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Microorganisms
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Advances in Acanthamoeba
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Advances in Acanthamoeba

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Parasitology".

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 12986

Special Issue Editor

Dr. Daniele Corsaro

E-Mail Website
Guest Editor
CHLAREAS, 12, rue du Maconnais, F-54500 Vandoeuvre-lès-Nancy, France
Interests: microbiology; free-living amoebae; molecular biology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Acanthamoeba spp. are the most widespread free-living amoebae worldwide, frequently found in both natural and human-made environments. The role of Acanthamoeba as an opportunistic pathogen in humans and other animals is established: the amoeba preferentially attacks the cornea causing amoebic keratitis (AK) with loss of vision, but it can also enter the body of the host by other routes, leading to disseminated infections, which can result in fatal granulomatous amoebic encephalitis (GAE). Like most free-living amoebae, Acanthamoeba also carries other microbes, some of which are potentially pathogenic, thus facilitating their environmental spread.

Over the past twenty years, many studies have been conducted to clarify evolutionary relationships within Acanthamoeba, improve diagnosis and epidemiology, elucidate pathogenic mechanisms, develop environmental monitoring strategies, as well as examine various approaches for treatment.

This Special Issue aims to bring together relevant original articles and review papers reporting on recent advances in various topics of Acanthamoeba research.

Dr. Daniele Corsaro
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Microorganisms is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • acanthamoeba
  • genotype
  • molecular phylogeny
  • environmental distribution
  • ecology
  • epidemiology
  • diagnostic tools
  • human and animal diseases
  • pathogenesis
  • amoeba-host interaction
  • antiamoebic drugs

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Published Papers (8 papers)

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Editorial

Jump to: Research, Review

2 pages, 170 KiB  
Editorial
Editorial for the Special Issue “Advances in Acanthamoeba”
by Daniele Corsaro
Microorganisms 2024, 12(5), 865; https://doi.org/10.3390/microorganisms12050865 - 26 Apr 2024
Viewed by 724
Abstract
Some free-living amoebae can behave as opportunistic parasites, causing rare but dangerous diseases in humans and animals, primarily amoebic keratitis, with loss of vision, and encephalitis, which is almost always fatal [...] Full article
(This article belongs to the Special Issue Advances in Acanthamoeba)

