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PubMed1993

Pathogenic and free-living amoebae isolated from swimming pools and physiotherapy tubs in Mexico.

A protozoological survey was done to isolate free-living amoebae from swimming pools and physiotherapy tubs in Mexico City. Amoebae were isolated by culture in nonnutritive agar medium combined with Escherichia coli. Identification of the isolates was done by morphology using specialized taxonomic keys and by isoelectric focusing of total proteins and isoenzymes in agarose. Pathogenicity of the isolates was determined in 3-week-old mice by intracerebral and intranasal inoculations. Statistical tools were used to determine the existence of significant differences on the incidence and diversity of the isolates in relation to the two types of water bodies analyzed. Water and environmental temperatures, pH, and chloride concentrations were determined at each sampling site. Twenty-nine amoebic strains from eight genera were isolated. Most frequently found were specimens of the genera (Acanthamoeba (with four pathogenic strains), Vahlkampfia, Hartmannella, and Naegleria. Amoebae were isolated more frequently in spring and summer, and could not be recovered from pools with chloride levels of 5.31 mg/ml or more. This survey demonstrates that chloride concentrations commonly used in recreative pools and therapy tubs are not sufficient to eliminate viable cysts of most free-living amoebae. Significantly higher numbers of isolates were retrieved from the pools than from the tubs.

Amebiasis↗
PubMed1999

Primary and secondary structure of the small-subunit ribosomal RNA of the naked, marine amoeba Vannella anglica: phylogenetic implications.

The primary and secondary structure of the small-subunit ribosomal RNA (ssrRNA) gene from the naked, marine amoeba, Vannella anglica (subclass Gymnamoebia), was determined. The ssrRNA is 1962 nucleotides in length, with a low G+C content of 37.1%. The ssrRNA is composed of several uncommon secondary structure features including helix E8-1, which may be a useful target for rRNA probes for the direct identification of isolates in mixed culture. Phylogenetic analysis of sequence data showed that V. anglica branched prior to the rapid diversification of the eukaryotes. It did not associate with the other naked, lobose amoebae represented by Acanthamoeba and Hartmannella, indicating that Vannella represents a separate amoeboid lineage and the subclass Gymnamoebia is polyphyletic.

Amino Acid Sequence↗
PubMed2005

Seasonal changes in free-living amoeba species in the root canopy of Zygophyllum dumosum in the Negev Desert, Israel.

The influence of seasonality and Zygophyllum dumosum root canopy on the species diversity of free-living amoebae at two soil depths (0-10 and 10-20 cm) was studied in a Negev Desert ecosystem in Israel. Free-living amoebae were extracted and identified after cultivation in non-nutritive agar plates. A total of 90 amoeba species were identified in the soil during the study period, with the most common genera present being Hartmannella, Platyamoeba, Vahlkampfia, Acanthamoeba, and Echinamoeba. Differences between the control soil and the soil under Z. dumosum were found mainly during the dry seasons, when 97% similarity was found between the two soil layers, which could be due to the effect of the shrub on the soil microenvironment. The amoeba community exhibited more species diversity in spring (reaching a value of 34 species) than in the winter (18 species) or summer and autumn (20 species), since the community has a time lag for becoming stabilized after the dry summer and autumn. This is one of the first studies on the amoeba population in the Negev Desert and elucidates the importance and the need for taking trophic and functional groups into consideration in order to understand biomineralization processes.

Amoebida↗
PubMed2002

Distribution of free-living amoebae in James River, Virginia, USA.

A comprehensive survey to document the presence of free-living amoebae was conducted along 58 km of James River, near Richmond, Virginia, USA. Sites included tidal and non-tidal freshwater areas, near 40 combined sewer outflows, three municipal wastewater treatment plant release sites, and thermal discharge from a coal-fired power plant. Amoebae were present on all collection dates, spring through autumn, and at all sites ( n=330). Five genera, Naegleria, Vannella, Acanthamoeba, Vahlkampfia, and Hartmannella were present in both the water column and sediment. The most common isolates from the water column were Naegleria and Vannella. Water conditions conducive to the presence of large quantities of fecal coliform bacteria were correlated with the prevalence of free-living amoebae. Some of the amoebae in this complex ecosystem can act as opportunistic pathogens, may play a role in diseases of aquatic organisms in this heavily urbanized river, and may present a risk to human health.

