Live attenuated bacteria vaccines against enteric septicemia of fish, especially catfish, and methods related to the same. Mutant strains of the bacteria Edwardsiella ictaluri (a pathogenic bacterial strain of Enterobacteriaceae) are provided. The mutant Edwardsiella ictaluri bacteria (or other pathogenic bacterial strain of Enterobacteriaceae) contain one or more gene deletions or disruptions that result in less virulent bacterial strains as live attenuated vaccine compositions against virulent wild-type Edwardsiella ictaluri bacteria (or other pathogenic bacterial strain of Enterobacteriaceae). The mutant strains showing the best immunological protection and safety as a vaccine are the triple mutants ESC-NDKL1 (ΔgcvPΔsdhCΔfrdA) strain and ESC-NDKL2 (ΔgcvPΔsdhCΔmdh) strain, with the ESC-NDKL1 strain providing the greatest safety and efficacy of these two triple mutants.
