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Kot, K. Acanthamoeba spp.. Encyclopedia. Available online: https://encyclopedia.pub/entry/8078 (accessed on 26 April 2024).
Kot K. Acanthamoeba spp.. Encyclopedia. Available at: https://encyclopedia.pub/entry/8078. Accessed April 26, 2024.
Kot, Karolina. "Acanthamoeba spp." Encyclopedia, https://encyclopedia.pub/entry/8078 (accessed April 26, 2024).
Kot, K. (2021, March 17). Acanthamoeba spp.. In Encyclopedia. https://encyclopedia.pub/entry/8078
Kot, Karolina. "Acanthamoeba spp.." Encyclopedia. Web. 17 March, 2021.
Acanthamoeba spp.
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This entry is adapted from the peer-reviewed paper 10.3390/ijms22031261

Acanthamoeba spp. are free-living amoebas, which are widely distributed in soil, water, and air. They are capable of causing granulomatous amebic encephalitis, Acanthamoeba pneumonia, Acanthamoeba keratitis, and disseminated acanthamoebiasis.

Acanthamoeba spp. free-living amoebas

1. Introduction

Acanthamoeba spp. are free-living amoebas (FLA) widely distributed in the environment, including soil, water, and air [1]. They are capable of causing cerebral (granulomatous amebic encephalitis, GAE) and extracerebral (Acanthamoeba keratitis, AK; Acanthamoeba pneumonia, AP; cutaneous acanthamoebiasis and disseminated acanthamoebiasis) life-threatening infections among humans [2]. Acanthamoeba spp. exist as an active (trophozoite) and dormant (cyst) forms. The cysts can abide and survive in various environments for years and transform into trophozoites under favorable environmental conditions [3].

Cerebral and extracerebral infections caused by Acanthamoeba spp. occur mostly among immunocompromised individuals, including HIV positive, organ transplant recipients, patients with chronic diseases, and those who undergo immunosuppressive therapy. Acanthamoebiasis has also been observed in immunocompetent individuals [4][5]. Despite low occurrence worldwide, the mortality rate of Acanthamoeba spp. infections is very high. The pathogenesis of acanthamoebiasis is not fully understood. Acanthamoeba spp. may invade through different ways, such as the respiratory tract or breaks in the skin, resulting in hematogenous dissemination to the brain [6]. Acanthamoeba spp. infections cases are often underdiagnosed and hence strong clinical suspicion along with laboratory technical expertise is required for early diagnosis and therapeutic intervention [7].

2. Biology of Acanthamoeba spp.

Acanthamoeba spp. exist in two distinct forms: an actively feeding and dividing trophozoite (15–45 μm) and a dormant cyst stage (12–25 μm) [8]. Both stages are infective to humans. Trophozoites of Acanthamoeba spp. actively feed on bacteria, yeast, algae and small organic particles. Cysts are formed after exposure to unfavorable environmental conditions, including changes in humidity, temperature, or environmental pH [4]. Cysts are resistant to many chemical and physical factors, including UV radiation, osmotic pressure, disinfectants, and antiseptics [9][10]. They can survive in the environment for more than 20 years [11].

3. Genome of Acanthamoeba spp.

Acanthamoeba species are identified based on the analysis of the diagnostic fragment 3 (DF3) region of the ribosomal DNA gene, designated Acanthamoeba-specific amplimer S1 (ASA.S1) [12]. DF3 encodes the highly variable stem 29-1 of the nuclear small subunit 18S rRNA gene [13]. Acanthamoeba genotypes are distinguished by a 5% or greater sequence difference between isolates [14][15]. To date, 22 sequence types have been identified, designated T1 through T22 [16]. However, Booton et al. [17], examining the DF3 subregion of ASA.S1 in the samples of T3 and T4 isolates, observed several unique sequences within T3 and T4 isolates. These sequences were designated T3/1–T3/5 and T4/1–T4/10 [17]. Due to the fact that different laboratories applied redundant numerical labels to identify different sequences, Fuerst and Booton [16] suggested new subtypes for the T4 genotype, which have been labeled T4A–T4F and T4Neff. The authors also described different sequences within T3 (labeled T3/01–T3/13), T5 (labeled T5/01–T5/15), T11 (labeled T11/01–T11/14), and T15 (labeled T15/01–T15/11). Types T2 and T6 are the most closely related pair of sequence types within Acanthamoeba, and these two types are considered as a supergroup in which five subtypes are formed: T2, T2/6A, T2/6B, T2/6C and T6 [16].

Among all genotypes, T4 is the most frequently isolated from nature, and it includes many pathogenic strains that have been associated with neurological and pulmonary acanthamoebiasis. It is assumed that T4 is characterized by increased virulence and increased resistance to chemotherapeutic agents [18]. The genotypes T1, T2, T4, T5, T10, T11, and T12 are the factors of granulomatous amebic encephalitis [13][19], whereas T2, T4, T5, T16, and T18 may be the factors of Acanthamoeba pneumonia [20][21][22][23].

