title: Effect of multiple mutations in tricarboxylic acid cycle and one-carbon metabolism pathways on Edwardsiella ictaluri pathogenesis.
abstract: Edwardsiella ictaluri is a Gram-negative facultative intracellular pathogen causing enteric septicemia of catfish (ESC). We have shown recently that tricarboxylic acid cycle (TCA) and one-carbon (C1) metabolism are involved in E. ictaluri pathogenesis. However, the effect of multiple mutations in these pathways is unknown. Here, we report four novel E. ictaluri mutants carrying double gene mutations in TCA cycle (EiΔmdhΔsdhC, EiΔfrdAΔsdhC), C1 metabolism (EiΔglyAΔgcvP), and both TCA and C1 metabolism pathways (EiΔgcvPΔsdhC). In-frame gene deletions were constructed by allelic exchange and mutants' virulence and vaccine efficacy were evaluated using in vivo bioluminescence imaging (BLI) as well as end point mortality counts in catfish fingerlings. Results indicated that all the double gene mutants were attenuated compared to wild-type (wt) E. ictaluri. There was a 1.39-fold average reduction in bioluminescence, and hence bacterial numbers, from all the mutants except for EiΔfrdAΔsdhC at 144 h post-infection. Vaccination with mutants was very effective in protecting channel catfish against subsequent infection with virulent E. ictaluri 93-146 strain. In particular, immersion vaccination resulted in complete protection. Our results provide further evidence on the importance of TCA and C1 metabolism pathways in bacterial pathogenesis.
authors.affiliation: College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA.
authors.forename: N
authors.initials: N
authors.lastname: Dahal
authors.affiliation: Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Benha University, Moshtohor-Toukh, Egypt.
authors.forename: H
authors.initials: H
authors.lastname: Abdelhamed
authors.affiliation: College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA.
authors.forename: J
authors.initials: J
authors.lastname: Lu
authors.affiliation: College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA. Electronic address: karsi@cvm.msstate.edu.
authors.forename: A
authors.initials: A
authors.lastname: Karsi
authors.affiliation: College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA. Electronic address: lawrence@cvm.msstate.edu.
authors.forename: M L
authors.initials: ML
authors.lastname: Lawrence
mesh_terms: D000818:Animals; D001428:Bacterial Vaccines / Q000008:administration & dosage*; D002244:Carbon / Q000378:metabolism; D002952:Citric Acid Cycle / Q000235:genetics; D020610:Edwardsiella ictaluri / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism / Q000472:pathogenicity; D004756:Enterobacteriaceae Infections / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary*; D005393:Fish Diseases / Q000276:immunology / Q000382:microbiology* / Q000517:prevention & control; D017353:Gene Deletion; D005838:Genotype; D007059:Ictaluridae / Q000276:immunology / Q000382:microbiology; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D009154:Mutation; D014611:Vaccination / Q000662:veterinary; D014774:Virulence / Q000235:genetics
chemical_list: D001428:Bacterial Vaccines; D002244:Carbon
keywords: Channel catfish; Edwardsiella ictaluri; Glycine cleavage protein; Ictalurus punctatus; Tricarboxylic acid cycle; Vaccine