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Volume 33,
Issue 3,
1990
Volume 33, Issue 3, 1990
- Review Article
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Interactions of Escherichia coli and Proteus mirabilis with mouse mononuclear phagocytes
More LessSurmmaryFive strains of enterobacteria (three of Escherichia coli and two of Proteus mirabilis) were studied to assess and compare their phagocytic uptake and intracellular killing by mouse macrophages. Each strain was injected intraperitoneally into separate groups of mice and peritoneal exudate cells were harvested after 3 min for phagocytosis to occur in vivo. Acridine orange staining showed that there were approximately 10-fold fewer intracellular P. mirabilis than E. coli cells. The average numbers of viable intracellular bacteria per leucocyte were 0.03 and 0.02 for P. mirabilis strains M13 and H1, respectively, and 0.48, 0.45, and 0.28 for E. coli strains M14, A-D M5 and H40. Thus, both P. mirabilis strains were ingested less readily than any of the three E. coli strains (p<0.01). The rates of in-vitro intracellular killing were similar for all five strains of bacteria. The intracellular killing constants (Kk) for the three mouse isolates were 0.017, 0.016 and 0.020 min for E. coli M14 and A-D M5, and P. mirabilis M13, respectively; the Kks for the two human isolates were 0.026 and 0.029/min for E. coli H40 and P. mirabilis H1, respectively. The Kks for all five strains were not significantly different. Assuming that the numbers of viable intracellular bacteria at the beginning of the assay represented 100% viability, 6-17% of the intracellular bacteria remained viable after 2 h, reflecting log10 3.9–5.6 bacteria (6–8) × 106 peritoneal exudate cells. Intravenous injection of these five strains into separate groups of mice demonstrated that the P. mirabilis strains were more virulent than the E. coli strains. Injection of each P. mirabilis strain was associated with ruffled fur and death, whereas mice given any of the three E. coli strains remained visibly healthy and none died. Consistent with these observations, quantitation of viable bacteria in the liver and spleen showed that greater numbers of P. mirabilis M13 than of E. coli M14 or A-D M5 persisted in these organs; similarly greater numbers of P. mirabilis H1 than of E. coli H40 persisted in the liver and spleen. Because the rates of intracellular killing of these five strains were similar, the relative virulence of both strains of P. mirabilis appeared to be associated with decreased phagocytic uptake rather than differences in intracellular survival.
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Functional similarity between the haemolysins of Escherichia coli and Morganella morganii
More LessSurmmaryHaemolysin produced by a clinical isolate of Morganella morganii was examined for antigenic relatedness to the haemolysin of Escherichia coli and for similarities in mode of action. The M. morganii haemolysin migrated in SDS-PAGE as a single protein band with a slightly higher molecular weight than that of E. coli haemolysin. Several murine monoclonal antibodies against E. coli haemolysin cross-reacted with the M. morganii haemolysin in Western blots. Diminished haemolysis in the presence of osmotically-stabilising solutes indicated the formation of a pore by M. morganii haemolysin with an effective diameter of 1.5–3 nm. Results from dose-response experiments indicated that a single hit was sufficient for lysis of an erythrocyte. Detergent solubilisation of toxin-treated membranes led to recovery of bound toxin exclusively in monomeric form. M. morganii haemolysin was a potent leucocidin, that caused rapid leakage of ATP and death of human polymorphonuclear leucocytes. Under in-vitro conditions M. morganii haemolysin displayed similar leucocidal and haemolytic efficiency. The data demonstrate that M. morganii haemolysin shows functional properties virtually identical with those of E. coli haemolysin.