4. Occurrence of Acanthamoeba spp. in the Environment

Acanthamoeba spp. are free-living protozoa that are widely distributed in the environment. Trophozoites and cysts of Acanthamoeba spp. with varying degrees of pathogenicity were found in the water, soil, and air samples. They occur in the rivers, seas, ocean sediments, lakes, ponds, hot springs, water sewage, swimming pools, rainwater, and even in mineral and bottled water [5]. In recent years, Acanthamoeba spp. have been isolated from tap water in Lithuania and city water in Iran [24][25]. In Poland, Derda et al. [26] isolated Acanthamoeba spp. from fountains, and Górnik and Kuźna-Grygiel [27] found the presence of pathogenic Acanthamoeba strains in natural recreational tanks and indoor as well as outdoor swimming pools. Acanthamoeba spp. strains were also isolated from potting soil, dust, air conditioning, dental units and dialysis stations [28]. Besides, amoebas were isolated from vegetables, fruits, mushrooms, but also from biological materials, such as swabs from the nasal mucosa, throat, and purulent secretions from the ear [26]. In Nigeria, the colonization of nasal mucosa by Acanthamoeba spp. was found in 24% of the studied participants [29]. The ubiquity of Acanthamoeba spp. is confirmed by the fact that 80% of the human population has natural IgG antibodies against Acanthamoeba spp. [30].

