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Acanthamoeba is a genus of amoebae that are commonly recovered from soil, fresh water, and other habitats. The genus Acanthamoeba has two stages in its life cycle, the metabolically active trophozoite stage and a dormant, stress-resistant cyst stage. In nature, Acanthamoeba species are generally free-living bacterivores. However, they are also opportunistic pathogens able to cause serious and sometimes fatal infections in humans and other animals.
Free-living amoebae in the Amoebozoa group are important causes of disease in humans and animals.
Naegleriasis, also known as primary amoebic meningoencephalitis (PAM), is an almost invariably fatal infection of the brain by the free-living unicellular eukaryote Naegleria fowleri. Symptoms are meningitis-like and include headache, fever, nausea, vomiting, a stiff neck, confusion, hallucinations and seizures. Symptoms progress rapidly over around five days, and death usually results within one to two weeks of symptoms.
Naegleria is a free living amoebae protist genus consisting of 47 described species often found in warm aquatic environments as well as soil habitats worldwide. It has three life cycle forms: the amoeboid stage, the cyst stage, and the flagellated stage, and has been routinely studied for its ease in change from amoeboid to flagellated stages. The Naegleria genera became famous when Naegleria fowleri, a human pathogenic strain and the causative agent of primary amoebic meningoencephalitis (PAM), was discovered in 1965. Most species in the genus, however, are nonpathogenic, meaning they do not cause disease.
Lobosa is a taxonomic group of amoebae in the phylum Amoebozoa. Most lobosans possess broad, bluntly rounded pseudopods, although one genus in the group, the recently discovered Sapocribrum, has slender and threadlike (filose) pseudopodia. In current classification schemes, Lobosa is a subphylum, composed mainly of amoebae that have lobose pseudopods but lack cilia or flagella.
The tectofilosids are a group of filose amoebae with shells. These are composed of organic materials and sometimes collected debris, in contrast to the euglyphids, which produce shells from siliceous scales. The shell usually has a single opening, but in Amphitrema and a few other genera it has two on opposite ends. The cell itself occupies most of the shell. They are most often found on marsh plants such as Sphagnum.
Discosea is a class of Amoebozoa, consisting of naked amoebae with a flattened, discoid body shape. Members of the group do not produce tubular or subcylindrical pseudopodia, like amoebae of the class Tubulinea. When a discosean is in motion, a transparent layer called hyaloplasm forms at the leading edge of the cell. In some discoseans, short "subpseudopodia" may be extended from this hyaloplasm, but the granular contents of the cell do not flow into these, as in true pseudopodia. Discosean amoebae lack hard shells, but some, like Cochliopodium and Korotnevella secrete intricate organic scales which may cover the upper (dorsal) surface of the cell. No species have flagella or flagellated stages of life.
Balamuthia mandrillaris is a free-living amoeba that causes the rare but deadly neurological condition granulomatous amoebic encephalitis (GAE). B. mandrillaris is a soil-dwelling amoeba and was first discovered in 1986 in the brain of a mandrill that died in the San Diego Wild Animal Park.
Granulomatous amoebic encephalitis (GAE) is a rare, often fatal, subacute-to-chronic central nervous system disease caused by certain species of free-living amoebae of the genera Acanthamoeba, Balamuthia and Sappinia. The term is most commonly used with Acanthamoeba. In more modern references, the term "balamuthia amoebic encephalitis" (BAE) is commonly used when Balamuthia mandrillaris is the cause.
The family Acrasidae is a family of slime molds which belongs to the excavate group Percolozoa. The name element acrasio- comes from the Greek akrasia, meaning "acting against one's judgement". This group consists of cellular slime molds.
Sappinia is a genus of heterotrophic, lobose amoebae within the family Thecamoebidae. A defining feature of Sappinia, which separates it from its sister genus Thecamoeba, is the presence of two closely apposed nuclei with a central, flattened connection. Sappinia species have two life cycle stages: a trophozoite and a cyst. Up until 2015, only two species had been discovered, Sappinia pedata and Sappinia diploidea. Sequencing of the small subunit rRNA of a particular isolate from a sycamore tree revealed a new species, Sappinia platani.Sappinia species were once thought to be coprozoic, as the first strains were isolated from animal dung. More research has shown that they are typical free-living amoebae, and can be found worldwide in soil, plant litter, and standing decaying plants, as well as freshwater ponds. In 2001, the first and only case of human pathogenesis in Sappinia was confirmed. The patient was a non-immunocompromised 38-year-old male who presented signs of amoebic encephalitis and who patient made a full recovery after treatment with several antimicrobials. The CDC initially classified the causative agent as S. diploidea based on morphological characteristics, but in 2009, Qvarnstrom et al. used molecular data to confirm that the true causative agent was S. pedata.
