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Acta Microbiologica Et Immunologica... Sep 2019Genus is an opportunistic protozoan that is widely distributed in the environment. Within this genus, numerous species are recognized as human pathogens, potentially...
Genus is an opportunistic protozoan that is widely distributed in the environment. Within this genus, numerous species are recognized as human pathogens, potentially causing keratitis (AK). AK is a corneal disease, associated predominantly with contact lens (CL) wear; its epidemiology is related to the specific genotypes. This study reports seven CL wearer, PCR-positive patients with AK, diagnosed between January 2015 and 2018. Patients had the diagnosis of AK 1.36 months after first symptoms. Genotyping allowed the identification of six isolates of the T4 and one of the T8 genotypes. At first presentation, pseudendritiformic epithelopathy/dirty epithelium (four eyes, 57.1%), multifocal stromal infiltrates (five eyes, 71.4%), ring infiltrate (three eyes, 42.8%), and perineuritis (one eye, 14.3%) were observed. AK was healed without later recurrence in two eyes (28.5%) using triple-topical therapy, in three eyes (42.8%) following additional penetrating keratoplasty. In one patient (14.3%), AK recurred following successful application of triple-therapy and was treated successfully with repeated triple-topical therapy and in one patient (14.3%), no follow-up data were available after diagnosis. We could not observe correlation of genotype and clinical course or the necessity of corneal transplantation in our case series.
Topics: Acanthamoeba; Acanthamoeba Keratitis; Administration, Topical; Adolescent; Adult; Antiprotozoal Agents; Corneal Transplantation; Female; Genotype; Genotyping Techniques; Humans; Hungary; Male; Middle Aged; Treatment Outcome; Young Adult
PubMed: 30835133
DOI: 10.1556/030.66.2019.008 -
Parasitology Research Apr 2007The capacity of Acanthamoeba to predate Cryptosporidium oocysts was demonstrated. A maximum of six oocysts per Acanthamoeba trophozoite were detected, and a slow...
The capacity of Acanthamoeba to predate Cryptosporidium oocysts was demonstrated. A maximum of six oocysts per Acanthamoeba trophozoite were detected, and a slow elimination of the internalized oocysts to the surrounding culture medium was observed. Free-living amoebae may act as carriers of Cryptosporidium oocysts and, thus, may play an important role in the transmission of cryptosporidiosis.
Topics: Acanthamoeba; Animals; Cryptosporidium; Feeding Behavior; Oocysts
PubMed: 17136384
DOI: 10.1007/s00436-006-0377-7 -
Parasitology Research May 2018Free-living amoeba of the genus Acanthamoeba can eventually act as parasites, causing infections in humans. Some physiological characteristics of Acanthamoeba have been...
Free-living amoeba of the genus Acanthamoeba can eventually act as parasites, causing infections in humans. Some physiological characteristics of Acanthamoeba have been related to the grade of pathogenicity, allowing inferences about the pathogenic potential. The main goal of this study was to characterize isolates of Acanthamoeba obtained in Brazil and evaluate properties associated with their pathogenicity. A total of 39 isolates obtained from keratitis cases (n = 16) and environmental sources (n = 23) were classified into morphological groups and genotyped by sequencing the 18S rDNA fragments ASA.S1 and GTSA.B1. Samples were also tested regarding their thermo-tolerance, osmo-tolerance, and cytopathogenicity in MDCK cells. Isolates were identified and classified as follows: group I (T17, T18); group II (T1, T3, T4, T11); and group III (T5, T15), with the predominance of genotype T4 (22/39). Clinical isolates were genotyped as T3 (1/16), T4 (14/16) and T5 (1/16). The majority of isolates (38/39) were able to grow at 37 °C, but tolerance to 40 °C was more frequent among environmental samples. The tolerance to 1 M mannitol was infrequent (4/39), with three of these corresponding to clinical samples. The variable ability to cause cytopathic effects was observed among isolates of distinct genotypes and origins. This study identified, for the first time, T1 and T18 in Brazil. It also indicated a weak association between the clinical origin of the isolates and tolerance to high temperatures, high osmolarity, and cytopathogenicity, demonstrating that some in vitro parameters do not necessarily reflect a higher propensity of Acanthamoeba to cause a disease.