Animals↗
PubMed2000

Vannella sp. harboring Microsporidia-like organisms isolated from the contact lens and inflamed eye of a female keratitis patient.

Viable Hartmannella sp. and two strains of Vannella sp.--but no Acanthamoebae--multiplied on NN-agar inoculated with pieces of the contact lens from a female keratitis patient. Within the cytoplasm of one Vannella isolate, intracellular parasites could be observed whose earliest stages were developing within the nucleus, resembling those Microsporidia-like parasites seen within Vannella isolated recently from a warm tapwater system. This assumption was also confirmed by electron microscopy. In swabs taken directly from the cornea, Pseudomonas aeruginosa were identified, but they did not yield any growth of amebas in culture. However, cocultivation of parasite-free Vannella strains with the above-mentioned swab matter resulted in infected amebas harboring the same intracellular parasites seen before. This infection could be established only if the corresponding spores were present as infective agents in the swab matter. The successful treatment of the patient with antibiotics supports the assumption that P. aeruginosa was the main cause of the corneal ulceration. The extent to which the Microsporidia-like organisms may have been involved in the development of keratitis remains a matter of discussion.

Adult↗
PubMed2006

Microbial ecology of drinking water distribution systems.

The supply of clean drinking water is a major, and relatively recent, public health milestone. Control of microbial growth in drinking water distribution systems, often achieved through the addition of disinfectants, is essential to limiting waterborne illness, particularly in immunocompromised subpopulations. Recent inquiries into the microbial ecology of distribution systems have found that pathogen resistance to chlorination is affected by microbial community diversity and interspecies relationships. Research indicates that multispecies biofilms are generally more resistant to disinfection than single-species biofilms. Other recent findings are the increased survival of the bacterial pathogen Legionella pneumophila when present inside its protozoan host Hartmannella vermiformis and the depletion of chloramine disinfectant residuals by nitrifying bacteria, leading to increased overall microbial growth. Interactions such as these are unaccounted for in current disinfection models. An understanding of the microbial ecology of distribution systems is necessary to design innovative and effective control strategies that will ensure safe and high-quality drinking water.

Animals↗
PubMed2006

Resistance of different Chlamydia-like organisms to quinolones and mutations in the quinoline resistance-determining region of the DNA gyrase A- and topoisomerase-encoding genes.

Parachlamydia acanthamoebae has been shown to be resistant to fluoroquinolones. In this study, we determined the susceptibility of Neochlamydia hartmannellae and Simkania negevensis to quinolones using amoebal co-culture in the presence of serial dilutions of ciprofloxacin. The gyrA and parC quinoline resistance-determining regions (QRDRs) were amplified and sequenced, and amino acid substitutions that may explain the observed quinolone resistance were investigated. Neochlamydia and Simkania were resistant to 16 microg/mL ciprofloxacin. Substitution at positions 83 and 70 of GyrA QRDR were present in Neochlamydia and in both Parachlamydia strains studied. For Simkania, substitutions at positions 99 and 101 in the GyrA QRDR and at positions 81 and 84 in the ParC QRDR were observed. Resistance of Parachlamydia, Neochlamydia and Simkania to quinolones is likely due to these mutations.

Amino Acid Sequence↗
PubMed2001

The unusually long small subunit ribosomal RNA gene found in amitochondriate amoeboflagellate Pelomyxa palustris: its rRNA predicted secondary structure and phylogenetic implication.

