Identification of Fur in Pasteurella multocida and the Potential of Its Mutant as an Attenuated Live Vaccine.

Qing Liu,Pei Li,Qingke Kong,Yunlong Hu

doi:10.3389/fvets.2019.00005

Qing Liu, Pei Li + Show 2 more

Open Access

https://doi.org/10.3389/fvets.2019.00005

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Abstract

Pasteurella multocida is a pathogenic microorganism that causes a variety of serious diseases in humans and animals worldwide. The global regulator gene, fur, plays an important role in pathogenesis and regulates the virulence of many bacteria. Here, we identified a fur gene in P. multocida by complementing a Salmonella Choleraesuis Δfur mutant, and characterized a fur mutant strain of P. multocida. The P. multocida Δfur mutant strain exhibited no significant differences in growth and outer membrane protein (OMP) profiles when the complemented strain was compared to the parent. Ducks were used as the model organism to determine the virulence and protection efficacy induced by Δfur mutant strain. Animal experiments showed that colonization by the mutant was decreased by oral infection of live Δfur mutant strain. The LD50 of the ducks infected with the Δfur mutant was 146-fold higher than that of the ducks infected with the wild-type strain when administered through the oral route. Evaluation of the immunogenicity and protective efficacy of the Δfur mutant of P. multocida revealed strong serum IgY and bile IgA immune responses following oral inoculation with the Δfur strain. Ducks that were orally inoculated with the Δfur mutant strain demonstrated 62% protection efficacy against severe lethal challenge with the wild-type P. multocida. This study provides new insights into P. multocida virulence and the potential use of an attenuated vaccine against P. multocida.

Highlights

Iron is an essential limiting element in bacterial metabolism, and its availability plays a vital role in the pathogenesis of most bacteria [1]
P. multocida was cultured in Bacto brain heart infusion (BHI) broth (BD Bioscience, San Jose, CA, USA), and Salmonella Choleraesuis and Escherichia coli were grown in Luria-Bertani (LB) broth
Choleraesuis were complemented with the recombinant plasmid pSS908 carrying the P. multocida fur gene in the low-copy-number plasmid pSS664

Summary

Introduction

Iron is an essential limiting element in bacterial metabolism, and its availability plays a vital role in the pathogenesis of most bacteria [1]. Many enzymes require iron as a necessary co-factor for a wide variety of physiological processes [2], such as respiration, DNA biosynthesis, gene regulation, and the tricarboxylic acid (TCA) cycle [3]. Proteins such as iron-containing heme and iron-sulfur cluster proteins act as excellent electron carriers and as environmental or intracellular sensors that regulate gene expression [4]. Iron is an enhancer of oxygen toxicity because this metal efficiently catalyzes the Fenton reaction, which converts hydrogen peroxide to the highly reactive hydroxyl radical [5].

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