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Govinda S. Visvesvara - One of the best experts on this subject based on the ideXlab platform.
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Molecular Confirmation of Sappinia pedata as a Causative Agent of Amoebic
2016Co-Authors: Yvonne Qvarnstrom, Frederick L. Schuster, Benjamin B. Gelman, Re J. Da Silva, Govinda S. VisvesvaraAbstract:(See the editorial commentary by Marciano-Cabral, on pages 1104–6.) Pathogenic free-living amoebae, such as Acanthamoeba spe-cies, Balamuthia mandrillaris, and Naegleria fowleri, are known to cause infections of the central nervous system in hu-man and other animals. In 2001, a case of human encephalitis was reported that was caused by another amoeba with mor-phological features suggestive of Sappinia. The amoeba origi-nally identified as Sappinia diploidea was identified, most likely as S. pedata, by use of newly developed real-time poly-merase chain reaction assays. This amoeba had previously been found only in environmental sources, such as soil and tree bark. The results illustrate the potential for other free-living amoebae, which are not normally associated with hu-man disease, to cause occasional infections. Free-living amoebae are ubiquitous in the environment world
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Infections with free-living amebae.
Handbook of Clinical Neurology, 2013Co-Authors: Govinda S. VisvesvaraAbstract:Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria fowleri are mitochondria-bearing, free-living eukaryotic amebae that have been known to cause infections of the central nervous system (CNS) of humans and other animals. Several species of Acanthamoeba belonging to several different genotypes cause an insidious and chronic disease, granulomatous amebic encephalitis (GAE), principally in immunocompromised hosts including persons infected with HIV/AIDS. Acanthamoeba spp., belonging to mostly group 2, also cause infection of the human cornea, Acanthamoeba keratitis. Balamuthia mandrillaris causes GAE in both immunocompromised and immunocompetent hosts mostly in the very young or very old individuals. Both Acanthamoeba spp. and B. mandrillaris also cause a disseminated disease including the lungs, skin, kidneys, and uterus. Naegleria fowleri, on the other hand, causes an acute and fulminating, necrotizing infection of the CNS called primary amebic meningoencephalitis (PAM) in children and young adults with a history of recent exposure to warm fresh water. Additionally, another free-living ameba Sappinia pedata, previously described as S. diploidea, also has caused a single case of amebic meningoencephalitis. In this review the biology of these amebae, clinical manifestations, molecular and immunological diagnosis, and epidemiological features associated with GAE and PAM are discussed.
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Amebic Meningoencephalitis and Keratitis
2011Co-Authors: Govinda S. Visvesvara, A J Martinez, Mary K. Klassen-fischer, Ronald C. NeafieAbstract:Abstract : Free-living amebae of the genera Naegleria, Acanthamoeba, and Balamuthia cause fatal diseases of the central nervous system (CNS) of humans.1-33 Naegleria fowleri causes an acute and fulminant primary amebic meningoencephalitis (PAM) in children and young adults with a history of exposure to fresh water leading to death within 5 to 10 days after the onset of symptoms.4-6,9,10,16,17,19,25,27,30,31,33,34 Balamuthia mandrillaris,2,3,7,8,19-22,24,26,28-31,35,36 and several species of Acanthamoeba (Acanthamoeba castellanii, Acanthamoeba culbertsoni, Acanthamoeba rhysodes, Acanthamoeba polyphaga, Acanthamoeba divionensis, Acanthamoeba healyi, and Acanthamoeba lenticulata) cause a chronic, and usually fatal, granulomatous amebic encephalitis (GAE) that may last for several weeks or months.1, 11,18,19,23,30,31,37-42 Acanthamoeba sp also cause an eyesight threatening infection, acanthamoeba keratitis, in humans, especially in persons wearing contact lenses.12,15,17,19,30,31,40,43-52 Additionally, N. fowleri, Acanthamoeba sp, and B. mandrillaris also infect animals.12-17, 19,28-31, 53-58 Sappinia diploidea, another freeliving ameba identified in 200159 as an agent of meningitis, was reidentified recently as Sappinia pedata based on molecular analysis.60 So far there is only one case reported due to this ameba.
