Comprehensive Genomic Analysis of Two Avibacterium paragallinarum Strains with Significantly Different Virulence

Background: Infectious coryza, caused by Avibacterium paragallinarum, presents economic challenges to the global poultry industry. Previous research highlighted a highly virulent Av. paragallinarum strain (ZJ-C), which demonstrated a thousandfold increased virulence compared to a standard strain (Modesto) and evaded existing vaccine protection. This study aimed to conduct a comprehensive genomic analysis of two distinct Av. paragallinarum serogroup C strains, focusing on the pathogenic potential and resistance profiles. Methods: High-throughput sequencing technology was employed to assemble and analyze the genomic sequences of the ZJ-C (highly virulent) and Modesto (reference) strains. Comparative genomic analysis was facilitated by sophisticated tools like Mauve and BLAST Ring Image Generator and comprehensive databases such as the Virulence Factor Database and Comprehensive Antibiotic Resistance Database. Additionally, the virulence differences predicted by genomic analysis were experimentally validated using a chicken infection model. Result: The study identified variations in gene composition, including virulence genes, antibiotic resistance genes and metabolic pathways. Comparative analysis showed that the ZJ-C strain demonstrates increased resistance to antibiotics and higher infectivity compared to the Modesto strain. Unique virulence genes and resistance pathways in ZJ-C suggest evolutionary adaptability. Significant disparities in protein ortholog gene clusters and metabolic pathways were uncovered, indicating strain-specific adaptations. Animal infection experiments confirmed that the ZJ-C strain induced significantly more severe and prolonged clinical symptoms compared to Modesto, validating genomic predictions regarding virulence differences. Our findings offers valuable insights of the genomic landscape and pathogenicity of Av. paragallinarum, important for informing future vaccine research and disease control strategies. The study highlights the importance of genomic analysis in understanding pathogenicity, resistance profiles and host interactions of Av. paragallinarum, crucial for improving disease management in the poultry industry.