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Hepatotoxic activity of Campylobacter jejuni
More LessSurmmaryHepatotoxic factor(s) were isolated from whole-cell lysates of Campylobacter jejuni GIFU 8734 and purified by chromatography. A single intravenous injection of 10 μ10 of this factor reproducibly produced hepatitis in mice, as determined by histology and liver function tests. The hepatic lesions were very similar to those evoked by C. jejuni infection. Tissue-culture studies with mouse hepatocytes demonstrated that low concentrations of the factor caused release of hepatic enzymes into the medium without appreciable cytolysis. High concentrations of the factor induced cytolysis. These effects were neutralised by antiserum to the factor, but not by antisera to the lipopolysaccharide of C. jejuni or to the heat-labile enterotoxin of Escherichia coli. Among 20 clinical isolates of C. jejuni, only four evoked hepatitis in mice and produced the hepatotoxic factor.
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Identification of Fusobacterium species by the electrophoretic migration of glutamate dehydrogenase and 2-oxoglutarate reductase in relation to their DNA base composition and peptidoglycan dibasic amino acids
More LessSurmmaryRapid identification of Fusobacterium spp. is hampered by their inability to ferment carbohydrates and the availability of relatively few useful phenotypic characters. In an attempt to identify new diagnostic markers for species, we reported recently the potential utility of glutamate dehydrogenase (GDH) electrophoretic mobilities for distinguishing eight species of Fusobacterium. We have extended these observations to include all recognised members of the genus except F. prausnitzii and F. perfoetens, and our results show that they cluster into three broad electrophoretic groups. Some species, such as F. periodontium, F. simiae and F. necrophorum, possessed GDH with similar electrophoretic mobilities. However, within such clusters, the electrophoretic migration of 2-oxoglutarate reductase (OGR) distinguished between species. Neither GDH or OGR mobility alone clearly differentiated all species, but their combined use provided unambiguous discrimination of all species except F. varium and F. mortiferum. The DNA base compositions of all species except F. naviforme (ATCC 25832) and F. sulci, were within the range 26–34 mol% G + C, suggesting the genus may be homogeneous. However, the peptidoglycan composition divided the genus into two major groups that contained either lanthionine or diaminopimelic acid; F. mortiferum peptidoglycan contained both dibasic amino acids.
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A rat model of Staphylococcus aureus chronic osteomyelitis that provides a suitable system for studying the human infection
More LessSurmmaryChronic osteomyelitis was produced by inoculating Staphylococcus aureus into rat tibia. The infection was characterised grossly by bone deformation and histopathologically by inflammation and the presence of coccal organisms sequestered within the bone tissue. Further observations by scanning electronmicroscopy demonstrated bacteria in microcolonies surrounded by dehydrated amorphous material that was considered to be glycocalyx. Transmission electronmicroscopy, when aided by antibody stabilisation, revealed extensive glycocalyx production within the tibia. These findings indicate that the rat model of chronic S. aureus osteomyelitis mimics the human infection with respect to the sessile mode of growth of bacteria within the bone. Serum antibody levels were assayed by ELISA and immunoblotting procedures. After an initial increase, ELISA titres remained relatively stable, apparently indicating the establishment of chronic osteomyelitis, whereas in immunoblotting an increase in titre over the course of infection was observed. Whole-cell ELISA revealed less subtle differences in antibody titre than did immunoblotting with cell-wall antigen. We found that mid-range antigens, including an antigen implicated as protein A, featured prominently in the immune response in this model of infection.
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Vaccination of mice with lipopolysaccharide (LPS) and LPS-derived immuno-conjugates from Leptospira interrogans
A. Midwinter, S. Faine and B. AdlerSurmmaryMice were vaccinated with lipopolysaccharide (LPS) from Leptospira interrogans serovar pomona or hardjo, or with the polysaccharide (PS) fraction of the LPS, or with an immunoconjugate of PS and diphtheria toxoid (DT). Maximum agglutinin titres were found 6-10 weeks after vaccination with LPS or PS-DT conjugate; the latter elicited antibody titres at least 10 times higher than those produced in response to LPS. Animals failed to react significantly to PS. Titres elicited by antigens of serovar pomona were higher than those elicited by serovar hardjo.
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