Research

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14 pages, 1379 KiB  
Article
Acanthamoeba Sequence Types and Allelic Variations in Isolates from Clinical and Different Environmental Sources in Italy
by Federica Berrilli, Margherita Montalbano Di Filippo, Isabel Guadano-Procesi, Marta Ciavurro and David Di Cave
Microorganisms 2024, 12(3), 544; https://doi.org/10.3390/microorganisms12030544 - 8 Mar 2024
Cited by 2 | Viewed by 1367
Abstract
The genus Acanthamoeba comprises free-living amoebae distributed in a wide variety of environments. These amoebae are clinically significant, causing opportunistic infections in humans and other animals. Despite this, limited data on Acanthamoeba sequence types and alleles are available in Italy. In the present [...] Read more.
The genus Acanthamoeba comprises free-living amoebae distributed in a wide variety of environments. These amoebae are clinically significant, causing opportunistic infections in humans and other animals. Despite this, limited data on Acanthamoeba sequence types and alleles are available in Italy. In the present study, we analyzed all Acanthamoeba sequences deposited from Italy with new positive Acanthamoeba clinical samples from symptomatic AK cases, to provide an overview of the genetic variants’ spatial patterns from different sources within the Italian context. A total of 137 Acanthamoeba sequences were obtained. Six sequence types were identified: T2/6, T3, T4, T11, T13, and T15. Only T4 and T15 were found in both sources. The Acanthamoeba T4 sequence type was found to be the most prevalent in all regions, accounting for 73% (100/137) of the Italian samples analyzed. The T4 sequence type demonstrated significant allelic diversity, with 30 distinct alleles from clinical and/or environmental samples. These outcomes enabled a better understanding of the distribution of Acanthamoeba isolates throughout Italy, reaffirming its well-recognized ubiquity. Acanthamoeba isolates analysis from keratitis, together with the environmental strains monitoring, might provide important information on different genotypes spreading. This might be useful to define the transmission pathways of human keratitis across different epidemiological scales. Full article
(This article belongs to the Special Issue Advances in Acanthamoeba)
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8 pages, 1348 KiB  
Communication
Influence of the Age of Free-Living Amoeba Cysts on Their Vertical Distribution in a Water Column
by Zineb Fechtali-Moute and Sébastien Pomel
Microorganisms 2024, 12(3), 474; https://doi.org/10.3390/microorganisms12030474 - 27 Feb 2024
Cited by 1 | Viewed by 1021
Abstract
Free-living amoebae (FLA) are widely distributed protozoa in both natural and artificial environments such as drinking water. In addition to the ability of all FLA to transport various pathogenic microorganisms, certain species, such as Acanthamoeba spp. or Balamuthia mandrillaris, have intrinsic pathogenic [...] Read more.
Free-living amoebae (FLA) are widely distributed protozoa in both natural and artificial environments such as drinking water. In addition to the ability of all FLA to transport various pathogenic microorganisms, certain species, such as Acanthamoeba spp. or Balamuthia mandrillaris, have intrinsic pathogenic abilities and cause severe cerebral infections. Previous work has shown an enrichment of FLA cysts in biofilm developed in upper levels of Drinking Water Storage Towers (DWSTs), suggesting that differences in densities of FLA cysts may play a role in their unequal distribution in the water column. To evaluate this hypothesis, a model of a water column was created for this study and used to analyze the vertical distribution of cysts of the FLA Acanthamoeba castellanii, Vermamoeba vermiformis, and Balamuthia mandrillaris from 0 to 23 weeks. Interestingly, our data showed that the cysts of both A. castellanii and V. vermiformis were enriched in upper water levels during their aging. However, B. mandrillaris cysts were equally distributed in the water column during the entire study. These results show that, in addition to the role of water level variation in the DWST, some FLA cysts can become less dense during their aging, which contributes to their enrichment in upper water and therefore biofilm levels. Full article
(This article belongs to the Special Issue Advances in Acanthamoeba)
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9 pages, 683 KiB  
Communication
mRNA Sequencing Reveals Upregulation of Glutathione S-Transferase Genes during Acanthamoeba Encystation
by Alvaro de Obeso Fernández del Valle, Christian Quintus Scheckhuber, David Armando Chavaro-Pérez, Erandi Ortega-Barragán and Sutherland K. Maciver
Microorganisms 2023, 11(4), 992; https://doi.org/10.3390/microorganisms11040992 - 11 Apr 2023
Cited by 6 | Viewed by 1846
Abstract
Some members of the genus Acanthamoeba are facultative pathogens typically with a biphasic lifestyle: trophozoites and cysts. Acanthamoeba is capable of infecting the cornea, resulting in Acanthamoeba keratitis. The cyst is one of the key components for the persistence of infection. Gene expression [...] Read more.
Some members of the genus Acanthamoeba are facultative pathogens typically with a biphasic lifestyle: trophozoites and cysts. Acanthamoeba is capable of infecting the cornea, resulting in Acanthamoeba keratitis. The cyst is one of the key components for the persistence of infection. Gene expression during Acanthamoeba encystation showed an upregulation of glutathione S-transferase (GST) genes and other closely related proteins. mRNA sequencing showed GST, and five genes with similar sequences were upregulated after 24 h of inducing encystation. GST overexpression was verified with qPCR using the HPRT and the cyst-specific protein 21 genes as controls. The GST inhibitor ethacrynic acid was found to decrease cell viability by 70%. These results indicate a role of GST in successful encystation, possibly by maintaining redox balance. GST and associated processes could be targets for potential treatments alongside regular therapies to reduce relapses of Acanthamoeba infection. Full article