Cutaneous amoebiasis, refers to a form of amoebiasis that presents primarily in the skin. It can be caused by Acanthamoeba or Entamoeba histolytica. When associated with Acanthamoeba, it is also known as "cutaneous acanthamoebiasis". Balamuthia mandrillaris can also cause cutaneous amoebiasis, but can prove fatal if the amoeba enters the bloodstream It is characterized by ulcers. Diagnosis of amebiasis cutis calls for high degree of clinical suspicion. This needs to be backed with demonstration of trophozoites from lesions. Unless an early diagnosis can be made such patients can develop significant morbidity.
Acanthamoebidae is a family of single-celled eukaryotes within the group Amoebozoa.
Thecamoebidae is an Amoebozoa family.
Balamuthia infection is a cutaneous condition resulting from Balamuthia that may result in various skin lesions.
Sappinia pedata is a species of Amoebozoa. Sappinia is a free-living amoeba, found in the environment. This organism can cause granulomatous amoebic encephalitis (GAE), however, only one case of GAE due to S. pedata infection has ever been reported, and the patient survived without any long-term consequences.
Sappinia amoebic encephalitis (SAE) is the name for amoebic encephalitis caused by species of Sappinia.
An amoeba, often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopods. Amoebae do not form a single taxonomic group; instead, they are found in every major lineage of eukaryotic organisms. Amoeboid cells occur not only among the protozoa, but also in fungi, algae, and animals.
Amphitrema is a genus of testate amoeba in the family Amphitremidae. The genus is commonly found in Sphagnum-dominated peatlands. All species of this genus are mixotrophic and harbor unicellular algae belonging to genus Chlorella.
Naegleria fowleri, also known as the brain-eating amoeba, is a species of the genus Naegleria. It belongs to the phylum Percolozoa and is technically classified as an amoeboflagellate excavate, rather than a true amoeba. This free-living microorganism primarily feeds on bacteria but can become pathogenic in humans, causing an extremely rare, sudden, severe, and usually fatal brain infection known as naegleriasis or primary amoebic meningoencephalitis (PAM).
References
- ↑ Visvesvara GS; Moura H; Schuster FL (June 2007). "Pathogenic and opportunistic free-living amoebae: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea". FEMS Immunol. Med. Microbiol. 50 (1): 1–26. doi:10.1111/j.1574-695X.2007.00232.x. PMID 17428307.
- ↑ Brown MW; Spiegel FW; Silberman JD (2007). "Amoeba at attention: phylogenetic affinity of Sappinia pedata". J. Eukaryot. Microbiol. 54 (6): 511–9. doi:10.1111/j.1550-7408.2007.00292.x. PMID 18070328. S2CID 45094015.
- 1 2 Brown; J.D. Silberman; F.W. Spiegel (2007). "Amoeba at attention: phylogenetic affinity of Sappinia pedata". J Eukaryot Microbiol. 54 (6): 511–9. doi:10.1111/j.1550-7408.2007.00292.x. PMID 18070328. S2CID 45094015 . Retrieved 8 December 2011.
- ↑ "Acanthamoeba: Overview - eMedicine" . Retrieved 2009-01-11.
- ↑ Gelman BB, Rauf SJ, Nader R, et al. (May 2001). "Amoebic encephalitis due to Sappinia diploidea". JAMA. 285 (19): 2450–1. doi:10.1001/jama.285.19.2450. PMID 11368696.
- ↑ Wylezich, C.; Walochnik, J.; Michel, R. (2009). "High genetic diversity of Sappinia-like strains (Amoebozoa, Thecamoebidae) revealed by SSU rRNA investigations". Parasitology Research. 105 (3): 869–873. doi:10.1007/s00436-009-1482-1. PMID 19495795. S2CID 28942657.
- ↑ Gelman, B.B. "Parasites-Sappinia". Amoebic encephalitis due to Sappinia diploidea. JAMA, 2001. Retrieved 8 December 2011.
- ↑ Gelman BB, Popov V, Chaljub G, et al. (October 2003). "Neuropathological and ultrastructural features of amebic encephalitis caused by Sappinia diploidea". J. Neuropathol. Exp. Neurol. 62 (10): 990–8. doi:10.1093/jnen/62.10.990. PMID 14575235.
- ↑ Marciano‐Cabral F (2009). "Free‐Living Amoebae as Agents of Human Infection". J Infect Dis. 199 (8): 1104–1106. doi: 10.1086/597474 . PMID 19302009.
