Abstract
To further investigate the role of capsule involved in virulence of Pasteurella multocida P-1059 (A:3), a hexB deleted mutant was constructed by homologous recombination. The DNA replacement was confirmed by PCR, Reverse transcription (RT)-PCR and DNA sequencing. Experiments were conducted to compare the differences of biological characteristics such as capsular structure, capsular polysaccharide content, virulence and serum resistance between the hexB deleted mutant of ΔhexB and wild-type strain P-1059, as well as the complemented strain P-1059C. And the ability of the acapsular mutant ΔhexB to induced protection against wild-type challenge in chickens. Electron microscopy examination of the ΔhexB showed the absence of capsular material compared to the P-1059 and P-1059C. The ΔhexB was sensitive to the bactericidal action of chicken serum, whereas the P-1059 and P-1059C were both resistant. The ΔhexB was highly attenuated in chickens by intravenously injection, and intramuscular administration of ΔhexB to chickens stimulated significant protection against P-1059 and the homologous strain X-73(A:1). These results demonstrated that the capsule is a major virulence factor of Pasteurella multocida serotype A:3 strains.
Highlights
Pasteurella multocida causes fowl cholera in turkeys and chickens, and many avian species, and hemorrhagic septicemia in cattle and buffalos, and atrophic rhinitis in swine
A spontaneous noncapsulated mutant P-1059B obtained from 35 serial passages of P. multocida strain P-1059, demonstrated that the loss of ability to produce capsular materials resulted in a marked loss of virulence [7]
The entire capsule locus of avian P. multocida X-73 (A:1) was cloned and sequenced, and the locus was divided into three regions, the region 1 of which contains four genes, hexD, hexC, hexB and hexA are predicted to encode proteins responsible for transport of the polysaccharide to the bacterial surface [11]
Summary
Pasteurella multocida causes fowl cholera in turkeys and chickens, and many avian species, and hemorrhagic septicemia in cattle and buffalos, and atrophic rhinitis in swine. The capsule of P. multocida type A is most often associated with avian cholera, and functions as a virulence factor, and it is composed largely of hyaluronic acid [1,2]. The capsulated strain of P. multocida treated with hyaluronidase became complementsensitive and were more readily phagocytosed in comparison with untreated capsulated strain [10] These studies have suggested that the capsular hyaluronic acid is a key virulence factor of P. multocida type A strains. Because these strains were not genetically defined, it is not possible to ascribe definitively their phenotypes to the lack of capsule. We constructed an acapsular mutant of P. multocida P-1059 by homologous recombination, and pathogenicity in chickens and protective ability of the mutant strain were evaluated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
