Urinary tract infection (UTI) is the most common genitourinary tract disease and the second most common bacterial infection following respiratory tract infections, in childhood. Gram negative bacteria are the most common cause of urinary tract infection that may affect the upper or lower urinary tract [1]. Urinary tract infection occurs in 3-5% girls and 1% boys [2]. Studies have shown that the prevalence of UTI is greater than that of bacterial meningitis, bacterial pneumonia, middle ear infection and bacteraemia. During infancy, 5% of febrile girls and 20% of uncircumcised febrile boys are presented with UTI. Additionally, 80-90% of UTI are characterized by Escherichia Coli infection [1]. Vitamin D plays an important role in regulating inflammation, chemokine production and has been long known for its antimicrobial properties. Vitamin D receptors are widely expressed in immune cells such as B and T lymphocytes, monocytes, and dendritic cells where, it exerts immune modulatory effects. Circulating vitamin D has a direct effect on macrophages, enhancing its oxidative ability, including the synthesis and production of cytokines, phosphatase, and hydrogen peroxide. Vitamin D also accelerates neutrophil motility and phagocytic activity. During bacterial infections, macrophages convert 25-hydroxyvitamin D (25OHD) into circulating vitamin D3 [1, 25(OH)2D3], where it modulates the gene expression of antimicrobial peptides[8]. These peptides play a key role in the body's defense against the microbial pathogens. It enhances both the immune response and the clearance of bacteria. Several studies have revealed a link between vitamin D deficiency and urinary tract infections.
