Abstract
Pasteurella multocida (P. multocida) is an animal pathogen of worldwide economic significance that causes fowl cholera in poultry and wild birds. Global gene regulators, including PhoP are important in regulating bacterial virulence and are good targets for developing attenuated vaccines against many pathogenic bacteria. However, the biological significance of phoP gene has not been identified in P. multocida. Here, we identified the phoP gene in P. multocida, and we evaluated the roles of phoP in P. multocida by deleting the phoP gene. The P. multocida phoP mutant exhibited similar growth curves and lipopolysaccharide and outer membrane protein profiles but displayed defective polymyxin resistance in vitro compared with the parent strain. Additionally, the phoP deletion resulted in decreased virulence. The LD50 of the ΔphoP mutant was 32- and 154-fold higher than the parent strain via the oral and intranasal routes, respectively. Transcriptome sequencing analysis showed that 161 genes were up-regulated and 173 genes were down-regulated in the absence of the phoP gene. Finally, the immunogenicity and protective efficacy of the ΔphoP mutant were evaluated. Immunized ducks produced significantly higher levels of serum IgY and bile IgA compared to the control ducks, and immunization with the ΔphoP mutant conferred 54.5% protection efficiency against challenge with the virulent P. multocida. This work provides a platform to dissect the function of phoP and develop a new vaccine against P. multocida.
Highlights
Pasteurella multocida (P. multocida) is a Gram-negative encapsulated bacterium that is the causative agent of a range of animal pasteurellosis diseases, including fowl cholera in poultry and wild birds, hemorrhagic septicemia in cattle and buffalo, atrophic rhinitis in swine, and snuffles in rabbits [1]
The proteins encoded by the phoP1 and phoP2 gene shared 27.23% and 36.53% identity with the PhoP of Salmonella enterica serovar Typhimurium
Asd is required for the synthesis of diaminopimelic acid (DAP), an essential component for biosynthesis of
Summary
Pasteurella multocida (P. multocida) is a Gram-negative encapsulated bacterium that is the causative agent of a range of animal pasteurellosis diseases, including fowl cholera in poultry and wild birds, hemorrhagic septicemia in cattle and buffalo, atrophic rhinitis in swine, and snuffles in rabbits [1]. Fowl cholera is a severe systemic disease that occurs in domestic poultry and wild birds and results in significant economic losses to poultry industries worldwide [2]. Vaccination of fowl would provide protection against P. multocida infection [4]. Current vaccines against fowl cholera include bacterins and live attenuated vaccines: the former provides only limited protection against homologous serotypes, and the latter were developed empirically and were observed to revert to the virulent strain [4]. There is a pressing need to develop new vaccines, especially well-defined live vaccines for fowl cholera control
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