Does the presence of vesicoureteral reflux affect in vitro uropathogenic E. coli growth rate in urine?

Background: Uroepithelial molecules like uroplakins are involved both in the development of urinary tract and in colonization, attachment and invasion of uropathogenic Escherichia coli (UPEC). Uroplakin disorders are also associated with vesicoureteral reflux (VUR). We hypothesized that urine contents, as well as urinary flow, may be altered in VUR, and aimed to determine whether in vitro UPEC growth is increased in urine from the refluxing systems.
Methods: Children evaluated by voiding cystourethrography for UTI were enrolled. Groups 1 and 2 included children with and without VUR, respectively. Sterile urine samples were obtained from all patients, and 2 × 10(2) cfu/mL UPEC suspension was inoculated into these samples. After incubation for 24 h, colony counts were assessed. Both groups were compared for UPEC growth and colony counts.
Results: Forty-two urine samples were included (21 in each group). UPEC was cultured in 9 (43 %) and 3 (14 %) samples in Groups 1 and 2, respectively (p = 0.040, OR 4.5). Colony counts were similar in both groups (log x; 2.36 ± 0.25 vs. 2.37 ± 0.12, p = 0.923).
Conclusion: Inoculation of 2 × 10(2) cfu UPEC resulted in growth in almost half of the urine samples from refluxing systems, while UPEC growth was inhibited in most urine samples from non-refluxing systems suggesting that urine contents in refluxing units change in such a way that UPEC growth is facilitated.