
Amoebozoa
Conosa
Archamoebae
Pelobiontida
*Entamoeba
