Search results for "Acanthamoeba"
showing 10 items of 13 documents
Roles for RpoS in survival of Escherichia coli during protozoan predation and in reduced moisture conditions highlight its importance in soil environ…
2017
The soil is a complex ecosystem where interactions between biotic and abiotic factors determine the survival and fate of microbial inhabitants of the system. Having previously shown that Escherichia coli requires the general stress response regulator, RpoS, to survive long term in soil, it was important to determine what specific conditions in this environment necessitate a functional RpoS. This study investigated the susceptibility of soil-persistent E. coli to predation by the single-celled eukaryotes Acanthamoeba polyphaga and Tetrahymena pyriformis, and the role RpoS plays in resisting this predation. Strain-specific differences were observed in the predation of E. coli strains, with so…
Mimiviruses and the Human Interferon System: Viral Evasion of Classical Antiviral Activities, But Inhibition By a Novel Interferon-β Regulated Immuno…
2017
International audience; In this review we discuss the role of mimiviruses as potential human pathogens focusing on clinical and evolutionary evidence. We also propose a novel antiviral immunomodulatory pathway controlled by interferon-beta (IFN-beta) and mediated by immune-responsive gene 1 (IRG1) and itaconic acid, its product. Acanthamoeba polyphaga Mimivirus (APMV) was isolated from amoebae in a hospital while investigating a pneumonia outbreak. Mimivirus ubiquity and role as protist pathogens are well understood, and its putative status as a human pathogen has been gaining strength as more evidence is being found. The study of APMV and human cells interaction revealed that the virus is …
Lack of evidence of mimivirus replication in human PBMCs
2018
The Acanthamoeba polyphaga mimivirus (APMV) was first isolated during a pneumonia outbreak in Bradford, England, and since its discovery many research groups devoted efforts to understand whether this virus could be associated to human diseases, in particular clinical signs and symptoms of pneumonia. In 2013, we observed cytopathic effect in amoebas (rounding and lysis) inoculated with APMV inoculated PBMCs (peripheral blood mononuclear cell) extracts, and at that point we interpreted those results as mimivirus replication in human PBMCs. Based on these results we decided to further investigate APMV replication in human PBMCs, by transmission electron microscopy (TEM) and qPCR. No viral fac…
Topical Voriconazole as Supplemental Treatment for Acanthamoeba Keratitis
2020
Purpose Voriconazole was shown to inhibit ergosterol synthesis in various acanthamoeba species. The purpose of this study was to evaluate the clinical outcome of treatment with supplemental topical voriconazole in patients with acanthamoeba keratitis (AK). Methods All patients who had been treated for AK with voriconazole 1% drops in conjunction with topical first-line antiacanthamoeba therapy composed of polyhexamethylene biguanide (PHMB) 0.02% and propamidine isethionate 0.1% (Brolene) between November 2014 and August 2017 at the Department of Ophthalmology, University Medical Center Mainz, were included. The main outcomes were treatment failure and recurrence rate. Secondary outcomes wer…
Presence of potentially pathogenic free-living amoebae strains from well water samples in Guinea-Bissau
2014
Free-living amoebae (FLA) include opportunistic pathogens such as Naegleria fowleri, Balamuthia mandrillaris, and the genera Sappinia and Acanthamoeba. In this study, a survey was conducted in order to evaluate the presence of potentially pathogenic amoebic strains in water samples collected from wells located in the western part of Guinea-Bissau. The samples were left to precipitate for 48 hours and then the sediments were seeded on non-nutrient agar plates containing Escherichia coli spread and cultures were checked daily for the presence of FLA. Identification of FLA strains was based on the morphological and polymerase chain reaction (PCR) using the 18S rDNA or 16S mitochondrial rDNA ge…
Top-down effects of a lytic bacteriophage and protozoa on bacteria in aqueous and biofilm phases
2014
Lytic bacteriophages and protozoan predators are the major causes of bacterial mortality in natural microbial communities, which also makes them potential candidates for biological control of bacterial pathogens. However, little is known about the relative impact of bacteriophages and protozoa on the dynamics of bacterial biomass in aqueous and biofilm phases. Here, we studied the temporal and spatial dynamics of bacterial biomass in a microcosm experiment where opportunistic pathogenic bacteria Serratia marcescens was exposed to particle‐feeding ciliates, surface‐feeding amoebas, and lytic bacteriophages for 8 weeks, ca. 1300 generations. We found that ciliates were the most efficient enem…
Coincidental loss of bacterial virulence in multi-enemy microbial communities.
2014
The coincidental virulence evolution hypothesis suggests that outside-host selection, such as predation, parasitism and resource competition can indirectly affect the virulence of environmentally-growing bacterial pathogens. While there are some examples of coincidental environmental selection for virulence, it is also possible that the resource acquisition and enemy defence is selecting against it. To test these ideas we conducted an evolutionary experiment by exposing the opportunistic pathogen bacterium Serratia marcescens to the particle-feeding ciliate Tetrahymena thermophila, the surfacefeeding amoeba Acanthamoeba castellanii, and the lytic bacteriophage Semad11, in all possible combi…
Acanthamoeba isolates belonging to T1, T2, T3, T4 and T7 genotypes from environmental freshwater samples in the Nile Delta region, Egypt.
2006
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 speci…
Binding to complement factors and activation of the alternative pathway by Acanthamoeba.
2010
Acanthamoeba can cause severe ocular and cerebral diseases in healthy and immunocompromised individuals, respectively. Activation of complement appears to play an important role in host defence against infection. The exact mechanism, however, is still unclear. The aim of the present study was to investigate the effect of normal human serum (NHS) and normal mouse serum (NMS) on Acanthamoeba trophozoites, the binding of different complement factors to Acanthamoeba and the activation of the complement system. Moreover, we aimed to work out any possible differences between different strains of Acanthamoeba. A virulent T4 strain, a non-virulent T4 strain and a virulent T6 strain were included in…
Early Diagnosis of Acanthamoeba Infection during Routine Cytological Examination of Cerebrospinal Fluid
2006
ABSTRACT Early identification of Acanthamoeba in cerebrospinal fluid is mandatory to prevent fatal granulomatous amebic encephalitis. In the case presented here amebic trophozoites were detected in a routine cerebrospinal fluid sample. The antibiotic treatment and the apparently low virulence of this isolate were responsible for the benign progression of the infection.