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How widespread is Acanthamoeba? They live in habitats you wouldn't expect!
Acanthamoeba is a common amoeba found in soil, freshwater, and a variety of habitats. Organisms of this genus have two main stages in their life cycle, the metabolically active vegetative stage and a dormant cyst stage that is resistant to environmental stress. Although in nature, Acanthamoeba species are generally free-living mycophagous bacteria, they can also become opportunistic pathogens that can cause serious and even fatal infections in humans and other animals.
Acanthamoeba species are extremely common in the environment, including soil, air, sewage, seawater, chlorinated swimming pools, household tap water, bottled water, and can be isolated in dental units, hospitals, air conditioning equipment and contact lens cases. out of them.
Acanthamoeba spp. are ubiquitous throughout the world and have been isolated from the skin, nose, throat, and intestines of humans and have even been found in plants and other mammals. This remarkable environmental adaptability makes them an indispensable part of the ecosystem.
The role of disease
Diseases caused by Acanthamoeba include keratitis and granulomatous amebic encephalitis (GAE). GAE usually occurs in immunocompromised patients when Acanthamoeba enters the body through an open wound and can spread to the brain. The host's immune response combined with proteases secreted by the amoeba causes swelling of the brain, killing about 95% of those infected.
Granulomatous amebic encephalitis (GAE) symptoms include headaches, seizures, and abnormal mental status, which worsen over time and ultimately lead to death. The potential cause of this disease is related to a variety of underlying diseases, including immunodeficiency, diabetes and malnutrition.
The process by which Acanthamoeba crosses the blood-brain barrier is not fully understood, but the subsequent tissue invasion and proinflammatory response can lead to neurological damage that can be fatal within days. Diagnosis and treatment of Acanthamoeba infections are currently difficult due to the rarity of the parasite and lack of knowledge.
Acanthamoebic Keratitis
When Acanthamoeba infects the eye, it can cause keratitis, which is most common in contact lens wearers, especially those who do not properly disinfect their lenses. All-purpose contact lens solutions are generally ineffective against Acanthamoeba, while hydrogen peroxide-based solutions are effective at disinfecting. Past cases of corneal infection have typically been treated with atropine and other drugs that have no antimicrobial effect. More recent studies have shown that the use of atropine interferes with specific receptors on the amoeba, leading to cell death.
In May 2007, Advanced Medical Optics voluntarily recalled its Complete Moisture Plus contact lens solution after the CDC found 21 people who may have been infected with Acanthamoeba after using the product.
As our knowledge of Acanthamoeba grows, the scientific community is working to find more effective treatment options. Although current treatments are somewhat effective, further research is needed to ensure that infections can be correctly and promptly diagnosed and treated.
Ecology and Physical Properties
A. castellanii can be found in high densities in a variety of soil ecosystems, where it feeds primarily on bacteria, but also on fungi and other protists. This species is capable of lytic bacteria and produces a variety of enzymes, providing an important contribution to the decomposition of soil organic matter, further promoting the microbial cycle.
Acanthamoeba is very important for studying cell biology, environmental biology and cell interactions. It is widely used as a model organism in many biological fields due to its high similarity to mammalian cells at the ultrastructural level.
In addition, analysis of the Acanthamoeba genome sequence revealed several genes involved in sexual reproduction, suggesting that Acanthamoeba may have some form of sexual reproduction capability, and that this capability may have existed early in the evolution of eukaryotes. A process.
Diversity and pathogenic potential
Acanthamoeba can be distinguished from other amoebas by morphological features, but it is relatively difficult to distinguish different species of Acanthamoeba based on morphology alone. Based on 18S rDNA sequence analysis, known Acanthamoeba strains can be grouped into 12 categories, involving many pathogenic species. Due to the environmental adaptability of Acanthamoeba, these organisms may become new pathogens.
These organisms may serve as environmental reservoirs for some human pathogens; many bacteria that cause disease in humans, such as Legionella and certain strains of E. coli, are able to infect and multiply in Acanthamoeba.
Acanthamoeba, which harbors a diverse bacterial endosymbiont, is considered a potential emerging human pathogen, making its further study particularly important.
In addition to biomedical research, studies on Acanthamoeba also provide information on neurodegenerative diseases. We can't help but ask, with such a wide environmental distribution, will Acanthamoeba become one of the most vexing challenges to human health in the future?