(This article belongs to the Special Issue Advances in Acanthamoeba)
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8 pages, 1223 KiB  
Communication
Presence of Free-living Acanthamoeba in Loa and Salado Rivers, Atacama Desert, Northern Chile
by Camila Salazar-Ardiles, Alexander Pérez-Arancibia, Leyla Asserella-Rebollo and Benito Gómez-Silva
Microorganisms 2022, 10(12), 2315; https://doi.org/10.3390/microorganisms10122315 - 23 Nov 2022
Cited by 4 | Viewed by 1834
Abstract
Substantial knowledge has accumulated on the microbiome of the hyperarid Atacama Desert during the last two decades; however, information on Atacama free-living amoebae (FLA) is limited and increasing efforts are required. FLA are polyphyletic heterotrophic naked or testate protists that feed on organic [...] Read more.
Substantial knowledge has accumulated on the microbiome of the hyperarid Atacama Desert during the last two decades; however, information on Atacama free-living amoebae (FLA) is limited and increasing efforts are required. FLA are polyphyletic heterotrophic naked or testate protists that feed on organic matter, fungi, protozoa, and bacteria and may disseminate infections. Amoebae in Chile are represented by 416 taxa and 64 genera, and 29 taxa have been identified in arid shrub lands at the southern limit of the Atacama Desert, and Acanthamoeba are present in all the country’s regions. To expand our knowledge and to contribute to the biogeographic distribution of Atacama FLA, we report the dominant presence of members of the genus Acanthamoeba in water and sediment sampled at the Loa and Salado rivers in the pre-Andean zone of the Antofagasta Region, northern Chile, at sites 2500 m above sea level. We expect these observations and preliminary evidence of FLA presence in other wetlands (Chiuchiu, Tebenquiche) in this region to be incentive for further exploration of Atacama amoebae. Full article
(This article belongs to the Special Issue Advances in Acanthamoeba)
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13 pages, 1636 KiB  
Article
Acanthamoeba Mannose and Laminin Binding Proteins Variation across Species and Genotypes
by Daniele Corsaro
Microorganisms 2022, 10(11), 2162; https://doi.org/10.3390/microorganisms10112162 - 31 Oct 2022
Cited by 13 | Viewed by 1746
Abstract
Acanthamoeba is a ubiquitous free-living amoeba capable of being an opportunistic pathogen in humans and animals. A critical step in infection is the adhesion of the amoeba to host cells and tissues, and two major parasite adhesins, mannose-binding protein (MBP) and laminin-binding protein [...] Read more.
Acanthamoeba is a ubiquitous free-living amoeba capable of being an opportunistic pathogen in humans and animals. A critical step in infection is the adhesion of the amoeba to host cells and tissues, and two major parasite adhesins, mannose-binding protein (MBP) and laminin-binding protein (LBP), are known to recognize the cell surface glycoproteins and those of the extracellular matrix, respectively. In this study, the available genomes of Acanthamoeba were analysed to recover the sequences of MBP and LBP using previously published genetic data. Genes for both proteins were successfully obtained from strains belonging to various genotypes (T4A, T4D, T4G, T4F, T2, T5, T10, T22, T7 and T18), resulting in a single gene for LBP but identifying two types of MBP, MBP1 and MBP2. Phylogenetic analysis based on deduced amino acid sequences shows that both MBP and LBP have a branching pattern that is consistent with that based on 18S rDNA, indicating that changes in both proteins occurred during diversification of Acanthamoeba lines. Notably, all MBPs possess a conserved motif, shared with some bacterial C-type lectins, which could be the recognition site for mannose binding. Full article
(This article belongs to the Special Issue Advances in Acanthamoeba)
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13 pages, 2112 KiB  
Article
Exploring LSU and ITS rDNA Sequences for Acanthamoeba Identification and Phylogeny
by Daniele Corsaro
Microorganisms 2022, 10(9), 1776; https://doi.org/10.3390/microorganisms10091776 - 3 Sep 2022
Cited by 9 | Viewed by 1677
Abstract
The identification and classification of strains of Acanthamoeba, a potentially pathogenic ubiquitous free-living amoeba, are largely based on the analysis of 18S rDNA sequences, currently delineating 23 genotypes, T1 to T23. In this study, the sequences of the ITS region, i.e., the [...] Read more.
The identification and classification of strains of Acanthamoeba, a potentially pathogenic ubiquitous free-living amoeba, are largely based on the analysis of 18S rDNA sequences, currently delineating 23 genotypes, T1 to T23. In this study, the sequences of the ITS region, i.e., the 5.8S rDNA and the two internal transcribed spacers (ITS-1 and ITS-2), and those of the large subunit (LSU) rDNA of Acanthamoeba were recovered from amoeba genomes; the sequences are available in GenBank. The complete ITS–LSU sequences could be obtained for 15 strains belonging to 7 distinct lineages (T4A, T4D, T4F, T4G, T2, T5, and T18), and the site of the hidden break producing the 26Sα and 26Sβ was identified. For the other lines, either the LSU is partial (T2/T6, T7) or the ITS is fragmentary (T7, T10, T22). It is noteworthy that a number of sequences assigned to fungi turned out to actually be Acanthamoeba, only some of which could be affiliated with known genotypes. Analysis of the obtained sequences indicates that both ITS and LSU are promising for diagnostic and phylogenetic purposes. Full article
(This article belongs to the Special Issue Advances in Acanthamoeba)
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Review