Topics: Acanthamoeba; Acanthamoeba Keratitis; Animals; Brazil; Cell Line; DNA, Ribosomal; Dogs; Genotype; Hot Temperature; Humans; Madin Darby Canine Kidney Cells; Osmolar Concentration; RNA, Ribosomal, 18S; Thermotolerance
PubMed: 29532218
DOI: 10.1007/s00436-018-5824-8 -
European Journal of Protistology Oct 2017In order to improve our knowledge on the epidemiology of amoebic keratitis, as well as the identification of Acanthamoeba isolates, we have isolated Acanthamoeba spp....
In order to improve our knowledge on the epidemiology of amoebic keratitis, as well as the identification of Acanthamoeba isolates, we have isolated Acanthamoeba spp. from five symptomatic patients in Spain in the present study. All isolates were grown in axenic liquid medium, with only one exception. The morphology of these isolates were characterized by optical and scanning electron microscopy. Their structural features corresponded to those of amphizoic amoebae (namely Acanthamoeba spp.). The molecular characterization of the five Acanthamoeba isolates yielded six sequences. Almost complete 18S rRNA gene sequences (>2000bp) were obtained from three isolates and partial sequences (∼1500bp) from the other two. A robust phylogenetic analysis based on the almost complete 18S rRNA sequence showed that four isolates belonged to the T4 genotype and the other one to the T3 genotype. However, all isolates were identified as T4 genotype using the ASA.S1 fragment. As previously suggested by other researchers, only a robust phylogenetic approach may be helpful in identifying Acanthamoeba genotypes. In addition, new data on the phylogenetic relationships among the Acanthamoeba genotypes is provided and discussed.
Topics: Acanthamoeba; Acanthamoeba Keratitis; Genotype; Humans; Microscopy, Electron, Scanning; Phylogeny; RNA, Ribosomal, 18S; Spain; Species Specificity
PubMed: 28756938
DOI: 10.1016/j.ejop.2017.06.009 -
Journal of Virology Mar 2015Acanthamoeba is a genus of free-living amoebas distributed worldwide. Few studies have explored the interactions between these protozoa and their infecting giant virus,...
Acanthamoeba is a genus of free-living amoebas distributed worldwide. Few studies have explored the interactions between these protozoa and their infecting giant virus, Acanthamoeba polyphaga mimivirus (APMV). Here we show that, once the amoebal encystment is triggered, trophozoites become significantly resistant to APMV. Otherwise, upon infection, APMV is able to interfere with the expression of a serine proteinase related to amoebal encystment and the encystment can no longer be triggered.
Topics: Acanthamoeba; Host-Parasite Interactions; Mimiviridae; Serine Proteases; Spores, Protozoan
PubMed: 25520511
DOI: 10.1128/JVI.03177-14 -
Reviews of Infectious Diseases 1991Evidence for subdivision of the cell cycle of Acanthamoeba into ultradian biochemical cycles is accumulating, and a linkage between these cycles and the length of the... (Review)
Review
Evidence for subdivision of the cell cycle of Acanthamoeba into ultradian biochemical cycles is accumulating, and a linkage between these cycles and the length of the cell cycle is possible. The DNA replication cycle differs with the method of assay: no G1 phase is found in asynchronous cultures, and a long G1 phase is found in synchronous cultures. Encystment most likely occurs from G2, but whether it is limited to a portion of this phase is not clear. Encystment-enhancing factors are released by Acanthamoeba castellanii and Acanthamoeba palestinensis, and encystment can be induced by monoclonal antibodies to plasma membrane proteins. Likewise, encystment can be induced by inhibitors of polyamine synthesis, especially diamidines that inhibit S-adenosylmethionine decarboxylase, but inhibition of this enzyme is not necessarily responsible for differentiation. Studies on the regulation of gene expression during encystment have focused on actin and the ribosomal RNA transcriptional unit.
