title: Construction of iucB and iucBiutA mutants of avian pathogenic Escherichia coli and evaluation of their pathogenicity.
abstract: Aerobactin counts for much to the pathogenesis of avian pathogenic Escherichia coli (APEC), iutA is responsible for the expression of a specific outer membrane receptor protein for ferric aerobactin, and iucB is involved in the aerobactin synthesis. To our knowledge, the contribution of iucB to the pathogenicity of APEC has not been assessed till now. In this study, the mutants E058ΔiucB and E058ΔiucBΔiutA were constructed and characterized. There were no differences observed in a series of tests including the embryo lethality, invasion assay in HD11 cells and the ability to survive in SPF chicken serum. Meanwhile, the mutants showed decreased pathogenicity as compared with the wild-type strain through a series of experiments in vivo. The mutants E058ΔiucB and E058ΔiucBΔiutA greatly reduced in all of the tested tissues in vivo persistence (p<0.001). In the meantime, the mutants had no ability to produce aerobactin. Reintroduction of the iucB gene on a multicopy expression plasmid pGEX-6p-1 restored the capacity to produce aerobactin as similar to that of wild-type strain E058. The results indicated that the iucB gene related virulence factors including the iron assimilation system were important for the pathogenesis of APEC E058. As showed in the in vivo competition assay, compared to the parental strain E058, E058ΔiucB had a significant reduction of bacterial loads in heart (p<0.01), liver (p<0.01), kidney (p<0.01), spleen (p<0.05) and lung (p<0.05), respectively, while E058ΔiucBΔiutA had a sharp reduction in all of the five tissues to be tested (p<0.001). These results suggested that the single gene either iucB or iutA was likely to be involved directly or indirectly in iron uptake for the pathogenicity of APEC E058, and there was an obviously synergistic effect between iucB and iutA genes on the pathogenicity of APEC E058.
authors.affiliation: Animal Infectious Disease Laboratory, Ministry of Education Key Lab for Avian Preventive Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu 225009, PR China.
authors.forename: Liping
authors.initials: L
authors.lastname: Xiong
authors.forename: Jielu
authors.initials: J
authors.lastname: Ling
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Gao
authors.forename: Yefei
authors.initials: Y
authors.lastname: Zhou
authors.forename: Tiantian
authors.initials: T
authors.lastname: Li
authors.forename: Song
authors.initials: S
authors.lastname: Gao
authors.forename: Xiufan
authors.initials: X
authors.lastname: Liu
mesh_terms: D000818:Animals; D002460:Cell Line; D002642:Chick Embryo; D002645:Chickens; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity* / Q000502:physiology; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D055786:Gene Knockout Techniques; D005798:Genes, Bacterial / Q000235:genetics*; D006877:Hydroxamic Acids / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D008264:Macrophages / Q000382:microbiology; D010957:Plasmids; D011201:Poultry Diseases / Q000382:microbiology*; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D006877:Hydroxamic Acids; D037521:Virulence Factors; C031819:aerobactin; D007501:Iron