title: Contamination of urinary cultures in initial-stream versus later-stream urine in children undergoing bladder catheterization for the diagnosis of urinary tract infection.
abstract: BACKGROUND
  Urine cultures obtained by bladder catheterization can be contaminated by bacteria colonizing the distal urethra. Data are inconclusive regarding the potential advantage of discarding the first few urine drops obtained by bladder catheterization and testing only the sample of late-stream urine, thus reducing the likelihood of urine culture contamination.
  
  
  OBJECTIVE
  The aim of this study was to evaluate whether the incidence of contaminated urine cultures obtained by bladder catheterization can be reduced by splitting urine samples into 'initial' and 'late' samples and using only 'late' samples for culture.
  
  
  METHODS
  Urine samples obtained by bladder catheterization from children younger than 2 years being evaluated for urinary tract infection were prospectively collected. Quantitative culture results were compared between initial-stream and late-stream urine samples.
  
  
  RESULTS
  A total of 199 urine culture pairs of initial and late samples were compared. When using a cutoff value of at least 10 000 colony forming units/ml, late samples were superior to the initial ones in reducing contamination of urine cultures (P=0.029).
  
  
  CONCLUSIONS
  When obtaining urine cultures by bladder catheterization in children younger than 2 years, discarding the first few urine drops and using only the late stream for culture reduces false-positive culture results and improves the accuracy of urinary tract infection diagnosis.
authors.affiliation: aDepartment of Pediatrics bInfectious Diseases Unit cPediatric Nephrology Unit dPediatric Emergency Unit, Shaare Zedek Medical Center affiliated with Hebrew University-Hadassah School of Medicine, Jerusalem, Israel.
authors.forename: Orli
authors.initials: O
authors.lastname: Megged
authors.forename: Liron
authors.initials: L
authors.lastname: Zilberstein
authors.forename: Efrat
authors.initials: E
authors.lastname: Ben Shalom
authors.forename: Matityahu
authors.initials: M
authors.lastname: Erlichman
mesh_terms: D002675:Child, Preschool; D015331:Cohort Studies; D004866:Equipment Contamination; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D012189:Retrospective Studies; D018570:Risk Assessment; D014521:Urethra / Q000382:microbiology*; D014546:Urinary Catheterization / Q000379:methods*; D014552:Urinary Tract Infections / Q000175:diagnosis* / Q000382:microbiology; D059349:Urine Specimen Collection / Q000379:methods*