In order to ascertain a phylogenetic position of the freshwater amitochondriate amoeboflagellate Pelomyxa palustris its small subunit (SSU) rRNA gene was amplified and sequenced. It was shown to be 3502 bp long. The predicted secondary structure of its rRNA includes at least 16 separate expansion zones located in all the variable regions (V1-V9), as well as in some conservative gene regions. Most insertions are represented by sequences of low complexity that have presumably arisen by a slippage mechanism. Relatively conservative, uniformly positioned motifs contained in regions V4 and V7, as well as in some others, made it possible to perform folding. In maximum likelihood, maximum parsimony, and neighbor-joining trees, P. palustris tends to cluster with amitochondriate and secondary lost mitochondria amoebae and amoeboflagellates Entamoeba, Endolimax nana, and Phreatamoeba balamuthi, comprising together with them and aerobic lobose amoebae Vannella, Acanthamoeba, Balamuthia, and Hartmannella a monophyletic cluster. Another pelobiont, Mastigamoeba invertens, does not belong to this cluster. No specific similarity was discovered between the SSU rRNA of P. palustris and amitochondriate taxa of 'Archezoa': Diplomonada, Parabasalia, Microsporidia. Pelomyxa palustris SSU rRNA does not occupy a basal position in the phylogenetic trees and could be ascribed to the so-called eukaryotic 'crown' group if the composition of the latter were not so sensitive to the methods of tree building. Thus, molecular and morphological data suggest that P. palustris represents a secondarily modified eukaryotic lineage.

Amoeba↗
PubMed2004

Preliminary report on the northern Australian melioidosis environmental surveillance project.

An environmental surveillance programme was developed to determine whether water supplies could be a source of Burkholderia pseudomallei as noted during previous melioidosis outbreak investigations. Water supplies to communities in the three northern Australian jurisdictions (Western Australia, Northern Territory and Queensland) were sampled periodically during 2001 and 2002. Water and soil samples were collected from communities known to have had recent culture-positive melioidosis cases and nearby communities where no cases had been diagnosed. Clinical isolates of B. pseudomallei obtained from northern Australian patients during 2001 and 2002 were compared with the environmental B. pseudomallei isolates by ribotyping and pulsed-field gel electrophoresis. B. pseudomallei was isolated from 11 distinct locations, all in the Northern Territory, seven of which were associated with culture-positive melioidosis cases (>1 case at three locations). Water was implicated as a possible environmental source of melioidosis in six locations. A variety of free-living amoebae including Acanthamoeba and Hartmannella spp. that are potential hosts to B. pseudomallei were recovered from environmental specimens. Culturable B. pseudomallei was not found to be widely dispersed in the environments sampled.

Animals↗
PubMed1984

[Amebic keratitis: clinico-histopathologic case report].

The present paper describes a case of amebic keratitis in a 63-year-old female patient, who had been wearing hard contact lenses to correct myopia. The clinical course was characterized by early superficial corneal infiltrates accompanied by a marked iritis and excruciating pain. Later a ring abscess developed, combined with a disciform infiltration of the deep central stroma and a recalcitrant superficial corneal ulcer. The disease ran a very chronic course over more than 3 months. After various conservative treatments including topical steroids, antibiotics, antimycotic, and antiviral drugs, a penetrating keratoplasty had to be performed. The histopathologic examination of the corneal button revealed many encysted amebas and a few trophozoites which were classified by direct immunofluorescence as belonging to the genus Acanthamoeba (Hartmannella). Six months after keratoplasty the eye was quit without any signs of recurrence. As far as the authors know, this is the first reported case of an amebic keratitis associated with contact lenses.

Amebiasis↗
PubMed1992

Legionella pneumophila mip gene potentiates intracellular infection of protozoa and human macrophages.

Legionella pneumophila is an intracellular parasite of freshwater protozoa and human macrophages. Recent studies determined that the macrophage infectivity potentiator (Mip) surface protein, a prokaryotic homolog of the FK506-binding proteins, is required for optimal infection of macrophages. To determine whether Mip is also involved in L. pneumophila infection of protozoa, we examined the ability of a strain lacking Mip to parasitize Hartmannella amoebae and Tetrahymena ciliates. After 3 days of incubation, approximately 1000-fold fewer bacteria were recovered from protozoan cocultures infected with the Mip- strain than from those cocultures infected with an isogenic Mip+ strain. The mip mutant was, however, not impaired in its ability to bind to amoebae cell surfaces, indicating that Mip is involved in bacterial resistance to intracellular killing and/or intracellular multiplication. These data suggest that L. pneumophila employs similar genes and mechanisms to infect human cells and protozoa. Furthermore, they support the hypothesis that the ability of L. pneumophila to parasitize macrophages and hence to cause human disease is a consequence of its prior adaptation to intracellular growth within protozoa.

Amoeba↗
PubMed1983

Recovery of soil amoebae from the air during the harmattan in Zaria, Nigeria.

