Virulence Traits in Escherichia Coli Strains Isolated from Outpatients with Urinary Tract Infections

Abstract

This study aims to characterize phenotypic and genotypic virulence traits in Escherichia coli strains, isolated from outpatients with urinary tract infections, comparing with those obtained from inpatients. Information on the pathogenic behavior of the uropathogenic strains was obtained by monitoring different biological properties, such as autoagglutination, hemagglutination, adhesiveness to and invasion of human bladder (HT1376) cells, biofilm formation, phylogenetic grouping, and virulencerelated genes. The results show similar behavior in the two groups concerning autoagglutination, hemagglutination, and biofilm formation. None of the strains examined was invasive. However, in strains from outpatients there was an increased adhesion to HT1376 cells compared with clinical strains, a significant higher presence of genes codifying for adhesins and cell protection factors, and a lower proportion of strains belonging to Bl group. These findings add further information on the pathogenic traits of community E. coli, since strains isolated from the outpatients' group were differently "armed" in comparison with those of clinical cases, and more suitable to infect healthy individuals.Urinary tract infections (UTIs) are among the most common extraintestinal diseases in the developed world (I). Escherichia coli is by far the most common microrganism involved and isolated from about 50% of all nosocomial UTIs and 90% of outpatients (2). Urinary and commensal E. coli differ with respect to phylogenetic background and virulence (3). Phylogenetic analyses have shown that virulent E. coli clones, belonging to B2 and D groups (4-6), are preponderant in UTIs and possess specialized virulence factors conferring pathogenetic potential (3-4, 7). Molecular studies have contributed to the discovery ofthe determinants ofuropathogenic virulence that act in additive or synergic fashion, enhancing the cumulative impact of pathogenicity in UTIs (8-12). In fact, most uropathogenic E. coli strains exhibit definite virulence attributes, including adhesins, iron uptake systems, and synthesis of cytotoxins, that are lacking in commensal E. coli (II,(13)(14)(15).Adhesion of E. coli cells to uroepithelium, which may be associated with fimbrial structures, is a major feature of uropathogenic strains, since it protects the bacteria from urinary lavage, increasing their ability to colonize (16)(17). Following the selective adhesion to the mucosal uroepithelium or medical devices, E. coli cells grow as a biofilm and persist for a long time in the genitourinary tract, thus interfering with the chemioantibiotic therapy for bacterial eradication (18). Moreover, hemagglutination and aggregation,