Urine culture obtained from bag specimens and suprapubic aspiration in neonates

Abstract

Obtaining uncontaminated urine samples are important to diagnosis urinary tract infection in neonates. The present study was designed to compare urine contamination rates in two common methods of urine collection: urine bag versus suprapubic aspiration. In a cross-sectional study, 119 consecutive infants (aged 3 to 28 days) with fever who were referred to Children’s Hospital Medical Center in Tehran between September 2004 and March 2005 were included. Urine was collected simultaneously by bag and suprapubic aspiration. The urine samples were analyzed and bacterial cultures performed using standard bacteriologic techniques. The rate of culture contamination differed markedly according to the method of urine culture. Suprapubic aspiration specimens were sterile in 92.4%. Pathogenic bacteria were isolated in 7.6%. No bacterial isolates were deemed to be contaminants. Only 8.5% of bag specimens were sterile. Of non-sterile cultures, 36.9% of bacterial isolates were deemed to be pathogenic and 54.6% contaminants (P < 0.001 vs. suprapubic aspiration). Pyuria (P = 0.002) and bacteriuria (P < 0.001) were more frequent in specimens obtained by bag than urine from suprapubic aspiration. The existence of a urinary tract anomaly was the main predictor for a positive culture in urine obtained by suprapubic aspiration. Contamination rates and rates of pyuria and bacteriuria are remarkably higher for urine obtained by bag specimens than for urine obtained by suprapubic aspiration.

Keywords

Urinary tract infection - contamination - urine culture - neonate