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Molecular Confirmation of Sappinia pedata as a Causative Agent of Amoebic Encephalitis
The Journal of Infectious Diseases, 2009Co-Authors: Yvonne Qvarnstrom, Alexandre J. Da Silva, Frederick L. Schuster, Benjamin B. Gelman, Govinda S. VisvesvaraAbstract:Pathogenic free-living amoebae, such as Acanthamoeba species, Balamuthia mandrillaris, and Naegleria fowleri, are known to cause infections of the central nervous system in human and other animals. In 2001, a case of human encephalitis was reported that was caused by another amoeba with morphological features suggestive of Sappinia. The amoeba originally identified as Sappinia diploidea was identified, most likely as S. pedata, by use of newly developed real-time polymerase chain reaction assays. This amoeba had previously been found only in environmental sources, such as soil and tree bark. The results illustrate the potential for other free-living amoebae, which are not normally associated with human disease, to cause occasional infections.
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pathogenic and opportunistic free living amoebae acanthamoeba spp balamuthia mandrillaris naegleria fowleri and Sappinia diploidea
Fems Immunology and Medical Microbiology, 2007Co-Authors: Govinda S. Visvesvara, Hercules Moura, Frederick L. SchusterAbstract:Among the many genera of free-living amoebae that exist in nature, members of only four genera have an association with human disease: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri and Sappinia diploidea. Acanthamoeba spp. and B. mandrillaris are opportunistic pathogens causing infections of the central nervous system, lungs, sinuses and skin, mostly in immunocompromised humans. Balamuthia is also associated with disease in immunocompetent children, and Acanthamoeba spp. cause a sight-threatening infection, Acanthamoeba keratitis, mostly in contact-lens wearers. Of more than 30 species of Naegleria, only one species, N. fowleri, causes an acute and fulminating meningoencephalitis in immunocompetent children and young adults. In addition to human infections, Acanthamoeba, Balamuthia and Naegleria can cause central nervous system infections in animals. Because only one human case of encephalitis caused by Sappinia diploidea is known, generalizations about the organism as an agent of disease are premature. In this review we summarize what is known of these free-living amoebae, focusing on their biology, ecology, types of disease and diagnostic methods. We also discuss the clinical profiles, mechanisms of pathogenesis, pathophysiology, immunology, antimicrobial sensitivity and molecular characteristics of these amoebae.
Julia Walochnik - One of the best experts on this subject based on the ideXlab platform.
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Identification of free-living amoebae isolated from tap water in Istanbul, Turkey.
Experimental Parasitology, 2018Co-Authors: Miray Üstüntürk-onan, Julia WalochnikAbstract:Free-living amoebae (FLA) are widely spread in the environment and also known to cause rare but often serious infections. The present work focuses on a local survey on FLA. It is essential to know the prevalence and distribution of these microorganisms in order to get infections caused by them under control. In this study, FLA isolated from domestic tap water samples from homes of contact lens wearers were identified by morphology and by 18S rRNA gene sequence analysis. Morphological analysis and partial sequencing of the 18S rDNA revealed the presence of Acanthamoeba genotype T4 and Vermamoeba vermiformis in the investigated tap water samples. Naegleria fowleri, Balamuthia mandrillaris, and Sappinia spp. were not detected during this study. It was shown that species of FLA known to cause eye infections in humans are widely distributed in tap water in Istanbul, Turkey. Contact lens wearers should be aware of the risk of contamination from tap water and strictly apply stringent contact lens hygiene. With this study, we established Acanthamoeba genotype T4 and Vermamoeba vermiformis as contaminants of tap water in Istanbul.
