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ABSTRACT: Entero-invasive Escherichia coli (EIEC) and shigellae were tested for contact-haemolysin (CH) with red blood cells (RBCs) of guinea-pig, rabbit, rat, mouse, monkey, man, sheep and chicken; all bacteria showed the best lysis with guinea-pig RBCs. The best culture medium for CH activity of shigellae was tryptic soy broth, and for EIEC it was casamino acid-yeast extract broth with 1 mM CaCl2. CH production by all species was best at the slightly alkaline pH which is optimal for growth; it was also dependent on the presence of a large (140-Mda) plasmid. Pre-treatment of bacteria with homologous antisera inhibited CH activity. Various treatments of bacterial cells and RBCs suggested that CH may be a protein molecule, and that a chitotriose-like moiety may serve as CH receptor. RBCs that were incubated with bacteria at 4 degrees C, or with heat-killed bacteria at 37 degrees C, were not lysed; also, isolated cell-surface components (lipopolysaccharide and outer-membrane protein) did not lyse RBCs. This suggests that metabolically active cells are required for CH activity. Production of CH by both EIEC and shigellae is consistent with a common mechanism for the virulence of these organisms.
Journal of Medical Microbiology 01/1992; 35(6):330-7. · 2.50 Impact Factor
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Journal of Antimicrobial Chemotherapy 11/1991; 28(4):599-601. · 5.07 Impact Factor
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Journal of Antimicrobial Chemotherapy 05/1991; 27(4):554-5. · 5.07 Impact Factor
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ABSTRACT: The association of plasmids with virulence characters and O-antigen expression was studied in two virulent and seven avirulent mutant strains of Shigella dysenteriae type 1. Deletion of a 12-Mda segment from a 140-Mda plasmid in two smooth avirulent mutants made the derivatives avirulent in the Sereny test and non-invasive in HeLa cells. The mutants were unable to bind Congo red, and did not express the virulence marker antigen. Mutants completely lacking the 140-Mda plasmid also showed similar avirulent characters. However, rough mutants retained the ability to bind Congo red. Our results indicate that the essential gene(s) for virulence may be located on the 140-Mda plasmid, a small deletion from which may lead to avirulence. This deletion did not affect the protein antigen expression nor change their antigenicity. Analysis of lipopolysaccharide (LPS) patterns showed that strains containing the 6-Mda plasmid produced the complete LPS and were smooth, whereas strains containing either the 140- or a 4- or 2-Mda plasmid, in the absence of the 6-Mda plasmid, produced smaller amounts of O antigen and were rough. Western-blot analysis and crossed immuno-electrophoresis gave similar results. The 140-, 4-, or 2-Mda plasmid, in the absence of the 6-Mda plasmid, may code for non-specific galactosyl transferase-like activity which can add, non-specifically and at a reduced level, the galactose residue (the first sugar in the O antigen repeat unit) to the LPS core.(ABSTRACT TRUNCATED AT 250 WORDS)
Journal of Medical Microbiology 10/1990; 33(1):1-9. · 2.50 Impact Factor
