Virulence factors and biofilm production among Escherichia coli strains causing bacteraemia of urinary tract origin

The aim of the present study was to gain an insight into the role of virulence determinants and biofilm production in bacteraemia of urinary tract origin. For this purpose 105 Escherichia coli isolates from patients with bacteraemia of urinary tract origin, isolated at the Institute of Microbiology and Immunology, University of Ljubljana, Slovenia, were investigated. A total of 88 strains (84%) were isolated from immunocompromised patients and 17 (16%) from non-immunocompromised patients. The prevalence of virulence factor (VF)-encoding genes and associations with phylogenetic background, antibiotic resistance, biofilm production and patient status were analysed by PCR and bioassay. Biofilm was produced by 55 (53%) of the strains. No combination of VFs was highly associated with biofilm production. Of the tested VF-encoding genes, usp, papC and the adhesin-encoding sfa/foc were significantly more prevalent among strains from non-immunocompromised patients. Our results indicate that the uropathogenic specific protein (USP) may be, as judged by predominance and associations of the usp gene, an important VF contributing significantly to bacteraemia of urinary tract origin.