Enterococcal Surface Protein Transiently AggravatesEnterococcus faecium–Induced Urinary Tract Infection in Mice

The role that the enterococcal surface protein Esp plays in the capacity of Enterococcus faecium to adhere to uroepithelial cells and the role that it plays in urinary tract infection and peritonitis was investigated in vitro and in vivo, respectively, using Esp-expressing E. faecium (E1162) and its isogenic Esp-deficient mutant (E1162 Delta esp). Esp expression enhanced in vitro binding to bladder and kidney epithelial cells. In mice, higher numbers of E1162 were cultured from kidneys and bladders after the induction of urinary tract infection, compared with E1162 Delta esp numbers. This was accompanied by a higher frequency of bacteremia, higher cytokine levels in kidney tissue, and renal insufficiency. Esp had no effect on the course of E. faecium peritonitis.