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Molecular identification of bacterial endosymbionts of Sappinia strains
Parasitology Research, 2017Co-Authors: Daniele Corsaro, Julia Walochnik, Claudia Wylezich, Danielle Venditti, Rolf MichelAbstract:The genus Sappinia comprises free-living amoebae occurring worldwide in a variety of habitats such as soils, plant matter and freshwater ponds, but also animal faeces, and includes at present three species, S. pedata , S. diploidea and S. platani . The genus is potentially pathogenic, as indicated by the identification of S. pedata in a case of human amoebic encephalitis. Electron microscopy studies on some strains already revealed intracellular bacteria in Sappinia . In the current study, we performed 16S ribosomal RNA gene (rDNA) analysis of these bacterial endosymbionts. We first inferred relationships among Sappinia strains on the basis of 18S rDNA, demonstrating that S. pedata emerged as sister to a larger clade including S. diploidea , S. platani and a few ‘ S. diploidea -like’ strains. Thus, bacterial 16S rDNA was searched for in representative strains of each Sappinia species/subgroup. We found that Sappinia strains were associated to distinct species of Flavobacterium or Pedobacter (phylum Bacteroidetes ). These appear to be distributed following the amoebal host subgroups, and are not directly related to other Bacteroidetes species known as interacting with free-living amoebae. While all the endosymbionts’ close relatives are known to grow on agar, bacteriological media inoculated with amoebal extracts remained negative. Overall, results indicate that the recovered bacteria are likely specific obligate endosymbionts of Sappinia species. Further studies, including additional amoebal strains and deep morphological and molecular analyses, will be necessary to confirm this hypothesis.
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Acanthamoeba and other free-living amoebae in bat guano, an extreme habitat
Parasitology Research, 2016Co-Authors: Janez Mulec, Elisabeth Dietersdorfer, Miray Üstüntürk-onan, Julia WalochnikAbstract:Several representatives of the so-called free-living amoebae (FLA) are of medical relevance, not only as facultative pathogens but also as vehicles for pathogenic bacteria. Some FLA can survive and even grow under extreme environmental conditions. Bat guano is an exceptional habitat, the conditions becoming gradually more extreme with aging. In the current study, samples of bat guano of different ages from five caves in Slovenia were screened for the presence of FLA. FLA were isolated from almost all guano samples, including guano with a pH of 3.5. Only the two samples that had been drawn from >20-year-old guano were negative for FLA. Generally, FLA diversity correlated to high concentrations of cultivable bacteria (∼10^8 CFU/g) and fungi (∼10^5 CFU/g). Interestingly, the absence of FLA in seasoned guanos was mirrored by the presence of dictyostelid slime moulds. The isolated amoebae were identified as belonging to the genera Acanthamoeba , Copromyxa , Naegleria , Sappinia , Tetramitus , Thecamoeba , Vahlkampfia , Vannella and Vermamoeba . To the best of our knowledge, this is the first study on the diversity of FLA in guano.
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Electron Microscopical Investigations of a New Species of the Genus Sappinia (Thecamoebidae, Amoebozoa), Sappinia platani sp. nov., Reveal a Dictyosome in this Genus
Acta Protozoologica, 2014Co-Authors: Claudia Wylezich, Rolf Michel, Daniele Corsaro, Alexander Kudryavtsev, Julia WalochnikAbstract:The genus Sappinia belongs to the family Thecamoebidae within the Discosea (Amoebozoa). For long time the genus comprised only two species, S. pedata and S. diploidea, based on morphological investigations. However, recent molecular studies on gene sequences of the small subunit ribosomal RNA (SSU rRNA) gene revealed a high genetic diversity within the genus Sappinia. This indicated a larger species richness than previously assumed and the establishment of new species was predicted. Here, Sappinia platani sp. nov. (strain PL-247) is described and ultrastructurally investigated. This strain was isolated from the bark of a sycamore tree (Koblenz, Germany) like the re-described neotype of S. diploidea. The new species shows the typical characteristics of the genus such as flattened and binucleate trophozoites with a differentiation of anterior hyaloplasm and without discrete pseudopodia as well as bicellular cysts. Additionally, the new species possesses numerous endocytobionts and dictyosomes. The latter could not be found in previous EM studies of the genus Sappinia. Standing forms, a character of the species S. pedata, could be formed on older cultures of the new species but appeared extremely seldom. A loose layer of irregular, bent hair-like structures cover the plasma membrane dissimilar to the glycocalyx types as formerly detected in other Sappinia strains.
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The genus Sappinia: history, phylogeny and medical relevance.
