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At least 217 records · Page 12Linked to original sources
PubMedDate not supplied

The intracellular multiplication of Legionella pneumophila in protozoa from hospital plumbing systems.

Between October 1987 and March 1989, we tested 144 water samples obtained from the plumbing and cooling tower systems of 5 Paris hospitals for the presence of legionellae and amoebae. Of the samples tested for Legionella, 67 out of 144 (46.5%) were positive, and 82 out of 116 tested for amoebae (70.7%) were positive. The ability of protozoa to support the multiplication of legionella was shown by incubating samples at 35.5 degrees C for 7-15 days. Prior to determining the presence of legionellae and amoebae, 51 of the 144 samples were incubated. After incubation, 22 out of 25 (88%) samples which were positive for the presence of both Legionella and amoebae showed multiplication of Legionella. In 3 out of the 25 (12%) samples containing Legionella and amoebae, Legionella failed to multiply. Six out of the 51 (11.8%) samples which were negative in direct culture for Legionella but positive for amoebae, became positive after incubation. Legionella did not multiply in samples negative for amoebae, nor was there proliferation in samples after filtration through a 1.2-microns membrane followed by incubation for the same period and temperature. Strains of Legionella pneumophila serogroup 1 and serogroup 6 (SG1 and SG6), including 3 patient isolates and 2 environmental isolates, were cocultured with 2 strains of amoebae and Tetrahymena pyriformis. Plate counts, Gimenez staining and electron microscopy demonstrated that intracellular legionellae proliferation occurred.

Air Conditioning↗
PubMed2006

[Intra-amoebal development of Legionella pneumophila and the potential role of amoebae in the transmission of Legionnaires' disease].

Legionnaires' disease is one of the major infectious risks related to hospital water systems. It is commonly accepted, that the disease is transmitted to man mostly by inhalation of water aerosols contaminated by Legionella pneumophila. The ability of L. pneumophila to multiply intracellularly within some amoebae better explains the ecology, the pathogenicity, and the virulence of this bacterium against human alveolar macrophages. The presence of these amoebae in water systems located where cases of Legionnaire's disease broke out, partly explains the difficulty in eradicating Legionella. Some studies also show that amoebae can play a major role in the transmission of the disease to man. Some other studies point out that inhaled amoebae could be involved in the pathogenesis of Legionnaire's disease. Future strategies to prevent the transmission of Legionella will probably have to include efficient treatments against amoebae.

Acanthamoeba↗
PubMedDate not supplied

Phagocytes from both vertebrate and invertebrate species use "coiling" phagocytosis.

Coiling phagocytosis has been observed previously only by chance, and there has been no systematic investigation of this uptake mechanism. Therefore, a comparative electron microscopical study was performed. Different human and murine cell populations, phagocytes from various vertebrate and invertebrate species, and predatory amoebae were incubated with Borrelia burgdorferi, one of the microbes known to induce coiling phagocytosis, to study the uptake mechanisms used. In this model, coiling phagocytosis was observed with both vertebrate and invertebrate species but not with amoebae. With cells from humans and mice, this uptake mechanism was restricted to phagocytic cells of myeloid origin. The coiled membrane gaps did not give rise to phagosomes; instead, membrane fusion was followed by membrane dissipation. Thus, coiling of B. burgdorferi apparently is an alternative uptake mechanism used by metazoan phagocytes, involving special membrane processing. However, coiling phagocytosis may show different features with different microbes.

Animals↗
PubMed1975

Soil ameba infection. Specific indirect immunoenzymatic (peroxidase) staining of formalin-fixed paraffin sections.

This report describes the use of the immunoenzymatic (peroxidase) method to identify the species and to stain distinctively the amebas in formalin-fixed paraffin-mounted sections. This permits the use of hematoxylin and eosin counterstaining. The method, now well developed by others for many purposes, is an alternative to immunofluorescence and seems to offer a number of advantages and a lesser number of disadvantages.

Amebiasis↗
PubMed1975

A case of hartmannellid amebic meningoencephalitis in Zambia.

A case of amebic meningoencephalitis recognized in an adult Zambian is described. This is the first authenticated case from Africa. The morphologic features of the organism, its ability to form cysts in tissue, and the granulomatous tissue response denote that the ameba is an hartmannellid rather than a Naegleria. Free-living amebas of the family Hartmannellidae have not been incriminated before as a cause of primary amebic meningoencephalitis in man. To our knowledge this is the only case where such an ameba was responsible for fulminating meningoencephalitis. The presence of the amebas in a cellulocutaneous abdominal lesion suggests hematogenous dissemination.

