**2. Adhesins of uropathogenic** *Escherichia coli*

Adhesins are adhesive organelles, notably fimbriae, that promote bacterial colonization. Some adhesins also promote bacterial invasion of the host cell. Adhesins are thought to be the most important virulence-associated molecules which function in UPEC pathogenicity. The adhesins can also directly trigger host and bacterial cell signaling pathways. They can also facilitate the delivery of other

bacterial products to the host tissues [17]. Prominent bacterial cell surface virulence factors, which play significant roles in UPEC pathogenicity include type 1 fimbriae [11]; Class I, Class II, and Class III of P-fimbriae [18–20]; Dr. family of adhesins for binding to the decay-accelerating factor (DAF) [21]; Curli fimbriae which functions as binding factor and biofilm producer [22]; and S-fimbriae [14, 23, 24]. Type 1 fimbriae have the most significant effects in UTIs as they enhance bacterial survival and growth, enhance inflammatory reaction at the mucosa, bacterial invasion, and control biofilm production [7]. P-fimbriae have the second most prominent role in UPEC-associated pathogenesis of human ascending UTIs and pyelonephritis. They promote UPEC adherence to the matrix of the mucosa and tissues and trigger cytokine production [25–30].