Experimental Parasitology, 2009Co-Authors: Julia Walochnik, Claudia Wylezich, Rolf MichelAbstract:The genus Sappinia with the single species Sappinia pedata was established for an amoeba with two nuclei and pedicellate "cysts" by Dangeard in 1896. In 1912, Alexeieff transferred an also double nucleated, but apparently sexually reproducing amoeba to this genus as Sappinia diploidea, that had been described as Amoeba diploidea by Hartmann and Nagler in 1908. As the original isolates were lost, Michel and colleagues established a neotype for S. diploidea in 2006 and Brown and colleagues established a neotype for S. pedata in 2007. Molecular analyses have corroborated the differentiation between S. pedata and S. diploidea, however, the genus splits into more than two well separated clusters. Altogether, the genus Sappinia is now classified as a member of the Thecamoebidae and, moreover, as potentially pathogenic. In 2001, Gelman and colleagues reported a case of severe encephalitis in a non-immunocompromised young man caused by Sappinia.
Rolf Michel - One of the best experts on this subject based on the ideXlab platform.
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Molecular identification of bacterial endosymbionts of Sappinia strains
Parasitology Research, 2017Co-Authors: Daniele Corsaro, Julia Walochnik, Claudia Wylezich, Danielle Venditti, Rolf MichelAbstract:The genus Sappinia comprises free-living amoebae occurring worldwide in a variety of habitats such as soils, plant matter and freshwater ponds, but also animal faeces, and includes at present three species, S. pedata , S. diploidea and S. platani . The genus is potentially pathogenic, as indicated by the identification of S. pedata in a case of human amoebic encephalitis. Electron microscopy studies on some strains already revealed intracellular bacteria in Sappinia . In the current study, we performed 16S ribosomal RNA gene (rDNA) analysis of these bacterial endosymbionts. We first inferred relationships among Sappinia strains on the basis of 18S rDNA, demonstrating that S. pedata emerged as sister to a larger clade including S. diploidea , S. platani and a few ‘ S. diploidea -like’ strains. Thus, bacterial 16S rDNA was searched for in representative strains of each Sappinia species/subgroup. We found that Sappinia strains were associated to distinct species of Flavobacterium or Pedobacter (phylum Bacteroidetes ). These appear to be distributed following the amoebal host subgroups, and are not directly related to other Bacteroidetes species known as interacting with free-living amoebae. While all the endosymbionts’ close relatives are known to grow on agar, bacteriological media inoculated with amoebal extracts remained negative. Overall, results indicate that the recovered bacteria are likely specific obligate endosymbionts of Sappinia species. Further studies, including additional amoebal strains and deep morphological and molecular analyses, will be necessary to confirm this hypothesis.
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Electron Microscopical Investigations of a New Species of the Genus Sappinia (Thecamoebidae, Amoebozoa), Sappinia platani sp. nov., Reveal a Dictyosome in this Genus
Acta Protozoologica, 2014Co-Authors: Claudia Wylezich, Rolf Michel, Daniele Corsaro, Alexander Kudryavtsev, Julia WalochnikAbstract:The genus Sappinia belongs to the family Thecamoebidae within the Discosea (Amoebozoa). For long time the genus comprised only two species, S. pedata and S. diploidea, based on morphological investigations. However, recent molecular studies on gene sequences of the small subunit ribosomal RNA (SSU rRNA) gene revealed a high genetic diversity within the genus Sappinia. This indicated a larger species richness than previously assumed and the establishment of new species was predicted. Here, Sappinia platani sp. nov. (strain PL-247) is described and ultrastructurally investigated. This strain was isolated from the bark of a sycamore tree (Koblenz, Germany) like the re-described neotype of S. diploidea. The new species shows the typical characteristics of the genus such as flattened and binucleate trophozoites with a differentiation of anterior hyaloplasm and without discrete pseudopodia as well as bicellular cysts. Additionally, the new species possesses numerous endocytobionts and dictyosomes. The latter could not be found in previous EM studies of the genus Sappinia. Standing forms, a character of the species S. pedata, could be formed on older cultures of the new species but appeared extremely seldom. A loose layer of irregular, bent hair-like structures cover the plasma membrane dissimilar to the glycocalyx types as formerly detected in other Sappinia strains.
