Corresponding Author: Moslehi Mohammad Ashkan, MD, Department of Pediatrics, Nemazee Hospital, Shiraz University of Medical Sciences, Shiraz , Iran. E-mail: moslehim@sums.ac.ir

INTRODUCTION

Urinary tract infection (UTI) in newborns is one of most clinical problem that frequently is associated with bacteremia and may produce long-term complications. Newborns that label as have UTI should be admitted in hospital and further workup for evaluation for associated systemic infection and anatomic or functional abnormalities of the urinary tract must be done. The epidemiology, pathogenesis, clinical features, diagnosis, and management of UTIs in newborns are reviewed here.

EPIDEMIOLOGY

In normal term newborns, the incidence of bacteriuria determined by prospective bladder urine collection (suprapubic aspiration) is 0.1 to 1 percent.2-9 The risk of significant bacteriuria may be higher in high-risk newborns. 3 In premature infants, the incidence of bacteriuria is 2 to 6 percent ^{3, 4, 7, 8}. UTI occurs in 1.5 to 5 times as many males as females in the neonatal period and is higher in uncircumcised than circumcised males ^{3, 6, 10, 11}. The incidence decreases in boys and increases in girls during the first six months after birth.¹² It is approximately three times more common in females than males by one year of age. The higher incidence in neonatal males also appears to occur in preterm infants .4, 9, 13 UTI typically presents in the second week after birth in term infants and somewhat later in preterm infants .^{3, 9, 11} This infection is an unusual occurrence during the first three days after birth.^{14, 15}

Escherichia coli is the most common organism isolated in the newborn period, accounting for up to 80 percent of infections in most large series.^3,6,16,17 This pathogen also is the most frequent cause of UTI at all ages. Other Enterobacteriaceae, which can produce UTI, include: Klebsiella, Enterobacter, Citrobacter, Proteus, Providencia, Morganella, Serratia, and Salmonella species.

Fungal infections (predominantly Candida species) occur commonly in premature infants. Gestational and postnatal ages were lower in infants with Candida compared to bacterial infections .¹⁸

Several virulence factors in E. coli account for the propensity of this organism to cause UTI, especially when the urinary tract is anatomically normal.¹⁷

Factors that affect the virulence of E. coli include:

• Bacterial fimbriae
 
• Bacterial flagella
 
• Production of a hemolysin (induces formation of pores in the cell membrane), aerobactin, siderophore (necessary for iron acquisition in the iron-poor environment of the urinary tract).