691 - Positive urine cultures for Enterococcus spp. vs. Escherichia coli in febrile infants younger than 90 days: a matched cohort study

Publication Number: 3668.691

Jose Antonio Alonso Cadenas, Hospital Infantil Universitario Niño jesús, Madrid, Madrid, Spain; María Suárez-Bustamante, Hospital Infantil Universitario Niño Jesús, Madrid, Madrid, Spain; Leticia Pérez, University of Oviedo, Bilbao, Pais Vasco, Spain; Cristina Ibarzo Port, Hospital Parc Taulí, Sabadell, Catalonia, Spain; Alexia Hernández Pernía, HOSPITAL INFANTIL UNIVERSITARIO NIÑO JESÚS, Madrid, Madrid, Spain; Andrea Trujillo, University of Basque Country, Portugalete, Pais Vasco, Spain; Santiago Mintegi Raso, Hospital Universitario Cruces, Bilbao, Pais Vasco, Spain; Roberto Velasco, Hospital Universitari Parc Taulí, SABADELL, Catalonia, Spain; Borja Gómez, Hospital Universitario Cruces, Barakaldo, Pais Vasco, Spain

Background: Escherichia coli is the leading cause of positive urine cultures (UC) in febrile infants younger than 90 days, whereas Enterococcus spp. is less common and often not associated with leukocyturia. The clinical significance of Enterococcus spp. isolation without inflammatory response in this age group remains uncertain, and it is controversial whether it represents asymptomatic bacteriuria or contamination, or a true urinary tract infection (UTI) with a false-negative urinalysis.

Objective: To compare the characteristics of positive UCs by Enterococcus spp. and E. coli in febrile infants ≤90 days old, according to urine dipstick results.

Design/Methods: We conducted a multicenter, retrospective matched-cohort study including febrile infants ≤90 days old with positive UC (growth of ≥10,000 cfu/ml in catheterized samples or ≥100,000 cfu/ml in clean-catch samples) for Enterococcus spp. or E. coli (1:1 matched by age and sex) attended in three pediatric emergency departments between 2011 and 2023. Demographic, clinical, laboratory, imaging, and one-year follow-up data evolution were compared based on the absence or presence of associated leukocyturia in the urine dipstick. UTI was defined as a positive UC with associated leukocyturia.

Results: Tables 1 and 2 compare the two groups according to their urine dipstick results. No significant differences were found in clinical presentation or short-term management. Infants with leukocyturia had higher blood biomarkers values than those with normal urine dipstick, regardless of the isolated pathogen. Infants with UTIs caused by Enterococcus spp. showed a higher rate of recurrent UTI and abnormal findings in voiding cystourethrography and dimercaptosuccinic acid scans compared to E. coli UTIs.

Conclusion(s): UTIs due to Enterococcus spp. in febrile infants younger than 90 days are more often linked to urinary tract abnormalities, recurrences, and kidney injury than E. coli infections. When Enterococcus spp. is isolated without inflammatory response (normal dipstick), the likelihood of a true UTI based on dimercaptosuccinic acid scans results is low but higher than with E. coli, and it may still behave more aggressively. These findings may help guide the interpretation and management of Enterococcus spp. isolation in young febrile infants.

Table 1. Comparison between infants with a positive urine culture for Enterococcus spp. or Escherichia coli according to the result of the urine dipstick test.
1Anteroposterior diameter of the renal pelvis <10 mm. 2Anteroposterior diameter of the renal pelvis ≥10 mm or with additional urinary anomalies.
UTI, urinary tract infection; WBC, white blood cell count; CRP, C-reactive protein; PCT, procalcitonin; IQR, interquartile range.


Table 2. Abnormal findings in the tests performed in infants with positive urine culture according to urine dipstick results and causative pathogen.
1 Postnatal renal ultrasound was considered abnormal when classified as UTD P2-P3 that is, when the anteroposterior renal pelvic diameter (APRPD) was ≥15 mm or when any of the following findings were present: peripheral calyceal dilatation, parenchymal thinning or increased echogenicity with loss of corticomedullary differentiation, visualization of a dilated ureter, or bladder abnormalities such as wall thickening, ureterocele, or posterior urethral dilatation.
2 DMSA was considered abnormal when showing focal cortical defects, diffuse inhomogeneous tracer uptake, or a differential renal function <40% in one kidney.
3 On VCUG, vesicoureteral reflux was graded from I to V according to the international classification and considered pathological from grade II onward.

DMSA, dimercaptosuccinic acid; VCUG, voiding cystourethrography.