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American Journal of Ophthalmology Feb 1996
Topics: Acanthamoeba; Acanthamoeba Keratitis; Animals; Cornea; Humans; Microscopy, Confocal
PubMed: 8623891
DOI: 10.1016/s0002-9394(14)70586-0 -
Ophthalmologica. Journal International... 2006To report cases of culture-proved Acanthamoeba keratitis in Greece over a 10-year period and to evaluate the effectiveness of the commonly used commercial contact lens... (Comparative Study)
Comparative Study
OBJECTIVES
To report cases of culture-proved Acanthamoeba keratitis in Greece over a 10-year period and to evaluate the effectiveness of the commonly used commercial contact lens disinfecting systems in clinical cases of Acanthamoeba keratitis.
MATERIAL AND METHODS
During the years 1994-2004, 45 contact lens wearers and 3 non-contact lens wearers presenting with symptoms and signs of keratitis underwent corneal sampling. The scrapings obtained were inoculated directly onto appropriate culture media for bacteria, fungi and Acanthamoeba. All proved positive for Acanthamoeba. The contact lenses and contact lens disinfecting solutions (16 one-step 3% hydrogen peroxide and 3 multipurpose solutions) of 19/45 patients with culture-proven Acanthamoeba keratitis were cultured for bacteria, fungi and Acanthamoeba.
RESULTS
Acanthamoeba was isolated from contact lenses and contact lens disinfecting solutions in all 19 cases of Acanthamoeba keratitis studied.
CONCLUSIONS
The main risk factor for corneal infection in contact lens wearers is the use of contact lens disinfecting systems ineffective at killing Acanthamoeba cysts and trophozoites, as well as bacteria and fungi. Improvement or development of new contact lens disinfecting systems by manufacturers is needed to prevent Acanthamoeba keratitis.
Topics: Acanthamoeba; Acanthamoeba Keratitis; Animals; Contact Lens Solutions; Contact Lenses; Drug Contamination; Greece; Humans; In Vitro Techniques; Incidence; Retrospective Studies; Risk Factors
PubMed: 16785754
DOI: 10.1159/000093077 -
Acta Tropica Nov 2006The free-living amoebae of the genus Acanthamoeba include non-pathogenic and pathogenic species and has been recently classified into 15 different genotypes, T1-T15. In...
The free-living amoebae of the genus Acanthamoeba include non-pathogenic and pathogenic species and has been recently classified into 15 different genotypes, T1-T15. In this study, a survey was conducted in order to determine the presence and pathogenic potential of free-living amoebae of Acanthamoeba genus in freshwater sources associated with human activities in the Nile Delta region, Egypt. Identification of Acanthamoeba was based on the morphology of cyst and trophozoite forms and PCR amplification with a genus specific primer pair. The pathogenic potential of Acanthamoeba isolates was characterized using temperature and osmotolerance assays and PCR reactions with two primer pairs specific to Acanthamoeba pathogenesis. Isolates genotypes were also determined after ribosomal DNA sequencing. These data revealed that isolates belong to T1, T2, T3, T4 and T7 genotypes. As expected, T4 isolates exhibited the most pathogenic traits and were osmotolerant, temperature tolerant and expressed extracellular serine proteases. This is the first report presenting environmental distribution of Acanthamoeba genotypes in Egypt.
Topics: Acanthamoeba; Animals; Egypt; Fresh Water; Genotype; Humans; Molecular Sequence Data; Osmolar Concentration; Phylogeny; Polymerase Chain Reaction; Public Health; Sequence Analysis, DNA; Serine Endopeptidases; Temperature; Water Supply
PubMed: 17078918
DOI: 10.1016/j.actatropica.2006.09.008 -
Acta Crystallographica. Section F,... Apr 2022Actophorin, which was recently tested for crystallization under microgravity on the International Space Station, was subjected to mutagenesis to identify a construct...
Actophorin, which was recently tested for crystallization under microgravity on the International Space Station, was subjected to mutagenesis to identify a construct with improved biophysical properties that were expected to improve the extent of diffraction. First, 20 mutations, including one C-terminal deletion of three residues, were introduced individually into actophorin, resulting in modest increases in thermal stability of between +0.5°C and +2.2°C. All but two of the stabilizing mutants increased both the rates of severing F-actin filaments and of spontaneous polymerization of pyrenyl G-actin in vitro. When the individual mutations were combined into a single actophorin variant, Acto-2, the overall thermal stability was 22°C higher than that of wild-type actophorin. When an inactivating S2P mutation in Acto-2 was restored, Acto-2/P2S was more stable by 20°C but was notably more active than the wild-type protein. The inactivating S2P mutation reaffirms the importance that Ser2 plays in the F-actin-severing reaction. The crystal structure of Acto-2 was solved to 1.7 Å resolution in a monoclinic space group, a first for actophorin. Surprisingly, despite the increase in thermal stability, the extended β-turn region, which is intimately involved in interactions with F-actin, is disordered in one copy of Acto-2 in the asymmetric unit. These observations emphasize the complex interplay among protein thermal stability, function and dynamics.
