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

Background: In recurrent uncomplicated lower urinary tract infection (uLUTI), bacteriuria below 10 colony-forming units (CFU)/mL is not usually investigated.

Objective: To determine the molecular-genetic characteristics of the pathogenic potential of Enterobacteriaceae isolated between episodes of recurrent uLUTI at bacteriuria of 10 CFU/mL.

Materials And Methods: Midstream 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 (10 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.

Results: All 169 patients had leukocyturia and asymptomatic bacteriuria, and 62 of these cases were due to enterobacteria: 10 CFU/mL, 15 strains (24.2%); 10 CFU/mL, 10 strains (16.1%); and >10 CFU/mL, 37 strains (59.7%). VFGs were verified in all 15 strains at a low level of bacteriuria (10 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).

Conclusion: Enterobacteria isolated from the urine of female patients with recurrent uLUTI at a low level of bacteriuria (10 CFU/mL) have a wide spectrum of VFGs, which may play a role in maintaining chronic inflammation of the lower urinary tract.