Virulence factors in uropathogenic E. coli.

Escherichia coli isolates from urinary tract infections often exhibit characters different from those isolated from normal faecal samples. Adherence to uroepithelial cells, nature of lipopolysaccharide O antigen and mannose resistant haemagglutination of human erythrocytes are some of the important virulence factors proposed in the pathogenesis of urinary tract infections caused by E. coli. In the present study a total of 100 strains of E. coli isolated from symptomatic cases of urinary tract infections (with significant bacteriuria) were studied for these properties. Faecal isolates of E. coli from adult healthy individuals were also studied as controls. As many as 58 uropathogenic strains showed high affinity for attachment to uroepithelial cells while 28 strains showed adherence at moderate degree. Agglutination of human erythrocytes was induced by as many as 70 uropathogenic strains while in 32 strains haemagglutination was not affected by D-mannose. In control group, adherence was observed in eight strains while 28 strains were haemagglutinating. Of these 28 strains, D-mannose resistant haemagglutination was observed in only one faecal strain. In uropathogenic group O4 was isolated with maximum frequency (12%) followed by O101, O135 and O6.