Amebiasis↗
PubMed1977

Scanning electron microscopy of Acanthamoeba culbertsoni as observed in the subarachnoid space.

Scanning electron microscopy was used to study the pathogenic protozoan, Acanthamoeba culbertsoni, in the leptomeningeal subarachnoid space surrounding the spinal cord of the experimentally inoculated dog. Know to inhabit such areas as moist soils, stagnant waters, and sewage around the world, these protozoans have been identified as etiologic agents in numerous cases of meningoencephalitis. Infection occurs via a nasopharyngeal inoculation, through penetration of the olfactory mucosal epithelium and cribriform plate, into the subarachnoid space, whence it gains access to the central nervous system. Stock preparations of these amebae extracted directly from their culture medium for scanning microscopic study provided an index for their identification within the subarachnoid space and also permitted a heretofore unobserved survey of their pleomorphic surface features. From the observations of others, it had appeared that the ultimate portal of entry into the central nervous system involved some type of cytolytic process; however, this study illustrates an action of simple diapedesis in which the organisms seek a pathway of least resistance; namely the naturally-occurring pial fenestrations.

Animals↗
PubMed2006

Homologs of mitochondrial transcription factor B, sparsely distributed within the eukaryotic radiation, are likely derived from the dimethyladenosine methyltransferase of the mitochondrial endosymbiont.

Mitochondrial transcription factor B (mtTFB), an essential component in regulating the expression of mitochondrial DNA-encoded genes in both yeast and humans, is a dimethyladenosine methyltransferase (DMT) that has acquired a secondary role in mitochondrial transcription. So far, mtTFB has only been well studied in Opisthokonta (metazoan animals and fungi). Here we investigate the phylogenetic distribution of mtTFB homologs throughout the domain Eucarya, documenting the first examples of this protein outside of the opisthokonts. Surprisingly, we identified putative mtTFB homologs only in amoebozoan protists and trypanosomatids. Phylogenetic analysis together with conservation of intron positions in amoebozoan and human genes supports the grouping of the putative mtTFB homologs as a distinct clade. Phylogenetic analysis further demonstrates that the mtTFB is most likely derived from the DMT of the mitochondrial endosymbiont.

Acanthamoeba castellanii↗
PubMed1996

The use of differential display-PCR to isolate and characterize a Legionella pneumophila locus induced during the intracellular infection of macrophages.

The differential display (DD)-PCR technique has been modified to identify prokaryotic cDNA fragments that are differentially induced by facultative intracellular bacteria in response to the intracellular environment of eukaryotic cells. Several DD-PCR fragments identified from the intracellular bacterium Legionella pneumophila were induced at 4 h post-infection of the U937 macrophage-like cells. From these, a 700 bp fragment was cloned and sequenced. Neither the DNA sequence nor the predicted protein sequence from the open reading frame has similarity to other sequences in genetic databases. Transcription of the chromosomal locus containing the 700 bp fragment (eml, for early stage macrophage-induced locus) was induced by intracellular bacteria during the first few hours post-infection of macrophages but the expression was downregulated by 12 h post-infection. Transcription of eml was not growth phase-related in vitro, and was not affected by in vitro stress stimuli. A 3.7 kb EcoRI genomic fragment containing the 700 bp DD-PCR product was cloned. Six mini-Tn 10 insertions in the 3.7 kb EcoRI fragment were recombined into the L. pneumophila chromosome. Compared to the wild-type strain, five of the eml isogenic mutants had a similar phenotype of reduced cytopathicity to the U937 cells, showed a 100-fold increase in killing by macrophages during the first 5 h of the intracellular infection, and showed a 100-fold increase in killing during the first 24h of infection of the amoeba Hartmanella vermiformis. The 6th mutant had a phenotype indistinguishable from the wild-type strain. The cytopathicity defect of the mutants to the U937 cells was restored to wild-type levels by complementation of the mutants with a plasmid containing the 3.7 kb EcoRI fragment. These data showed that the 3.7 kb fragment containing eml is a novel L. pneumophila locus whose expression is uniquely induced by non-stress stimuli during early stages of the intracellular infection of phagocytic cells. Expression of this locus is required for survival of L. pneumophila within macrophages and within amoebae during early stages of the infection.

Animals↗