Effects of the type V secretion system eYadA on the biological properties and pathogenicity of avian pathogenic Escherichia coli.

Avian pathogenic Escherichia coli (APEC) mainly causes local or systemic infections in chickens, ducks, and other avian species. These infections clinically present as various types of inflammation and septicemia, resulting in significant economic losses in the poultry industry. The type V secretion system (T5SS) is prevalent in APEC and serves a crucial role as a virulence factor during the infection process. Trimeric autotransporter adhesins (TAAs), which belong to the Vc subtype of T5SS, are proteins located on the outer membrane of Gram-negative bacteria. Yersinia adhesin A (YadA) is an important model for studying TAA structure, function, and biogenesis; it has also been proven to be a significant virulence factor in other Gram-negative bacteria. To explore the role of eYadA, an autotransporter adhesin belonging to the YadA family, in the pathogenesis of APEC, we constructed both an eyadA deletion strain and its complemented strain. We analyzed their biological characteristics and pathogenicity and found that eyadA influences motility and biofilm formation in APEC as well as its pathogenicity towards both mice and ducklings. Furthermore, it affects the regulation of inflammatory cytokines; changes in these cytokine levels were found to correlate with both infection dose and duration of exposure. This study provides new insights into understanding the pathogenic mechanisms associated with APEC while also suggesting effective strategies for prevention and control measures against this pathogen.