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E.coli in chronically colonized neurogenic bladders have fewer genetic markers of pathogenicity
John Kryger, MD1, Alex Burleigh, MS2, Melissa Christensen, CCRC1, Walter Hopkins, PhD2.
1Children's Hospital of Wisconsin, Milwaukee, WI, USA, 2University of Wisconsin, Madison, WI, USA.

BACKGROUND: Rates of urinary tract infection (UTI) in patients with urinary diversions or neurogenic bladders are high. Patients who use urinary catheters also develop chronic bacterial colonization, which may become symptomatic. Characterizing the strain and pathogenicity of bacteria present in the urine of these patients may help clinicians understand the circumstances under which patients are more likely to experience symptomatic UTIs. Moreover, if one can determine which patients experience benign colonization of their bladders with non-pathogenic organisms, novel treatment strategies can be developed to implant symbiotic bacteria into the bladder which may mitigate future infections.
METHODS: Discarded urine collected for standard care was obtained from 80 patients seen at two Pediatric Urology practices. Samples were acquired from patients with neurogenic bladders, but only those who had not been on antibiotics within the last 90 days. Patients with augmented bladders were included. Bacteria present in urine were identified using eosin methylene blue and CHROMagar™ media. Escherichia coli (E.coli) isolates were analyzed using multiplex polymerase chain reaction (PCR) to define each strain’s phylotype and the presence of UTI-associated pathogenicity islands (PAI): I(CFT), II (CFT), I(J96), I(536), II(536), III(536), and IV(536). Each isolate was also tested for the presence of the following genes: hemolysin (hlyA), afimbrial adhesion (afa1), cytotoxic necrotizing factor (cnf1), S.fimbria (sfa), and type-1 fimbrial adhesin (FimH).

RESULTS: Of the 80 urine samples collected, 25 (31%) contained E.coli. Virulence factor (VF) profiles were completed on 16 of the E.coli samples. Very few of the isolates had A (3%) or D (0%) phylotypes, while 41% and 54% had B1 or B2, respectively. Only the I(CFT), II(CFT), and IV(536) PAIs were present in 75%, 31%, and 64% of the isolates, respectively. All strains had FimH, and none contained afa1.

CONCLUSIONS: These results underscore the heterogeneity of E.coli strain virulence in the bladders of pediatric patients who use urinary catheters. Of particular interst is the low incidence of several PAIs and the D phylotype typically found in uropathogenic E.coli. This information represents a critical first step in understanding the baseline milieu of neurogenic bladders. Future studies will focus on the pathogenicity of other colonizing organisms and explore how bacterial strain presence may change over time in these patients.

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