title: Role of the lpxM lipid A biosynthesis pathway gene in pathogenicity of avian pathogenic Escherichia coli strain E058 in a chicken infection model.
abstract: Lipopolysaccharide (LPS) is a major surface component of avian pathogenic Escherichia coli (APEC), and is a possible virulence factor in avian infections caused by this organism. The contribution of the lpxM gene, which encodes a myristoyl transferase that catalyzes the final step in lipid A biosynthesis, to the pathogenicity of APEC has not previously been assessed. In this study, an isogenic lpxM mutant, E058ΔlpxM, was constructed in APEC O2 strain E058 and then characterized. Structural analysis of lipid A from the parental strain and derived mutant showed that E058ΔlpxM lacked one myristoyl (C14:0) on its lipid A molecules. No differences were observed between the mutant and wild-type in a series of tests including growth rate in different broths and ability to survive in specific-pathogen-free chicken serum. However, the mutant showed significantly reduced invasion and intracellular survival in the avian macrophage HD11 cell line (P<0.05). Nitric oxide production reduction (P<0.05) and cytokine gene expression downregulation (P<0.05 or P<0.01) also showed in HD11 treated with E058ΔlpxM-derived LPS compared with that in cells treated with E058-derived LPS at different times. Compared to the parental strain E058, E058ΔlpxM had a significant reduction in bacterial load in heart (P<0.01), liver (P<0.01), spleen (P<0.01), lung (P<0.05), and kidney (P<0.05) tissues. The histopathological lesions in visceral organs of birds challenged with the wild-type strain were more severe than in birds infected with the mutant. However, the E058ΔlpxM mutant showed a similar sensitivity pattern to the parental strain following exposure to several hydrophobic reagents. These results indicate that the lpxM gene is important for the pathogenicity and biological activity of APEC strain 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: Huiqing
authors.initials: H
authors.lastname: Xu
authors.forename: Jielu
authors.initials: J
authors.lastname: Ling
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Gao
authors.forename: Hongbo
authors.initials: H
authors.lastname: He
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Mu
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yan
authors.forename: Song
authors.initials: S
authors.lastname: Gao
authors.forename: Xiufan
authors.initials: X
authors.lastname: Liu
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D053898:Biosynthetic Pathways / Q000235:genetics; D002645:Chickens / Q000378:metabolism / Q000382:microbiology; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D008050:Lipid A / Q000096:biosynthesis*; D011201:Poultry Diseases / Q000382:microbiology*; D013047:Specific Pathogen-Free Organisms; D014774:Virulence
chemical_list: D029968:Escherichia coli Proteins; D008050:Lipid A; D000217:Acyltransferases; C097895:MsbB protein, E coli
keywords: Avian pathogenic Escherichia coli; Mutation; Myristoyl transferase; Pathogenicity; lpxM