Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China; Livestock and Poultry Epidemic Diseases Research Center of Anhui Province, Institute of Animal Husbandry and Veterinary Science, Anhui Academy of Agricultural Sciences, Hefei, Anhui 230031, China.
Anhui Province Key Laboratory of Veterinary Pathobiology and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China.
Comp Immunol Microbiol Infect Dis. 2021 Dec;79:101722. doi: 10.1016/j.cimid.2021.101722. Epub 2021 Nov 18.
The Escherichia coli type III secretion system 2 (ETT2) is found in most pathogenic E. coli strains. Although many ETT2 gene clusters carry multiple genetic mutations or deletions, ETT2 is known to be involved in bacterial virulence. To date, no studies have been conducted on the role of ETT2 in the virulence of avian pathogenic Escherichia coli (APEC), which harbours ETT2. Thus, we deleted the ETT2 of APEC strain and evaluated the phenotypes and pathogenicities of the mutant. The results showed that deletion of ETT2 had no effect on APEC growth, but significantly promoted biofilm formation. In addition, as compared to the wild-type （WT） strain, the ETT2 deletion significantly promoted adherence to and invasion of DF-1 chicken fibroblasts and facilitated survival in the sera of specific-pathogen-free chickens. Analysis of the role of ETT2 in animal infection models demonstrated that the distribution of viable bacteria in the blood and organs of chicks infected with the ΔETT2 was significantly higher than those infected with WT. The results of RNA sequencing indicated that multiple genes involved in biofilm formation, lipopolysaccharide components, fimbrial genes and virulence effector proteins are regulated by ETT2. Collectively, these results implicated ETT2 is involved in the biofilm formation and pathogenicity of APEC.
大肠杆菌 III 型分泌系统 2（ETT2）存在于大多数致病性大肠杆菌菌株中。尽管许多 ETT2 基因簇携带多种基因突变或缺失，但已知 ETT2 与细菌毒力有关。迄今为止，尚未有研究探讨 ETT2 在携带 ETT2 的禽致病性大肠杆菌（APEC）中的毒力作用。因此，我们删除了 APEC 菌株的 ETT2，并评估了突变体的表型和致病性。结果表明，ETT2 的缺失对 APEC 的生长没有影响，但显著促进了生物膜的形成。此外，与野生型（WT）菌株相比，ETT2 的缺失显著促进了对 DF-1 鸡成纤维细胞的黏附和侵袭，并促进了在无特定病原体鸡血清中的存活。在动物感染模型中分析 ETT2 的作用表明，与 WT 相比，感染ΔETT2 的雏鸡血液和器官中活菌的分布明显更高。RNA 测序的结果表明，生物膜形成、脂多糖成分、菌毛基因和毒力效应蛋白相关的多个基因受到 ETT2 的调控。综上所述，这些结果表明 ETT2 参与了 APEC 的生物膜形成和致病性。