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The genus Sappinia: history, phylogeny and medical relevance.
Experimental Parasitology, 2009Co-Authors: Julia Walochnik, Claudia Wylezich, Rolf MichelAbstract:The genus Sappinia with the single species Sappinia pedata was established for an amoeba with two nuclei and pedicellate "cysts" by Dangeard in 1896. In 1912, Alexeieff transferred an also double nucleated, but apparently sexually reproducing amoeba to this genus as Sappinia diploidea, that had been described as Amoeba diploidea by Hartmann and Nagler in 1908. As the original isolates were lost, Michel and colleagues established a neotype for S. diploidea in 2006 and Brown and colleagues established a neotype for S. pedata in 2007. Molecular analyses have corroborated the differentiation between S. pedata and S. diploidea, however, the genus splits into more than two well separated clusters. Altogether, the genus Sappinia is now classified as a member of the Thecamoebidae and, moreover, as potentially pathogenic. In 2001, Gelman and colleagues reported a case of severe encephalitis in a non-immunocompromised young man caused by Sappinia.
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High genetic diversity of Sappinia-like strains (Amoebozoa, Thecamoebidae) revealed by SSU rRNA investigations.
Parasitology Research, 2009Co-Authors: Claudia Wylezich, Julia Walochnik, Rolf MichelAbstract:Sappinia diploidea is known as a free-living amoeba of worldwide distribution and has also been reported as causative agent of a brain infection in an immunocompetent young man. In the current study, we were able to isolate eight strains of S. diploidea-like amoebae identified by light microscopy from different habitats. Cultures of all strains were established successfully for molecular characterization. The small subunit ribosomal RNA genes of all strains were sequenced and compared to one another, to the neotype of S. diploidea, and to strains of Sappinia pedata, the only other Sappinia species known to date, from GenBank by multiple sequence alignment and cluster analysis. Altogether, the phylogenetic position of the genus Sappinia within the Thecamoebidae was corroborated; however, it was shown that the genus splits into several well-separated clusters making the establishment of new species within this genus inevitable. Furthermore, two of the S. diploidea-like strains were actually more closely related to S. pedata than to S. diploidea, although the diagnostically relevant standing form which seems to be characteristic for S. pedata was not observed in either of the two strains.
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isolation of the amoeba thecamoeba quadrilineata harbouring intranuclear spore forming endoparasites considered as fungus like organisms
Acta Protozoologica, 2009Co-Authors: Rolf Michel, Barbel Hauroder, Lothar ZollerAbstract:Among a population of Thecamoeba quadrilineata (Thecamoebidae) isolated from moss samples some trophozoites harboured intracellular aggregates of round-oval parasites which turned out to be spores with a real nucleus. These organisms were supposed to be fungal endoparasites beginning their development within the nucleus of the host invaded by young parasitic stages after the host amoeba had engulfed free spores from the environment. The complete developmental cycle was studied by electron microscopy, showing the intranuclear growth of freshly invaded young stages into large spore forming parasites differentiating into a great number of spores - all within the border of the host's nuclear membrane. These spores were not released into the environment until the death and decay of the host amoeba, where they could be ingested as infective stages by hitherto not infected thecamoebae. Host range studies with various free-living amoebae (FLA) showed that T striata and T. terricola were as permissive to infection as the original host T. quadrilineata. Sappinia was only susceptible to a certain extent and therefore not considered as possible natural host. Remarkably, this observation shows that both nuclei of the bi-nucleate amoeba became simultaneously infected. The present morphological description corresponds to early observations with fungal intranuclear parasites called Nucleophaga Dangeard, 1887. However, genetic and phylogenetic studies have to corroborate the supposed fungal nature.
Frederick L. Schuster - One of the best experts on this subject based on the ideXlab platform.