An attempt was made to recover soil amoebae from the air during the harmattan in Zaria, Nigeria. Non-nutrient agar plates seeded with Escherichia coli were used as settle plates and exposed to the air for 30 minutes to four hours, after which they were incubated at 27 degrees C or at 37 degrees C. A total of 38 strains of amoebae were cultured: 21 of the genus Hartmannella, eight Naegleria, four Schizopyrenus, three Didascalus and two Tetramitus. Three pathogenic species, H. culbertsoni, N. fowleri and H. rhysodes, were also recovered and all killed mice. These results suggest the possibility of airborne primary amoebic meningoencephalitis infections in Nigeria.

Air Microbiology↗
PubMed1996

Quantitation of free-living amoebae and bacterial populations in eyewash stations relative to flushing frequency.

This study investigated the concentration of amoebic and bacterial populations in eyewash station water relative to various flushing regimens. Amoebae concentrations averaged approximately 200 amoebae/100 mL in 13 of 15 stations positive for amoebae and consisted of Hartmannella and Acanthamoeba. Bacterial concentrations ranged from 10(0) to more than 10(5) colony forming units per mL. Amoebic concentrations differed notably between stations located in Buildings X and Y (p < 0.0001). Further study indicated that removal of diffusing screens did not substantially change (p > 0.05) the concentration of amoeba. Amoebic and bacterial concentrations temporarily decreased with the various flushing regimens tested. Lower amoebic concentrations were not sustained by a weekly 3-minute or a monthly 1-minute flushing regimen. However, weekly 3-minute flushes appeared to be more effective in maintaining lowered bacterial concentrations (p < 0.0001).

Amoeba↗
PubMed2001

SSU rRNA-based phylogenetic position of the genera Amoeba and Chaos (Lobosea, Gymnamoebia): the origin of gymnamoebae revisited.

Naked lobose amoebae (gymnamoebae) are among the most abundant group of protists present in all aquatic and terrestrial biotopes. Yet, because of lack of informative morphological characters, the origin and evolutionary history of gymnamoebae are poorly known. The first molecular studies revealed multiple origins for the amoeboid lineages and an extraordinary diversity of amoebae species. Molecular data, however, exist only for a few species of the numerous taxa belonging to this group. Here, we present the small-subunit (SSU) rDNA sequences of four species of typical large gymnamoebae: Amoeba proteus, Amoeba leningradensis, Chaos nobile, and Chaos carolinense. Sequence analysis suggests that the four species are closely related to the species of genera Saccamoeba, Leptomyxa, Rhizamoeba, Paraflabellula, Hartmannella, and Echinamoeba. All of them form a relatively well-supported clade, which corresponds to the subclass Gymnamoebia, in agreement with morphology-based taxonomy. The other gymnamoebae cluster in small groups or branch separately. Their relationships change depending on the type of analysis and the model of nucleotide substitution. All gymnamoebae branch together in Neighbor-Joining analysis with corrections for among-site rate heterogeneity and proportion of invariable sites. This clade, however, is not statistically supported by SSU rRNA gene sequences and further analysis of protein sequence data will be necessary to test the monophyly of gymnamoebae.

Amoeba↗
PubMed1992

Isolation and characterization of a conjugative plasmid from Legionella pneumophila.

The conjugative properties of an indigenous 85 MDa plasmid (designated pCH1) from Legionella pneumophila were studied. To determine if pCH1 was transmissible by conjugation, mating experiments were performed between legionellae that harboured pCH1 and several plasmid-less recipients. Plasmid transfer was monitored by colony hybridization, using a cloned 21.0 kb SalI restriction fragment from pCH1 as a probe. The results from these experiments showed that pCH1 could be conjugatively transferred into several strains of L. pneumophila serogroup 1 but not into strain Bloomington-2 (serogroup 3) or Escherichia coli. Southern hybridization experiments in which pCH1 DNA was used as a probe showed that pCH1 does not share homology with other indigenous L. pneumophila plasmids. There was no detectable DNA homology between pCH1 and L. pneumophila chromosomal DNA. Additional mating experiments revealed that pCH1 was unable to mobilize the L. pneumophila chromosome. The conjugative transfer of pCH1 into plasmid-less avirulent or virulent serogroup 1 strains did not alter the intracellular growth characteristics of these strains in U937 cells, a human-monocyte-like cell line, or in the amoeba Hartmannella vermiformis. These results suggest that pCH1 does not contribute to the ability of L. pneumophila to enter or grow within eukaryotic cells.