Topics: Acanthamoeba; Actins; Crystallization; Crystallography, X-Ray; Weightlessness
PubMed: 35400667
DOI: 10.1107/S2053230X22002448 -
Acta Crystallographica. Section F,... Dec 2021Actophorin, a protein that severs actin filaments isolated from the amoeba Acanthamoeba castellanii, was employed as a test case for crystallization under microgravity....
Actophorin, a protein that severs actin filaments isolated from the amoeba Acanthamoeba castellanii, was employed as a test case for crystallization under microgravity. Crystals of purified actophorin were grown under microgravity conditions aboard the International Space Station (ISS) utilizing an interactive crystallization setup between the ISS crew and ground-based experimenters. Crystals grew in conditions similar to those grown on earth. The structure was solved by molecular replacement at a resolution of 1.65 Å. Surprisingly, the structure reveals conformational changes in a remote β-turn region that were previously associated with actophorin phosphorylated at the terminal residue Ser1. Although crystallization under microgravity did not yield a higher resolution than crystals grown under typical laboratory conditions, the conformation of actophorin obtained from solving the structure suggests greater flexibility in the actophorin β-turn than previously appreciated and may be beneficial for the binding of actophorin to actin filaments.
Topics: Acanthamoeba; Actins; Crystallization; Crystallography, X-Ray; Weightlessness
PubMed: 34866600
DOI: 10.1107/S2053230X21011419 -
PloS One 2018The detection and identification of two endocytobiotic bacterial strains, one affiliated to the "Candidatus Caedibacter acanthamoebae"/"Ca. Paracaedimonas acanthamoeba",...
The detection and identification of two endocytobiotic bacterial strains, one affiliated to the "Candidatus Caedibacter acanthamoebae"/"Ca. Paracaedimonas acanthamoeba", and another to the endosymbiont of Acanthamoeba UWC8 and "Ca. Jidaibacter acanthamoeba" are described. For endocytobiont screening, we developed a PCR method with a set of broad-range bacterial 16S rRNA primers to substitute the commonly used but technically demanding fluorescent in situ hybridization technique. Our PCR test alone without sequencing failed to discriminate the endocytobiont-containing and endocytobiont-free Acanthamoeba sp. due to the presence of mismatched primers to host mitochondrial DNA. We highlighted the need to perform bacterial primer checking against the Acanthamoeba genome to avoid false positive detection in PCR. Although the genetic aspect of "Ca. Caedibacter acanthamoebae"/"Ca. Paracaedimonas acanthamoeba" and the endosymbiont of Acanthamoeba UWC8/"Ca. Jidaibacter acanthamoeba" are well studied, knowledge pertaining to their morphologies are quite vague. Hence, we used transmission electron microscopy to examine our endocytobionts which are affiliated to previously described intracellular bacteria of Acanthamoeba sp. We used good-quality TEM images for the localization and the fate of the current endocytobionts inside different life stages of the hosts. Furthermore, to the best of our knowledge, our TEM findings are the first to provide morphological evidence for the clearance of defective Acanthamoeba endocytobionts via an autophagic-like process.
Topics: Acanthamoeba; Alphaproteobacteria; DNA, Bacterial; DNA, Mitochondrial; Genome, Bacterial; Host-Pathogen Interactions; Microscopy, Electron, Transmission; RNA, Ribosomal, 16S
PubMed: 30356282
DOI: 10.1371/journal.pone.0204732 -
Infection and Immunity Feb 1997Acanthamoeba keratitis is a sight-threatening corneal infection. In a recent study, the saccharide mannose has been shown to inhibit the binding of Acanthamoeba...
Acanthamoeba keratitis is a sight-threatening corneal infection. In a recent study, the saccharide mannose has been shown to inhibit the binding of Acanthamoeba organisms to the epithelium of the cornea (L. D. Morton, G. L. McLaughlin, and H. E. Whiteley, Infect. Immun. 59:3819-3822, 1991). In an attempt to determine the molecular mechanism by which acanthamoebae adhere to the surface of the cornea, the present study was designed to determine whether Acanthamoeba castellanii derived from an infected human cornea (i) binds to mannose-containing glycoproteins (mannose-GPs) of corneal epithelium and (ii) expresses one or more mannose-binding proteins. Mannose-GPs of primary cell cultures of rabbit corneal epithelium were isolated by using three different agarose-conjugated, mannose-specific lectins. By electrophoresis blot-overlay assays, 35S-labeled acanthamoebae were shown to bind to mannose-GPs of corneal epithelium and to a neoglycoprotein, mannose-bovine serum albumin (mannose-BSA). 35S-labeled acanthamoebae also bound to microtiter wells coated with mannose-BSA in a concentration-dependent manner. The binding of amoebae to mannose-GPs was blocked by free methyl-alpha-D-mannopyranoside. The parasites did not bind to galactose-BSA or to many other proteins lacking mannose residues. A membrane-associated mannose-binding protein (136 kDa) of A. castellanii was isolated by affinity chromatography of detergent extracts of unlabeled parasites and of cell surface biotin-labeled parasites on a p-aminophenyl alpha-D-mannopyranoside-agarose column. The affinity-purified protein of the amoeba was shown to bind specifically to mannose-BSA. In summary, a mannose-binding protein is present on the surface membranes of Acanthamoeba, and corneal epithelial cells express Acanthamoeba-reactive GPs. One of the mechanisms of Acanthamoeba adhesion to the corneal surface may involve interactions between the mannose-binding protein of Acanthamoeba and mannose-GPs on the surface of corneal epithelium.
