Deletion of luxS further attenuates the virulence of the avian pathogenic Escherichia coli aroA mutant.
In this study, an aroA-deletion avian pathogenic Escherichia coli (APEC) mutant (strain DE17ΔaroA) and aroA and luxS double deletion APEC mutant (strain DE17ΔluxSΔaroA) were constructed from the APEC DE17 strain. The results showed that as compared to DE17ΔaroA, the virulence of DE17ΔluxSΔaroA was further attenuated by 200- and 31.7-fold, respectively, in ducklings based on the 50% lethal dose. The adherence and invasion abilities of DE17ΔluxSΔaroA and DE17ΔaroA were reduced by 36.5%/42.5% and 25.8%/29.3%, respectively, as compared to the wild-type strain DE17 (p < 0.05 and 0.01, respectively). Furthermore, in vivo studies showed that the bacterial loads of DE17ΔluxSΔaroA were reduced by 8400- and 11,333-fold in the spleen and blood of infected birds, respectively, while those of DE17ΔaroA were reduced by 743- and 1000-fold, respectively, as compared to the wild-type strain DE17. Histopathological analysis showed both that the mutants were associated with reduced pathological changes in the liver, spleen, and kidney of ducklings, and changes in DE17ΔluxSΔaroA-infected ducklings were reduced to a greater degree than those infected with DE17ΔaroA. Real-time polymerase chain reaction analysis further demonstrated that the mRNA levels of virulence-related genes (i.e., tsh, ompA, vat, iucD, pfs, fyuA, and fimC) were significantly decreased in DE17ΔaroA, especially in DE17ΔluxSΔaroA, as compared to DE17 (p < 0.05). In addition, the deletion of aroA or the double deletion of aroA and luxS reduced bacterial motility. To evaluate the potential use of DE17ΔluxSΔaroA as a vaccine candidate, 50 7-day-old ducklings were divided randomly into five groups of ten each for the experiment. The results showed that the ducklings immunized with inactivated DE17, DE17ΔluxS, DE17ΔaroA, and DE17ΔluxSΔaroA were 70.0%, 70.0%, 70.0, and 80.0% protected, respectively, after challenge with strain APEC DE17. The results of this study suggest that the double deletion of luxS and aroA attenuated APEC pathogenicity and DE17ΔluxSΔaroA was more appropriate for development of a future vaccine against avian colibacillosis than DE17ΔaroA.
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China.
Xiangan
X
Han
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China; College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China.
Hao
H
Bai
College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China.
Jian
J
Tu
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China.
Lijun
L
Yang
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China.
Da
D
Xu
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China.
Shaohui
S
Wang
College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China.
Kezong
K
Qi
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China.
Guobo
G
Fan
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China; College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China.
Yuxi
Y
Zhang
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China.
Jiakun
J
Zuo
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China.
Mingxing
M
Tian
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China.
Chan
C
Ding
Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences (CAAS), 518 Ziyue Road, Shanghai 200241, PR China. Electronic address: yus@shvri.ac.cn.
Shengqing
S
Yu
D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase / Q000172:deficiency / Q000235:genetics*; D000825:Animal Structures / Q000382:microbiology / Q000473:pathology; D000818:Animals; D000831:Animals, Newborn; D001422:Bacterial Adhesion; D058491:Bacterial Load; D001426:Bacterial Proteins / Q000235:genetics*; D013437:Carbon-Sulfur Lyases / Q000172:deficiency / Q000235:genetics*; D004372:Ducks; D004926:Escherichia coli / Q000235:genetics / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000473:pathology / Q000662:veterinary; D022361:Escherichia coli Vaccines / Q000008:administration & dosage / Q000276:immunology; D017353:Gene Deletion; D006651:Histocytochemistry; D011201:Poultry Diseases / Q000382:microbiology / Q000473:pathology; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000276:immunology; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics*
D001426:Bacterial Proteins; D022361:Escherichia coli Vaccines; D014613:Vaccines, Attenuated; D037521:Virulence Factors; D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria
Avian pathogenic Escherichia coli; Pathogenicity; aroA mutant; luxS