Invasion and translocation of uropathogenic Escherichia coli isolated from urosepsis and patients with community-acquired urinary tract infection.

Uropathogenic Escherichia coli (UPEC) strains are found in high numbers in the gut of patients with urinary tract infections (UTIs). We hypothesised that in hospitalised patients, UPEC strains might translocate from the gut to the blood stream and that this could be due to the presence of virulence genes (VGs) that are not commonly found in UPEC strains that cause UTI only. To test this, E. coli strains representing 75 dominant clonal groups of UPEC isolated from the blood of hospitalised patients with UTI (urosepsis) (n = 22), hospital-acquired (HA) UTI without blood infection (n = 24) and strains isolated from patients with community-acquired (CA)-UTIs (n = 29) were tested for their adhesion to, invasion and translocation through Caco-2 cells, in addition to the presence of 34 VGs associated with UPEC. Although there were no differences in the rate and degree of translocation among the groups, urosepsis and HA-UTI strains showed significantly higher abilities to adhere (P = 0.0095 and P < 0.0001 respectively) and invade Caco-2 cells than CA-UTI isolates (P = 0.0044, P = 0.0048 respectively). Urosepsis strains also carried significantly more VGs than strains isolated from patients with only UTI and/or CA-UTI isolates. In contrast, the antigen 43 allele RS218 was found more commonly among CA-UTI strains than in the other two groups. These data indicate that UPEC strains, irrespective of their source, are capable of translocating through gut epithelium. However, urosepsis and HA-UTI strains have a much better ability to interact with gut epithelia and have a greater virulence potential than CA-UPEC, which allows them to cause blood infection.