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Molecular Confirmation of Sappinia pedata as a Causative Agent of Amoebic
2016Co-Authors: Yvonne Qvarnstrom, Frederick L. Schuster, Benjamin B. Gelman, Re J. Da Silva, Govinda S. VisvesvaraAbstract:(See the editorial commentary by Marciano-Cabral, on pages 1104–6.) Pathogenic free-living amoebae, such as Acanthamoeba spe-cies, Balamuthia mandrillaris, and Naegleria fowleri, are known to cause infections of the central nervous system in hu-man and other animals. In 2001, a case of human encephalitis was reported that was caused by another amoeba with mor-phological features suggestive of Sappinia. The amoeba origi-nally identified as Sappinia diploidea was identified, most likely as S. pedata, by use of newly developed real-time poly-merase chain reaction assays. This amoeba had previously been found only in environmental sources, such as soil and tree bark. The results illustrate the potential for other free-living amoebae, which are not normally associated with hu-man disease, to cause occasional infections. Free-living amoebae are ubiquitous in the environment world
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Molecular Confirmation of Sappinia pedata as a Causative Agent of Amoebic Encephalitis
The Journal of Infectious Diseases, 2009Co-Authors: Yvonne Qvarnstrom, Alexandre J. Da Silva, Frederick L. Schuster, Benjamin B. Gelman, Govinda S. VisvesvaraAbstract:Pathogenic free-living amoebae, such as Acanthamoeba species, Balamuthia mandrillaris, and Naegleria fowleri, are known to cause infections of the central nervous system in human and other animals. In 2001, a case of human encephalitis was reported that was caused by another amoeba with morphological features suggestive of Sappinia. The amoeba originally identified as Sappinia diploidea was identified, most likely as S. pedata, by use of newly developed real-time polymerase chain reaction assays. This amoeba had previously been found only in environmental sources, such as soil and tree bark. The results illustrate the potential for other free-living amoebae, which are not normally associated with human disease, to cause occasional infections.
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pathogenic and opportunistic free living amoebae acanthamoeba spp balamuthia mandrillaris naegleria fowleri and Sappinia diploidea
Fems Immunology and Medical Microbiology, 2007Co-Authors: Govinda S. Visvesvara, Hercules Moura, Frederick L. SchusterAbstract:Among the many genera of free-living amoebae that exist in nature, members of only four genera have an association with human disease: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri and Sappinia diploidea. Acanthamoeba spp. and B. mandrillaris are opportunistic pathogens causing infections of the central nervous system, lungs, sinuses and skin, mostly in immunocompromised humans. Balamuthia is also associated with disease in immunocompetent children, and Acanthamoeba spp. cause a sight-threatening infection, Acanthamoeba keratitis, mostly in contact-lens wearers. Of more than 30 species of Naegleria, only one species, N. fowleri, causes an acute and fulminating meningoencephalitis in immunocompetent children and young adults. In addition to human infections, Acanthamoeba, Balamuthia and Naegleria can cause central nervous system infections in animals. Because only one human case of encephalitis caused by Sappinia diploidea is known, generalizations about the organism as an agent of disease are premature. In this review we summarize what is known of these free-living amoebae, focusing on their biology, ecology, types of disease and diagnostic methods. We also discuss the clinical profiles, mechanisms of pathogenesis, pathophysiology, immunology, antimicrobial sensitivity and molecular characteristics of these amoebae.
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Opportunistic amoebae: challenges in prophylaxis and treatment.
