[Use of the DNA-DNA hybridization method on filters for determining the toxic potency of atypical strains of Vibrio cholerae isolated from natural sources].

The methods of the radioimmunoassay and the blot hybridization of restricted fragments of chromosomal DNA have been used for the characterization of V. cholerae atypical strains isolated from the natural environment. For all strains under study, the radioimmunoassay has been found to yield the most sharply defined data characterizing their atoxigenicity.

[Comparative study of the action of Vibrio cholerae enterotoxin, thermolabile Escherichia coli toxin and a Salmonella typhimurium filtrate on the small intestine of laboratory animals].

The results of the comparative study of the effects produced by V. cholerae enterotoxin E. coli thermolabile toxin (TL-toxin) and S.

[Determination of cholera enterotoxin in supernatants of homogenates from the wall of the small intestine in rabbits in the passive immune hemolysis reaction].

The article presents the data indicating that suckling rabbits can be used as a model, specific only for enterotoxin-producing Vibrio eltor strains. The signs characteristic of low virulence may appear as the consequence of the action of other products resulting from the vital activity of vibrios. No strains capable of producing toxin only in vivo or in vitro have been detected.

[Role of enterotoxin and neuraminidase in the biological activity of E1 Tor vibrios].

The biological activity of the toxigenic strains of cholera vibrios in suckling rabbits used as a model is manifested irrespective of the amount of neuraminidase produced by these strains. Neuraminidase is important only in low-cholerogenic strains, which is confirmed by a significantly greater death rate among suckling rabbits infected with cultures producing 40-2560 ng/ml of the exoenzyme in comparison with that among suckling rabbits infected with strains producing less than 10 ng/ml of the exoenzyme, or not producing it at all. The relation between the amounts of enterotoxin and neuraminidase, produced in vitro, and the biological activity of strains in suckling rabbits has been established, which allows one to study the virulence of strains in the passive immune hemolysis and aggregate hemagglutination tests.