Topics: Acanthamoeba; Acanthamoeba Keratitis; Animals; Carrier Proteins; Cell Adhesion; Cornea; Epithelium; Eye Proteins; Glycoproteins; Host-Parasite Interactions; Humans; Mannose; Mannose-Binding Lectins; Methylmannosides; Rabbits
PubMed: 9009294
DOI: 10.1128/iai.65.2.439-445.1997 -
The Journal of Infection Jan 1998Stages in the encystment and excystment processes of Acanthamoeba castellanii have been studied. The kinetics of encystment involved measurements of the three phases...
Stages in the encystment and excystment processes of Acanthamoeba castellanii have been studied. The kinetics of encystment involved measurements of the three phases (pre-encystment, cyst initiation and cyst wall synthesis). Excystment, starting from a mature cyst, involved pre-emergence, penetration outwards of the cyst wall and free trophozoite. The sensitivity to biocides of trophozoites in the exponential growth phase, pre-encystment trophozoites, mature cysts and pre-excystment cysts has been investigated. Some differences in relative sensitivity to a bisbiguanide (chlorhexidine) and a polymeric biguanide (polyhexamethylene biguanide) were observed, but mature cysts were always the most resistant cellular form.
Topics: Acanthamoeba; Animals; Biguanides; Chlorhexidine; Disinfectants; Life Cycle Stages
PubMed: 9515667
DOI: 10.1016/s0163-4453(98)93054-7 -
Parasitology Research Feb 2018Free-living amoebae of the genus Acanthamoeba are potentially pathogenic protozoa widespread in the environment. The detection/diagnosis as well as environmental survey...
Free-living amoebae of the genus Acanthamoeba are potentially pathogenic protozoa widespread in the environment. The detection/diagnosis as well as environmental survey strategies is mainly based on the identification of the 18S rDNA sequences of the strains that allow the recovery of various distinct genotypes/subgenotypes. The accurate recording of such data is important to better know the environmental distribution of distinct genotypes and how they may be preferentially associated with disease. Recently, a putative new acanthamoebal genotype T99 was introduced, which comprises only environmental clones apparently with some anomalous features. Here, we analyze these sequences through partial treeing and BLAST analyses and find that they are actually chimeras. Our results show that the putative T99 genotype is very likely formed by chimeric sequences including a middle fragment from acanthamoebae of genotype T13, while the 5'- and 3'-end fragments came from a nematode and a cercozoan, respectively. Molecular phylogenies of Acanthamoeba including T99 are consequently erroneous as genotype T99 does not exist in nature. Careful identification of Acanthamoeba genotypes is therefore critical for both phylogenetic and diagnostic applications.
Topics: Acanthamoeba; Chimera; DNA, Protozoan; DNA, Ribosomal; Genotype; Phylogeny; RNA, Ribosomal, 18S
PubMed: 29177581
DOI: 10.1007/s00436-017-5690-9 -
Revista Argentina de Microbiologia 2017Free-living Amoebae of Acanthamoeba genus include non-pathogenic and pathogenic strains that are currently classified in 18 different genotypes, T1-T18. In this study, a...
Free-living Amoebae of Acanthamoeba genus include non-pathogenic and pathogenic strains that are currently classified in 18 different genotypes, T1-T18. In this study, a survey was carried out to evaluate the presence of Acanthamoeba strains inwatering trough sample in La Pampa province, Argentina. Sample were inoculated onto non-nutrient agar plates and were checked for the presence of Acanthamoeba. Polymerase chain reaction was performed with genus-specific primers JDP1/JDP2, followed by direct sequencing of the polymerase chain reaction product for molecular identification. Sequencing results revealed the presence of T4, T5 and T15 genotypes within the studied samples. Sequencing revealed presence of T4, T5 and T15 in the samples studied genotypes, the most frequent T4. Our study reveals importance of the presence of Acanthamoeba in the livestock environment and the need for further studies to associate the presence of these organisms and the role in veterinary pathology. To the best of our knowledge, this is the first report demonstrating the presence Acanthamoeba in La Pampa province and the first study at the genotype level in Argentina.
Topics: Acanthamoeba; Argentina; Genotype; Polymerase Chain Reaction; Water; Water Microbiology
PubMed: 28495034
DOI: 10.1016/j.ram.2016.12.003