STUDIES ON PATHOGENIC FACTORS OF NON-HALOPHILIC PATHOGENIC VIBRIOS

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Some species of genus Vibrio inhabit in fresh water environments, although almost species of the genus are halophilic. Infections due to such non-halophilic vibrios including Vibrio cholerae(O1 and non-O1) or V. mimicus are caused by consumption of fresh water products or drinking water. We have studied ecology of such vibrios and obtained many isolates from river, pond, lake and estuary area. The isolates were applied to rabbit ileal loop test (RILT), and some of them showed pathogenicity in the test. It has been reported that pathogenic V. mimicus strains produce enterotoxins similar to cholera toxin or toxins produced by enterotoxigenic Escherichiacoli. However, some enterotoxin-negative V. mimicus strains showed positive reaction in RILT. A hemolysin (VMH) was purified from a V. mimicus strain and its property was studied. VMH bound to ganglioside of erythrocyte membrane and formed small pore sized ca. 3nm, and then hemolysis proceeded by colloid-osmotic manner. Existence of galact … More ose on reducing end of ganglioside molecule and a sialic acid on the galactose was important for the binding of VMH molecule. Enterotoxicity of VMH was demonstrated by RILT. V. mimicus protease (VMP) was shown to be another pathogenic factor. Namely, VMP enhanced skin vascular permeability, accelerated enterotoxic activity of the crude filtrate of the strain and agglutinated chicken erythrocytes. Furthermore, existence of another hemagglutinin (VMHA-2) was demonstrated. VMHA-2 agglutinated rabbit or mouse erythrocytes alone, but needed cooperation of VMP for agglutination of chicken erythrocyte. Role of VMHA-2 as a colonization is under investigation.Ecological study of enterotoxic V. cholerae non-O1 was carried out by direct culture method with GM1-ganglioside-enzyme linked immunosorbent assay and correlation of the vibrio with various environmental parameters were studied. Thus, various important informations to evaluate significance of non-halophilic vibrios in food sanitation were obtained. Less