Topics: Acanthamoeba; Animals; Antiprotozoal Agents; Cell Cycle; Cell Differentiation; DNA Replication; DNA, Protozoan; Diminazene; Gene Expression Regulation; Polyamines
PubMed: 2047666
DOI: 10.1093/clind/13.supplement_5.s373 -
Parasitology Research Jul 2012Adenoviruses are important pathogens which are responsible for human enteritic, respiratory and eye infections. These viruses have been found to be prevalent in several...
Adenoviruses are important pathogens which are responsible for human enteritic, respiratory and eye infections. These viruses have been found to be prevalent in several natural and artificial water reservoirs worldwide. Free-living amoebae (FLA) have been recovered from similar water reservoirs, and it has been shown that FLA may act as reservoirs or vehicles of various microorganisms living in the same environment. To examine the ability of FLA to harbour adenoviruses, an in vitro study was conducted. Several Acanthamoeba strains were ‘co-cultivated’ with adenoviruses (adenoviruses 11 and 41), grown on A549 cells, using a proven test protocol. After phagocytosis and ingestion, the adenoviruses could be found within the cytoplasm of the Acanthamoeba trophozoites. The intake of the viruses into the cytoplasm of the trophozoites was demonstrated in an Acanthamoeba castellanii strain with the help of fluorescence microscopy and electron microscopy. An adenovirus DFA kit, which utilizes a direct immunofluorescent antibody technique for identifying adenovirus in infected tissue cultures, was used. In our study, it was demonstrated that adenoviruses were incorporated into the host amoebae (Acanthamoeba sp. Grp. II, three strains). So far, there were only a few publications concerning the relationship of free-living amoebae and viruses; only one of these described the detection of adenoviruses within acanthamoebae with molecular biological methods. We conducted this descriptive study to further examine the association between viable adenoviruses and FLA. To our knowledge, this is the first study to demonstrate directly the adenoviruses within FLA as vectors and vehicles. Therefore, we concluded that free-living amoebae appear able to act as carriers or vectors of the adenoviruses and thus may play a certain role in the dispersal of adenoviruses.
Topics: Acanthamoeba; Adenoviruses, Human; Cell Line; Cytoplasm; Epithelial Cells; Humans; Microscopy, Electron; Microscopy, Fluorescence; Phagocytosis
PubMed: 22290448
DOI: 10.1007/s00436-012-2828-7 -
Experimental Parasitology Apr 2013Observations on cultured Acanthamoeba royreba trophozoites and in vitro cytopathogenicity of this amoeba are described. In culture, amoebae were active, pleomorphic and...
Observations on cultured Acanthamoeba royreba trophozoites and in vitro cytopathogenicity of this amoeba are described. In culture, amoebae were active, pleomorphic and moved on the substrate by producing endocytic structures and emitting slight cytoplasmic microprojections from the cell surface. These projections were formed by hyaline cytoplasm and they were related to motion structures such as acanthopodia and lamellipodia, in which actin provides a framework that allows rapid changes in morphology. In the cytoplasm abundant vacuoles of different size and content were seen. By means of electron microscopy, it was possible to observe the compact fibrogranular appearance of the cytoplasm, along with the main cellular organelles such as the Golgi complex, the endoplasmic reticulum, digestive vacuoles, mitochondria and contractile vacuoles. Incubation of MDCK epithelial cell monolayers with conditioned medium did not produce a significant structural damage to the monolayer, even after 24h of incubation. When the trophozoites were incubated with the target cells the monolayer exhibited a clear injury created by the amoebae, which produced focal damage. Nevertheless, the rest of the monolayer appeared to remain intact, suggesting that a contact-dependent interaction is necessary to damage the target cells. These observations demonstrate the low invasive capacity of this amoeba.
Topics: Acanthamoeba; Acanthamoeba Keratitis; Animals; Axenic Culture; Brain; Culture Media, Conditioned; Dogs; Humans; Lung; Madin Darby Canine Kidney Cells; Male; Mice; Mice, Inbred BALB C; Microscopy, Confocal; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Microscopy, Phase-Contrast
PubMed: 23357648
DOI: 10.1016/j.exppara.2013.01.011 -
The Korean Journal of Parasitology Oct 2019Acanthamoeba keratitis (AK) is a rare sight-threatening corneal infection, often reporting from contact lens wearers. An asymptomatic human immunodeficiency virus...
