The fhuCD system and its importance in Edwardsiella ictaluri virulence have not been
studied yet. Previously, we constructed E. ictaluri ΔfhuCD mutants by in-frame deletion and
allelic exchange. In the present study, the virulence of the EiΔfhuCD mutant was evaluated
by immersion challenge using Specific Pathogen-Free channel catfish fingerlings and the
ability of this mutant to protect the channel catfish against E. ictaluri was evaluated. Also,
the ability of EiΔfhuCD mutant to grow in the presence of iron chelator 2,2’ Dipyridyl was
assayed. The results indicated that little or no attenuation in EiΔfhuCD (40.00% mortality)
was observed as compared to the parent E. ictaluri (%46.42). The channel catfish treated
with EiΔfhuCD mutant showed high relative percent survival rates (average 94.72%) after
re-challenge with E. ictaluri wild type. It was also found that the deletion of the E. ictaluri
fhuCD operon did not affect E. ictaluri growth under iron-replete and iron-restricted
conditions. Taken together, such data suggest that fhuCD operon is partial essential in E.
ictaluri full virulence in channel catfish. |