References

  1. Lass, A.; Guerrero, M.; Li, X.; Karanis, G.; Ma, L.; Karanis, P. Detection of Acanthamoeba spp. in water samples collected from natural water reservoirs, sewages, and pharmaceutical factory drains using LAMP and PCR in China. Sci. Total Environ. 2017, 584–585, 489–494.
  2. Marciano-Cabral, F.; Cabral, G. Acanthamoeba spp. as agents of disease in humans. Clin. Microbiol. Rev. 2003, 16, 273–307.
  3. Juárez, M.M.; Tártara, L.I.; Cid, A.G.; Real, J.P.; Bermúdez, J.M.; Rajal, V.B.; Palma, S.D. Acanthamoeba in the eye, can the parasite hide even more? Latest developments on the disease. Cont. Lens. Anterior Eye 2018, 41, 245–251.
  4. Kot, K.; Łanocha-Arendarczyk, N.A.; Kosik-Bogacka, D.I. Amoebas from the genus Acanthamoeba and their pathogenic properties. Ann. Parasitol. 2018, 64, 299–308.
  5. Kalra, S.K.; Sharma, P.; Shyam, K.; Tejan, N.; Ghoshal, U. Acanthamoeba and its pathogenic role in granulomatous amebic encephalitis. Exp. Parasitol. 2020, 208, 107788.
  6. Duggal, S.D.; Rongpharpi, S.R.; Duggal, A.K.; Kumar, A.; Biswal, I. Role of Acanthamoeba in granulomatous encephalitis: A review. J. Infect. Dis. Immune Ther. 2017, 1, 2.
  7. Parija, S.C.; Dinoop, K.; Venugopal, H. Management of granulomatous amebic encephalitis: Laboratory diagnosis and treatment. Trop. Parasitol. 2015, 5, 23–28.
  8. Lorenzo-Morales, J.; Khan, N.A.; Walochnik, J. An update on Acanthamoeba keratitis: Diagnosis, pathogenesis and treatment. Parasite 2015, 22, 10.
  9. Khan, N.A. Acanthamoeba: Biology and increasing importance in human health. FEMS Microbiol. Rev. 2006, 30, 564–595.
  10. Lorenzo-Morales, J.; Martín-Navarro, C.M.; López-Arencibia, A.; Arnalich-Montiel, F.; Piñero, J.E.; Valladares, B. Acanthamoeba keratitis: An emerging disease gathering importance worldwide? Trends Parasitol. 2013, 29, 181–187.
  11. Visvesvara, G.S. Infections with free-living amebae. Handb. Clin. Neurol. 2013, 114, 153–168.
  12. Taher, E.E.; Méabed, E.M.H.; Abdallah, I.; Abdel Wahed, W.Y. Acanthamoeba keratitis in noncompliant soft contact lenses users: Genotyping and risk factors, a study from Cairo, Egypt. J. Infect. Public Health 2018, 11, 377–383.
  13. Megha, K.; Sehgal, R.; Khurana, S. Genotyping of Acanthamoeba spp. isolated from patients with granulomatous amoebic encephalitis. Indian J. Med. Res. 2018, 148, 456–459.
  14. Gast, R.J.; Ledee, D.R.; Fuerst, P.A.; Byers, T.J. Subgenus systematics of Acanthamoeba: Four nuclear 18S rDNA sequence types. J. Eukaryot. Microbiol. 1996, 43, 498–504.
  15. Fuerst, P.A.; Booton, G.C.; Crary, M. Phylogenetic analysis and the evolution of the 18S rRNA gene typing system of Acanthamoeba. J. Eukaryot. Microbiol 2015, 62, 69–84.
  16. Fuerst, P.A.; Booton, G.C. Species, Sequence Types and Alleles: Dissecting Genetic Variation in Acanthamoeba. Pathogens 2020, 9, 534.
  17. Booton, G.C.; Kelly, D.J.; Chu, Y.W.; Seal, D.V.; Houang, E.; Lam, D.S.; Byers, T.J.; Fuerst, P.A. 18S ribosomal DNA typing and tracking of Acanthamoeba species isolates from corneal scrape specimens, contact lenses, lens cases, and home water supplies of Acanthamoeba keratitis patients in Hong Kong. J. Clin. Microbiol. 2002, 40, 1621–1625.
  18. Siddiqui, R.; Khan, N.A. Biology and pathogenesis of Acanthamoeba. Parasit. Vectors 2012, 10, 6.
  19. Behera, H.S.; Panda, A.; Satpathy, G.; Bandivadekar, P.; Vanathi, M.; Agarwal, T.; Nayak, N.; Tandon, R. Genotyping of Acanthamoeba spp. and characterization of the prevalent T4 type along with T10 and unassigned genotypes from amoebic keratitis patients in India. J. Med. Microbiol. 2016, 65, 370–376.
  20. Łanocha, N.; Kosik-Bogacka, D.; Maciejewska, A.; Sawczuk, M.; Wilk, A.; Kuźna-Grygiel, W. The occurence Acanthamoeba (Free Living Amoeba) in environmental and respiratory samples in Poland. Acta Protozool. 2009, 48, 271–279.
  21. Aichelburg, A.C.; Walochnik, J.; Assadian, O.; Prosch, H.; Steuer, A.; Perneczky, G.; Visvesvara, G.S.; Aspöck, H.; Vetter, N. Successful treatment of disseminated Acanthamoeba sp. infection with miltefosine. Emerg. Infect. Dis. 2008, 14, 1743–1746.
  22. Barete, S.; Combes, A.; de Jonckheere, J.F.; Datry, A.; Varnous, S.; Martinez, V.; Ptacek, S.G.; Caumes, E.; Capron, F.; Francès, C.; et al. Fatal disseminated Acanthamoeba lenticulata infection in a heart transplant patient. Emerg. Infect. Dis. 2007, 13, 736–738.
  23. Matsui, T.; Maeda, T.; Kusakabe, S.; Arita, H.; Yagita, K.; Morii, E.; Kanakura, Y. A case report of granulomatous amoebic encephalitis by Group 1 Acanthamoeba genotype T18 diagnosed by the combination of morphological examination and genetic analysis. Diagn. Pathol. 2018, 13, 27.
  24. Gavarāne, I.; Trofimova, J.; Mališevs, A.; Valciņa, O.; Kirjušina, M.; Rubeniņa, I.; Bērziņš, A. DNA extraction from amoebal isolates and genotype determination of Acanthamoeba from tap water in Latvia. Parasitol. Res. 2018, 117, 3299–3303.
  25. Javanmard, E.; Niyyati, M.; Lorenzo-Morales, J.; Lasjerdi, Z.; Behniafar, H.; Mirjalali, H. Molecular identification of waterborne free living amoebae (Acanthamoeba, Naegleria and Vermamoeba) isolated from municipal drinking water and environmental sources, Semnan province, north half of Iran. Exp. Parasitol. 2017, 183, 240–244.
  26. Derda, M.; Hadaś, E.; Wojtkowiak-Giera, A.; Wojt, W.J.; Cholewiński, M.; Skrzypczak, Ł. The occurrence of free-living amoebae in fountains. Probl. Hig. Epidemiol. 2013, 94, 147–150.
  27. Górnik, K.; Kuźna-Grygiel, W. Histological studies of selected organs of mice experimentally infected with Acanthamoeba spp. Folia Morphol. 2005, 64, 161–167.
  28. Łanocha-Arendarczyk, N.; Kosik-Bogacka, D.; Galant, K.; Zaorski, W.; Kot, K.; Łanocha, A. Pathogenic free-living amoeba. Post Mikrobiol. 2017, 1, 106–112.
  29. Clarke, B.; Sinha, A.; Parmar, D.N.; Sykakis, E. Advances in the diagnosis and treatment of Acanthamoeba keratitis. J. Ophthal Mol. 2012, 2012, 484–892.
  30. Brindley, N.; Matin, A.; Khan, N.A. Acanthamoeba castellanii: High antibody prevalence in racially and ethnically diverse populations. Exp. Parasitol. 2009, 121, 254–256.
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