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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.
Naegleriasis 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.
Meningoencephalitis, also known as herpes meningoencephalitis, is a medical condition that simultaneously resembles both meningitis, which is an infection or inflammation of the meninges, and encephalitis, which is an infection or inflammation of the brain tissue.
Acanthamoeba keratitis (AK) is a rare disease in which amoebae of the genus Acanthamoeba invade the clear portion of the front (cornea) of the eye. It affects roughly 100 people in the United States each year. Acanthamoeba are protozoa found nearly ubiquitously in soil and water and can cause infections of the skin, eyes, and central nervous system.
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, usually 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.
Miltefosine, sold under the trade name Impavido among others, is a medication mainly used to treat leishmaniasis and free-living amoeba infections such as Naegleria fowleri and Balamuthia mandrillaris. This includes the three forms of leishmaniasis: cutaneous, visceral and mucosal. It may be used with liposomal amphotericin B or paromomycin. It is taken by mouth.
The term "brain-eating amoeba" has been used to refer to several microorganisms:
Human parasites include various protozoa and worms.
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Sappinia diploidea is a free-living amoeba species.
Amoebic brain abscess is an affliction caused by the anaerobic parasitic protist Entamoeba histolytica. It is extremely rare; the first case being reported in 1849. Brain abscesses resulting from Entamoeba histolytica are difficult to diagnose and very few case reports suggest complete recovery even after the administration of appropriate treatment regimen.
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.
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.
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.
Naegleria fowleri, colloquially known as the "brain-eating amoeba", is a species of the genus Naegleria. It belongs to the phylum Percolozoa and is technically classified as a shape-shifting 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
- ↑ Sarica, F. B.; Tufan, K.; Cekinmez, M.; Erdoğan, B.; Altinörs, M. N. (2009). "A rare but fatal case of granulomatous amebic encephalitis with brain abscess: the first case reported from Turkey". Turkish Neurosurgery. 19 (3): 256–259. PMID 19621290.
- ↑ Da Rocha-Azevedo, B.; Tanowitz, H.; Marciano-Cabral, F. (2009). "Diagnosis of infections caused by pathogenic free-living amoebae". Interdisciplinary Perspectives on Infectious Diseases. 2009: 1–14. doi: 10.1155/2009/251406 . PMC 2719787 . PMID 19657454.
- ↑ Visvesvara, G.; Moura, H.; Schuster, F. (2007). "Pathogenic and opportunistic free-living amoebae: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea". FEMS Immunology and Medical Microbiology. 50 (1): 1–26. doi:10.1111/j.1574-695X.2007.00232.x. PMID 17428307.
- ↑ Maruyama, S.; Matsuzaki, M.; Misawa, K.; Nozaki, H. (2009). "Cyanobacterial contribution to the genomes of the plastid-lacking protists". BMC Evolutionary Biology. 9: 197. doi: 10.1186/1471-2148-9-197 . PMC 3087521 . PMID 19664294.