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23 pages, 1281 KiB  
Review
The Status of Molecular Analyses of Isolates of Acanthamoeba Maintained by International Culture Collections
by Paul A. Fuerst
Microorganisms 2023, 11(2), 295; https://doi.org/10.3390/microorganisms11020295 - 23 Jan 2023
Cited by 6 | Viewed by 1800
Abstract
Acanthamoeba is among the most ubiquitous protistan groups in nature. Knowledge of the biological diversity of Acanthamoeba comes in part from the use of strains maintained by the major microbial culture collections, ATCC and CCAP. Standard strains are vital to ensure the comparability [...] Read more.
Acanthamoeba is among the most ubiquitous protistan groups in nature. Knowledge of the biological diversity of Acanthamoeba comes in part from the use of strains maintained by the major microbial culture collections, ATCC and CCAP. Standard strains are vital to ensure the comparability of research. The diversity of standard strains of Acanthamoeba in the culture collections is reviewed, emphasizing the extent of genotypic studies based on DNA sequencing of the small subunit ribosomal RNA from the nucleus (18S rRNA gene; Rns) or the mitochondria (16S-like rRNA gene; rns). Over 170 different strains have been maintained at some time by culture centers. DNA sequence information is available for more than 70% of these strains. Determination of the genotypic classification of standard strains within the genus indicates that frequencies of types within culture collections only roughly mirror that from clinical or environmental studies, with significant differences in the frequency of some genotypes. Culture collections include the type of isolate from almost all named species of Acanthamoeba, allowing an evaluation of the validity of species designations. Multiple species are found to share the same Sequence Type, while multiple Sequence Types have been identified for different strains that share the same species name. Issues of sequence reliability and the possibility that a small number of standard strains have been mislabeled when studied are also examined, leading to potential problems for comparative analyses. It is important that all species have reliable genotype designations. The culture collections should be encouraged to assist in completing the molecular inventory of standard strains, while workers in the Acanthamoeba research community should endeavor to ensure that strains representative of genotypes that are missing from the culture collection are provided to the culture centers for preservation. Full article
(This article belongs to the Special Issue Advances in Acanthamoeba)
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