Urinary tract infection (UTI) is one of the most common bacterial infectious disease in childhood. Renal scarring is an important complication of UTIs. Known risk factors for renal scarring are younger age, anatomic defects, delayed treatment, and causative pathogens other than Escherichia coli. The aim of this study was to compare the characteristics of clinical and laboratory features of UTI with E. coli to those with non-E. coli in infants.

We reviewed the medical records of 1,120 infants under 12 months of age who had been admitted for UTIs between January 1998 and December 2007. All patients who were diagnosed with UTIs were divided into two groups (E. coli and non-E. coli UTIs).

Three hundred twenty-four of 1,120 cases met the inclusion criteria. The number of E. coli and non-E. coli UTIs was 273 (84.3%) and 51 (15.7%), respectively. As compared to the non-E. coli UTI group, the E. coli UTI group was younger (3.59 vs. 4.47 months, P=0.008), a longer duration of pyuria (3.96 vs. 3.06 days, P=0.01), higher peripheral white blood cell counts (13.89 vs. 12.13x10(3)/mm3, P=0.043), and lower rates of high degree (III-V) vesico-ureteral reflux (P=0.005).

UTIs with E. coli might have more severe clinical features and a lower prevalence of high grade vesico- ureteral reflux than UTIs with non-E. coli. However, no difference was noted in the clinical response to antibiotic therapy between the two groups.