The Pediatric Infectious Disease Journal •  Volume 33, Number 6, June 2014 www.pidj.com | 571 ORIGINAL STUDIES Background: Urinary tract infection (UTI) is the most frequent severe bac- terial infection in infants. Up to 31% of infants with UTI have bacteremia. Methods: We retrospectively identified all infants aged 0–2 months who were managed in our hospital with UTI during a 1-year period. Those with bacteremia were compared with those without bacteremia, according to the following variables: ethnicity, age, gender, white blood cell and polymor- phonuclear counts, C-reactive protein, urinalysis and blood creatinine val- ues as related to age-appropriate norms, imaging and outcome. Results: We identified 81 infants with 82 episodes of UTI. Most occurred in males (72.8%) and 35 (42.7%) were in infants of non-Jewish origin. In 14/81 (17.3%) of episodes, Escherichia coli was cultured from blood. In multivariate analysis, increased blood creatinine levels (P = 0.004) and non-Jewish origin (P = 0.006) were associated with bacteremia. Time to defervescence was significantly longer in bacteremic versus nonbacteremic children (P = 0.018). Duration of hospitalization was longer in bacteremic infants—10 (7–17) days in bacteremic versus 7 (1–14) days in nonbactere- mic children (P < 0.001). Conclusions: In infants aged 0–2 months with UTI, increased blood creati- nine value at admission was associated with bacteremia. This value provides an additional clue on admission, independent of personal judgment, to help identify infants at higher risk for bacteremia, prolonged hospitalization and possible complications. Key Words: urinary tract infection, neonates, bacteremia, renal function (Pediatr Infect Dis J 2014;33:571–575) U rinary tract infection (UTI) is one of the most common causes of serious bacterial infections in infants <90 days of age. UTI occurs in 0.1–1% of term neonates 1–4 and is a cause of fever in 5–13.6% of febrile infants <8 weeks of age. 5–9 One study found that 85% of serious bacterial infections in infants <90 days of age resulted from UTI. 10 In children with UTI, the rate of concurrent bacteremia has been reported as 0–31%. 5,11–16 Identification at presentation of infants who will subse- quently be diagnosed with bacteremia may enable identification of those prone to complications. 15 The purpose of this study was to identify risk factors at presentation associated with bacteremia in febrile infants aged 0–60 days. MATERIALS AND METHODS Study Design We conducted a retrospective cohort study in which we identified all infants aged 0–2 months admitted to the pediatric emergency room at the Hadassah-Hebrew University Medical Center during a period of 1 year (2007), with subsequent positive urine cultures. The microbiologic data of our hospital are comput- erized and the WHOnet search tool was used to identify patients with positive urine cultures. After identifying all patients, clinical data were extracted from their medical records. Our institutional policy of urine culture sampling in this age group is to draw the specimen by either suprapubic aspiration (SPA) or sterile urine catheter in all infants with fever or other complaints that may be compatible with UTI—among them, unexplained pro- longed/nonresolving vomiting and/or prolonged unexplained jaun- dice or failure to thrive. Duration of fever was determined in blocks of 8 hours, which is the standard temperature measurement interval in our hospital. Obtaining blood cultures is a routine procedure in every infant up to 2 months of age with suspected bacterial infection. The standard volume of blood obtained for the blood cultures at this age in our hospital is 0.5–1.5 mL blood added to each aerobic and anaerobic bottle. Biochemical analyses of leukocyte esterase and nitrite in urine was performed through a rapid dipstick method. A urine microscopic examination for white blood cells (WBCs) and bacteria was performed routinely if the volume of urine was suffi- cient for both culture and urinalysis. All imaging was assessed by a pediatric radiologist with over 10 years’ experience. The study was approved by Hadassah-Hebrew University Medical Center’s Ethics Committee. Definitions Infants were classified as having a UTI if they met the fol- lowing criteria: clinical symptoms of infection (fever, vomiting, poor feeding, jaundice, failure to thrive or diarrhea) together with any pathogen growth from the urine sample obtained by SPA or ≥10 4 colony forming units (CFU)/mL with a single pathogen from urine obtained by catheterization. 17 Bacteremia was defined as growth of a pathogen in the blood culture. UTI accompanied by bacteremia was defined when the same bacterium, with identical in vitro antibiotic susceptibility pattern, was cultured from both blood and urine. Abnormal body tempera- ture was defined as hyperthermia (>38°C) or hypothermia (<36°C). Abnormal WBC count was defined as leukopenia or leukocytosis, and abnormal polymorphonuclear count was defined according to age-related norms. 18 Abnormal levels of C-reactive protein (CRP) were >0.5 mg%. Cerebrospinal fluid (CSF) pleocytosis was defined as WBC in CSF above 32 cells/mm 3 in infants <30 days of age and >10 cells/mm 3 in infants >30 days. 19,20 Increased blood creatinine was defined as creatinine level above the 50th percentile for age. 21 Patient Selection The charts of all infants <2 months of age brought to the pediatric emergency department and diagnosed with UTI were Copyright © 2014 by Lippincott Williams & Wilkins ISSN: 0891-3668/14/3306-0571 DOI: 10.1097/INF.0000000000000316 Factors Associated With Bacteremia in Young  Infants With Urinary Tract Infection Diana Averbuch, MD,*† Ran Nir-Paz, MD,‡ Ariel Tenenbaum, MD,§ Polina Stepensky, MD,* Rebecca Brooks, MD,§ Benjamin Z. Koplewitz, MD,¶ Ari M. Simckes, MD,*‖ and Dan Engelhard, MD*†** Accepted for publication November 14, 2013. From the *Department of Pediatrics, Ein Kerem, †Pediatric Infectious Dis- eases Unit, ‡Department of Clinical Microbiology and Infectious Diseases, §Department of Pediatrics, Mount Scopus, ¶Department of Medical Imag- ing, and ‖Pediatric Nephrology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; and **School of Primary Health Care, Monash University, Melbourne, Victoria, Australia. This study was presented at the ICAAC Conference, 2008. The authors have no funding or conflicts of interest to disclose. Address for correspondence: Diana Averbuch, MD, Pediatric Infectious Dis- eases Unit, Hadassah-Hebrew University Medical Center, Ein Kerem, Kiryat Hadassah, P.O.B. 12000, Jerusalem, 91120, Israel. E-mail: adiana@hadas- sah.org.il, dina8282@walla.co.il.