Live attenuated
A live attenuated Edwardsiella ictaluri bacterium lacking a viable gene encoding a functional evpB protein and a method of using the same to protect fish against infection from virulent Edwardsiella ictaluri . The methods and compositions for protecting fish against infection from virulent Edwardsiella ictaluri comprising administering to a fish a therapeutically effective amount of an attenuated Edwardsiella ictaluri bacterium lacking a viable gene encoding a functional protein selected from the group consisting of evpB, fur and hfq. The bacterium may include an insertion and/or deletion mutation in the gene. The fish include catfish, preferably catfish fingerling or a catfish fry. The composition may be delivered via immersion delivery, an injection delivery, an oral delivery, or combinations thereof.
1. A modified Edwardsiella ictaluri bacterium, the modified Edwardsiella ictaluri bacterium lacking a viable gene encoding a functional EvpB protein by having a deletion of the coding sequence of the evpB gene.
2. The modified Edwardsiella ictaluri bacterium of claim 1 , wherein the mutation in the evpB gene is a mutation selected from the group consisting of an insertion mutation and a deletion mutation.
3. The modified Edwardsiella ictaluri bacterium of claim 2 , wherein the mutation in the evpB gene is an in-frame deletion.
4. A vaccine for protecting fish against Edwardsiella ictaluri infection comprising an immunogenically effective amount of an attenuated Edwardsiella ictaluri bacterium, the bacterium lacking a viable gene encoding a functional protein by having deletions of the coding sequence of ferric uptake regulator (fur) and hfq genes.
5. A composition comprising an amount of live attenuated Edwardsiella ictaluri bacterium sufficient for protecting fish against infection from virulent Edwardsiella ictaluri , the bacterium lacking a viable gene encoding a functional EvpB protein by having a deletion of the coding sequence of evpB and at least one other gene selected from the group consisting of ferric uptake regulator (fur) and hfq genes, and one or more of the group consisting of a pharmaceutically-acceptable vehicle, a carrier, and an excipient.
6. The composition of claim 5 , wherein the composition is formulated for delivery to fish by the method selected from the group consisting of an immersion delivery, an injection delivery, an oral delivery, or combinations thereof.
7. A method for protecting fish against infection from virulent Edwardsiella ictaluri comprising: administering to a fish a therapeutically effective amount of an attenuated Edwardsiella ictaluri bacterium lacking a viable gene encoding a functional EvpB protein by having at least one deletion of the coding sequence of the evpB gene.
8. The method of claim 7 , wherein the administering step is selected from a group consisting of immersion delivery, injection delivery, oral delivery, and combinations thereof.
9. The method of claim 7 , wherein the fish is a catfish.
10. The method of claim 7 , wherein the attenuated Edwardsiella ictaluri bacterium is mixed with a fish feed to form a fish feed mixture, and wherein the fish feed mixture is delivered to the fish for oral consumption.