abstract |
Salmonella typhi strain Ty 2 is subjected to ultraviolet light, and the mutants so produced are screened for selection of strains defective in the enzyme uridine diphosphogalactose-4-epimerase, and a live vaccine is prepared from the selected and carefully isolated strains in the usual manner. The strains are also identified by their sharply reduced galactokinase and galactose-1-phosphate uridylyltransferase activity, as compared to the parent strain. |