Acanthamoeba keratitis (AK) is a rare sight-threatening corneal infection, often reporting from contact lens wearers. An asymptomatic human immunodeficiency virus (HIV)-infected Thai male without history of contact lens use complained foreign body sensation at his left eye during motorbike riding. He had neither specific keratitis symptoms nor common drugs responding, which contributed to delayed diagnosis. By corneal re-scraping, Acanthamoeba-like cysts were detected by calcofluor white staining and agar culture. The etiological agent obtained from the culture was molecularly confirmed by Acanthamoeba spp.-specific PCR, followed by DNA sequencing. The results from BLAST and phylogenetic analysis based on the DNA sequences, revealed that the pathogen was Acanthamoeba T4, the major genotype most frequently reported from clinical isolates. The infection was successfully treated with polyhexamethylene biguanide resulting in corneal scar. This appears the first reported AK case from a non-contact lens wearer with HIV infection in Thailand. Although AK is sporadic in developing countries, a role of free-living Acanthamoeba as an opportunistic pathogen should not be neglected. The report would increase awareness of AK, especially in the case presenting unspecific keratitis symptoms without clinical response to empirical antimicrobial therapy.
Topics: Acanthamoeba; Acanthamoeba Keratitis; Adult; Asymptomatic Diseases; Eye; HIV Infections; Humans; Male; Phylogeny; Thailand
PubMed: 31715691
DOI: 10.3347/kjp.2019.57.5.505 -
Parasites & Vectors Jan 2019Acanthamoeba spp. are the causative agents of a severe keratitis occurring mainly in contact lens wearers. The genus comprises more than 24 species that are currently...
BACKGROUND
Acanthamoeba spp. are the causative agents of a severe keratitis occurring mainly in contact lens wearers. The genus comprises more than 24 species that are currently divided into 20 different genotypes (T1-T20) according to sequence variations in the 18S rRNA gene. The objective of this study was to identify the genotypes and sub-genotypes of Acanthamoeba isolates collected at the Parasitology Laboratory of the Public Health Institute of Chile, the only laboratory in the country where Acanthamoeba screening is performed. This is the first report of genotypic identification of clinical isolates of Acanthamoeba in Chile and one of the few in South America.
RESULTS
In this study, 114 Acanthamoeba isolates from 76 Acanthamoeba keratitis patients, obtained between 2005-2016, were genotyped. T4 was the predominant genotype; T2 and T11 genotypes, which are scarcely reported worldwide, were also identified in Chilean patients (one and two patients, respectively). This is the first report of T2 and T11 genotypes isolated from Acanthamoeba keratitis patients in South America. It is also the first report of the T2 genotype circulating in this continent. Analysis of the diagnostic fragment 3 region of the 18S rRNA gene showed 24 T4 variants, with a predominance of the sub-genotype T4/A, followed by T4/B, T4/G, T4/C and T4/D. Bayesian analysis revealed three groups among the T4 variants: two well supported groups that included 12 and 7 sub-genotypes, respectively, and a weakly supported group that included 5 sub-genotypes. Most of the predominant T4 sub-genotypes belonged to the same group, which included 71.3% of the patients, while some minority variants lied mainly in the other two clusters.
CONCLUSIONS
T2, T4 and T11 genotypes were predominantly isolated from the Acanthamoeba keratitis patients in Chile. Chilean predominant T4 sub-genotypes, which have also been reported worldwide, formed a separate cluster of the minority T4 variants. This study provides useful information about the predominant genotypes and subgenotypes that would be useful in selecting suitable strains to develop immunological and/or molecular diagnostic assays in Chile.
Topics: Acanthamoeba; Acanthamoeba Keratitis; Chile; Female; Genetic Variation; Genotype; Humans; Male; Phylogeny
PubMed: 30683157
DOI: 10.1186/s13071-019-3302-5