Drug Resistance Updates, 2004Co-Authors: Frederick L. Schuster, Govinda S. VisvesvaraAbstract:This review focuses on free-living amoebae, widely distributed in soil and water, causing opportunistic and non-opportunistic infections in humans: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea. Diseases include primary amoebic meningoencephalitis (N. fowleri), granulomatous amoebic encephalitis, cutaneous and nasopharyngeal infections (Acanthamoeba spp., Balamuthia mandrillaris, S. diploidea), and amoebic keratitis (Acanthamoeba spp). Acanthamoeba, Balamuthia, and Naegleria have been repeatedly isolated; S. diploidea has been reported only once, from a brain infection. Antimicrobial therapy for these infections is generally empirical and patient recovery often problematic. N. fowleri is highly sensitive to the antifungal agent amphotericin B, but delay in diagnosis and the fulminant nature of the disease result in few survivors. Encephalitis and other infections caused by Acanthamoeba and Balamuthia have been treated, more or less successfully, with antimicrobial combinations including sterol-targeting azoles (clotrimazole, miconazole, ketoconazole, fluconazole, itraconazole), pentamidine isethionate, 5-fluorocytosine, and sulfadiazine. The use of drug combinations addresses resistance patterns that may exist or develop during treatment, ensuring that at least one of the drugs may be effective against the amoebae. Favorable drug interactions (additive or synergistic) are another potential benefit. In vitro drug testing of clinical isolates points up strain and species differences in sensitivity, so that no single drug can be assumed effective against all amoebae. Another complication is risk of activation of dormant cysts that form in situ in Acanthamoeba and Balamuthia infections, and which can lead to patient relapse following apparently effective treatment. This is particularly true in Acanthamoeba keratitis, a non-opportunistic infection of the cornea, which responds well to treatment with chlorhexidine gluconate and polyhexamethylene biguanide, in combination with propamidine isothionate (Brolene), hexamidine (Desomodine), or neomycin. Acanthamoeba spp. may also be carriers of endosymbiotic bacteria (Legionella and Legionella-like pathogens) and have been implicated in outbreaks of pneumonias in debilitated hosts. As with other infectious diseases, recovery is dependent not only on antimicrobial therapy, but also on patient's immune status, infective dose and virulence of the ameba strain, and on how early the disease is diagnosed and drug therapy initiated.
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Cultivation of pathogenic and opportunistic free-living amebas.
Clinical Microbiology Reviews, 2002Co-Authors: Frederick L. SchusterAbstract:Free-living amebas are widely distributed in soil and water, particularly members of the genera Acanthamoeba and Naegleria. Since the early 1960s, they have been recognized as opportunistic human pathogens, capable of causing infections of the central nervous system (CNS) in both immunocompetent and immunocompromised hosts. Naegleria is the causal agent of a fulminant CNS condition, primary amebic meningoencephalitis; Acanthamoeba is responsible for a more chronic and insidious infection of the CNS termed granulomatous amebic encephalitis, as well as amebic keratitis. Balamuthia sp. has been recognized in the past decade as another ameba implicated in CNS infections. Cultivation of these organisms in vitro provides the basis for a better understanding of the biology of these amebas, as well as an important means of isolating and identifying them from clinical samples. Naegleria and Acanthamoeba can be cultured axenically in cell-free media or on tissue culture cells as feeder layers and in cultures with bacteria as a food source. Balamuthia, which has yet to be isolated from the environment, will not grow on bacteria. Instead, it requires tissue culture cells as feeder layers or an enriched cell-free medium. The recent identification of another ameba, Sappinia diploidea, suggests that other free-living forms may also be involved as causal agents of human infections.
Jeffrey D Silberman - One of the best experts on this subject based on the ideXlab platform.
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Amoeba at attention: Phylogenetic affinity of Sappinia pedata
Journal of Eukaryotic Microbiology, 2007Co-Authors: Matthew W Brown, Frederick W Spiegel, Jeffrey D SilbermanAbstract:The genus Sappinia, a taxon of free-living amoebae with trophozoites that typically have two closely appressed nuclei, contains two named species, Sappinia pedata, the type species, and S. diploidea. The amoebae of both species are essentially identical according to the literature. The two species are distinguished by S. pedata having a standing amoeba stage, incorrectly interpreted as a cyst, and S. diploidea having sessile, bicellular cysts. Using four isolates of S. pedata collected from around the world, we present detailed light micrographic illustrations of all stages of its life cycle. We confirm that the standing amoeba lacks a cell wall. In two isolates of S. pedata, there are bicellular cysts indistinguishable from those of S. diploidea. Using sequence data from the nuclear small subunit ribosomal RNA gene, we conclude that S. pedata and the published neotype of S. diploidea are congeneric but not conspecific. The genus branches within Thecamoebidae. Sequencing of the actin gene confirms the inclusion of Sappinia in Thecamoebidae. Resolving the taxonomy of Sappinia is gaining importance because it has recently been attributed as an opportunistic human pathogen.