Cloning, Molecular↗
PubMed1978

The occurrence of amphizoic Amebae in domestic animals.

Random examination of domestic animals revealed the frequent presence of free-living amebae in their bodies. In diseased or dead cows, dogs, pigs, rabbits, pigeons, and turkeys 15 strains of amebae were found, belonging to the genera Acanthamoeba (A. polyphaga), Hartmannella (H. vermiformis), and Vahlkampfia (V. avara, V. enterica, V. inornata). They were usually accompanied by other infectious agents in different parts of the host bodies. Pathogenicity of 3 isolates could not be demonstrated by inoculation of laboratory animals. Some features of the isolates differed from those previously known for members of these genera. These strains may be considered amphizoic amebae according to Page (1974).

Amebiasis↗
PubMed1986

Seasonal distribution of thermotolerant free-living amoebae. I. Willard's Pond.

A quantitative study of the seasonal distribution of thermotolerant (37 degrees C and 45 degrees C), small free-living amoebae (FLA) was conducted in Willard's Pond, a warm, monomictic lake in the Piedmont region of South Carolina. Correlation of physical and chemical parameters with the seasonal distribution was facilitated by partitioning the aquatic ecosystem into benthic, planktonic, and neustonic habitats. Population densities of FLA peaked in late summer in each habitat; however, species composition varied between habitats. Littoral sediment appeared to be the major habitat for FLA, with peaks in populations of Acanthamoeba and Naegleria in August, Hartmannella in July, and Vahlkampfia in May. Populations in profundal sediment underwent dramatic seasonal shifts, apparently in response to the seasonal chemical changes in the hypolimnion. Acanthamoeba was most prevalent in late summer, representing as much as 82% of the FLA in profundal sediment. Distribution patterns and species composition of FLA from surface water were similar to those from littoral sediment; however, a greater percentage of Naegleria was found in surface water. Numerous FLA were isolated from the neustonic community (surface film), and the number of FLA isolated in the surface film at the deep water station was found to be significantly (P less than 0.05) greater than the number from subsurface (5-10 cm) samples. In the water column, FLA populations consistently were highest in the detrital layer, which persisted at a depth of 3.0-3.4 m throughout the summer period. The large percentage of Naegleria contributing to FLA in the detrital layer suggests that Naegleria amoeboflagellates sink through the layer, flagellate, and swim back up, such migrations possibly being triggered by a reduction of nutrients below the layer or by the presence of anoxic, reducing conditions in the hypolimnion. In addition, weather events were found to play a major role in the redistribution of FLA between various habitats in the aquatic ecosystem, with such changes probably due to resuspension of FLA from littoral sediment by wind action and input from the watershed via runoff.

Amoeba↗
PubMedDate not supplied

Epidemiology of free-living ameba infections.

Small free-living amebas belonging to the genera Acanthamoeba and Naegleria occur world-wide. They have been isolated from a variety of habitats including fresh water, thermal discharges of power plants, soil, sewage and also from the nose and throats of patients with respiratory illness as well as healthy persons. Although the true incidence of human infections with these amebas is not known, it is believed that as many as 200 cases of central nervous system infections due to these amebas have occurred worldwide. A majority (144) of these cases have been due to Naegleria fowleri which causes an acute, fulminating disease, primary amebic meningoencephalitis. The remaining 56 cases have been reported as due either to Acanthamoeba or some other free-living ameba which causes a subacute and/or chronic infection called granulomatous amebic encephalitis (GAE). Acanthamoeba, in addition to causing GAE, also causes nonfatal, but nevertheless painful, vision-threatening infections of the human cornea, Acanthamoeba keratitis. Infections due to Acanthamoeba have also been reported in a variety of animals. These observations, together with the fact that Acanthamoeba spp., Naegleria fowleri, and Hartmannella sp. can harbor pathogenic microorganisms such as Legionella and or mycobacteria indicate the public health importance of these amebas.

Acanthamoeba↗