Concentration of novel urinary tract infection biomarkers in neonates

Urinary tract infections (UTIs) are a common comorbidity in hospitalized neonates. The current UTI diagnostics have several limitations including invasive collection of urinary samples to ensure sterility, risk of contamination and lack of consensus definitions of UTI based on urine culture. Antimicrobial peptides (AMPs) have been recently utilized as novel biomarkers that can efficiently and accurately diagnose pediatric UTI. However, the concentration of AMPs in neonatal urine is not well-defined. Urine from neonates admitted to a single level IV neonatal intensive care unit was obtained to determine baseline concentration of two AMPs, Ribonuclease 7 (RNase 7) and Beta Defensin-1 (BD-1) and to define the relationship between AMP concentration and gestational age (GA). AMP levels were normalized to urine creatinine. RNase 7 and BD-1 were expressed in neonatal urine (n = 66) regardless of GA and as early as 22 weeks gestation. Urinary concentrations of both AMPs decreased as GA and birthweight increased. The overall median urinary RNase 7/UCr and BD-1/UCr values were 271 ng/mg, and 116 ng/mg, respectively. Median urinary concentrations of RNase 7/UCr for infants born at < 27, 27–32, 33–35 and ≥ 36 weeks were 569, 308, 254, and 124 ng/mg respectively. Similarly, the concentrations of BD-1/UCr at these GA were 166, 115, 108, and 14 ng/mg, respectively. Baseline neonatal urinary concentration of two AMPs (RNase 7 and BD-1) and the variation by GA were identified. This is an essential first step toward the potential utilization of AMPs in improving neonatal UTI diagnostics.