Abstract
Urinary pathogenic Escherichia coli (UPEC) are the most common pathogens causing recurrent urinary tract infections (rUTI) in women, a common debilitating infection. Studies so far into its pathogenesis have identified an array of putative urovirulence factors or genes necessary for functions such as bacterial adhesion to bladder epithelial cells, iron uptake mechanisms and toxin production as potential targets for vaccine development or treatment strategies. Yet, treatment is largely limited to use of antimicrobial therapy.
The aim in this study was to examine the differences in genotypic as well as phenotypic characteristics of E. coli isolates collected from 132 patients from three patient cohorts – those with rUTI, sporadic UTI (sUTI), and non-urinary sources of E. coli infection (nUTI). Genotypic characteristics investigated using whole genome sequencing revealed that phylogroup B2 carried more virulence genes than phylogroups B1 (p = 0.034) and phylogroup D (p = 0.004). However, no significant differences in genotypic characteristics could be detected when the virulence gene carriage between the 3 patient cohorts were compared. High throughput carbon utilization phenotypic microarray (PM) assays (Biolog, Inc.), used to compare the phenotypic profiles, which included common host metabolites such as L-serine and D-serine, detected no differences between patient cohorts or phylogroups.
One isolate from a patient with sporadic UTI, however, was noted to exhibit no metabolic activity on PM tests. This was identified as a small colony variant (SCV), which, are associated with recurrent and chronic infections. Its phenotypic and genotypic characteristics were explored which showed that its profile did not match any of the previously reported genotypes or phenotypes associated with E. coli SCV. A unique SCV has been identified and further work is necessary to understand the factors contributing to this morphology which may be key to unravelling as yet unidentified mechanisms for the ability of E. coli to cause recurrent infections.