Research Note: Isolation and genomic characterization of Avibacterium paragallinarum from the Hubei Province, China.

Infectious coryza (IC), caused by Avibacterium paragallinarum, is a major respiratory disease in chickens. It causes growth retardation in broilers and reduced egg production in layers, ultimately leading to huge economic losses to the poultry industry. In this study, we aimed to investigate the prevalence and genetic characteristics of 12 A. paragallinarum strains isolated from Hubei Province in 2022-2023. Whole-genome sequencing and average nucleotide identity analysis demonstrated close phylogenetic relationships between the isolates and domestic reference strains. Serotyping using the hemagglutination inhibition test identified six strains as serovar A, four as serovar B, and two as serovar C. All isolates were nicotinamide adenine dinucleotide-dependent. Antimicrobial susceptibility testing revealed that all isolates exhibited resistance to tetracycline and lincomycin and sensitivity to levofloxacin. The isolates demonstrated varying degrees of resistance to other antibiotics, including erythromycin, doxycycline, cefotaxime, florfenicol, polymyxin B, spectinomycin, and amikacin. Pathogenicity analysis revealed a wide range of virulence among the isolates, from completely virulent (100 %) to avirulent (0 %). Additionally, 14 categories of antibiotic-resistance genes, including peptide antibiotic-resistance genes, and 12 categories of virulence genes, such as adherence factor genes, were predicted using the CARD and VFDB databases. Notably, no genetic divergence was detected in resistance or virulence determinants among the 12 isolates. Overall, our study provides valuable data for the clinical management of A. paragallinarum and offers insights into its pathogenicity and antibiotic-resistance mechanisms for future studies.