Isolation and Virulence Evaluation of Currently Circulating Avibacterium paragallinarum in Poultry

Abstract

Avibacterium paragallinarum is a Gram-negative bacterium that causes infectious coryza (IC), a respiratory disease that is highly contagious among chickens. Through PCR testing and sequence analysis of the FlfA gene, a total of 10 Av. paragallinarum field isolates were identified, accounting for 5.7% of the samples. In this study, we assessed the virulence of field isolates by utilizing a rapid artificial intrasinus injection route model. Upon observation, we have found that all 10 field isolates from Egypt that were identified as type B strains possess virulent properties and have the ability to cause Infectious Coryza (IC) disease in chickens. The current study aimed to sequence the FlfA gene and conduct phylogenetic analyses to better understand the Avibacterium paragallinarum field isolates that have been circulating in Egypt in recent years. This research will provide valuable insights into the genetic makeup and evolution of this pathogen, which can inform future efforts to control and prevent its spread. The amino acid sequences of Avibacterium paragallinarum from Egypt and the reference sequence exhibit a remarkable degree of homology, ranging from 97.96% to 100%. This finding underscores the close relationship between the two sequences and highlights the potential for further research into the genetic makeup of this pathogen. Furthermore, the discovery of a fimbrial cluster that is identical to the Galli bacterium FlfA in the Av. paragallinarum genome indicates that these two species may have recently exchanged this fimbriae. This exchange could have occurred during the natural co-colonization of the chicken's upper respiratory tract. It is possible that this exchange could have implications for the pathogenicity and virulence of these bacteria. The FlfA protein has unique characteristics and was subjected to bioinformatics analysis to predict its properties and protein interactions. The FlfA protein structure is stable with many coiled regions. ..