Does Escherichia coli have pathogenic potential at a low level of bacteriuria in recurrent, uncomplicated urinary tract infection?

Abstract

BackgroundIn recurrent uncomplicated lower urinary tract infection (uLUTI), bacteriuria below 103 colony-forming units (CFU)/mL is not usually investigated. ObjectiveTo determine the molecular-genetic characteristics of the pathogenic potential of Enterobacteriaceae isolated between episodes of recurrent uLUTI at bacteriuria of 102 CFU/mL. Materials and methodsMidstream urine samples taken from 169 women between episodes of recurrent uLUTI were examined on six media. Fifteen Enterobacteriaceae strains at a low level of bacteriuria (102 CFU/mL) were analysed by polymerase chain reaction for the presence of the following virulence factor genes (VFGs): papA, papE/F, papGII, afa, bmaE, iutA, feoB, fyuA, kpsMTII and usp. ResultsAll 169 patients had leukocyturia and asymptomatic bacteriuria, and 62 of these cases were due to enterobacteria: 102 CFU/mL, 15 strains (24.2%); 103 CFU/mL, 10 strains (16.1%); and >103 CFU/mL, 37 strains (59.7%). VFGs were verified in all 15 strains at a low level of bacteriuria (102 CFU/mL): one VFG (papGII) was found in two strains of Klebsiella spp., three VFGs were found in one strain of Enterobacter spp.xst, and between four and nine VFGs were found in the remaining 12 strains. Among the VFGs, papGII (93.3%), usp (86.7%), feoB (80.0%), fyuA (80.0%) and kpsMTII (73.3%) predominated. A significant correlation was found between the presence of papE (P=0.02) and usp (P=0.025) and a relapse rate of more than four recurrences in 1 year. An association was found between leukocyturia and the presence of papE (P=0.031) and papGII (P=0.031). ConclusionEnterobacteria isolated from the urine of female patients with recurrent uLUTI at a low level of bacteriuria (102 CFU/mL) have a wide spectrum of VFGs, which may play a role in maintaining chronic inflammation of the lower urinary tract.